Link: reviewed by Jason Thorpe on SoundStage! Ultra on October 1, 2023
General Information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The Fezz Audio Lybra 300B was conditioned for one hour at 1/8th full rated power (~2W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.
The Lybra offers three unbalanced (RCA) inputs and two pairs of speaker level outputs (one for 8 ohms, and one for 4 ohms). For the purposes of these measurements, the following input was evaluated: analog line-level input. Unless otherwise stated, when a measurement was made into an 8-ohm load the, 8-ohm speaker output was used, and for a 4-ohm (or 2-ohm) load, the 4-ohm speaker output was used. By default (if no load is mentioned), an 8-ohm load was used with the 8-ohm speaker outputs.
Most measurements were made with a 2Vrms line-level analog input. The signal-to-noise ratio (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 15W (8 ohms). For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum, but with a lower input voltage to achieve the same 15W output.
Based on the accuracy and non-repeatable results at various volume levels of the left/right channel matching (see table below), the Lybra volume control is a potentiometer operating in the analog domain. The volume control offers a total range from -75dB to +27.9dB for the 8-ohm output and 24.6dB for the 4-ohm output.
The analyzer’s input bandwidth filter was set to 10Hz–22.4kHz for all measurements, except for frequency response (DC to 1MHz), FFTs (10Hz to 90kHz), and THD vs. frequency (10Hz to 90kHz). The latter to capture the second and third harmonic of the 20kHz output signal. Since the Lybra is not a class-D amp, there was no issue with excessive noise above 20kHz.
Volume-control accuracy (measured at speaker outputs): left-right channel tracking
Volume position | Channel deviation |
min | 15dB |
7 o'clock | 1.77dB |
9 o'clock | 1.11dB |
10 o'clock | 0.633dB |
12 o'clock | 0.325dB |
1 o'clock | 0.308dB |
3 o'clock | 0.537dB |
4 o'clock | 0.518dB |
max | 0.294dB |
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Fezz Audio for the Lybra 300B compared directly against our own. The published specifications are sourced from Fezz Audio’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended from DC to 1MHz, assume, unless otherwise stated, 10W into 8 ohms and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.
Parameter | Manufacturer | SoundStage! Lab |
Rated output power into 8 ohms (10% THD) | 15W | 14.7W |
Frequency response (-3dB) | 12Hz–60kHz | 11Hz–61kHz |
THD (1W, 8 ohms) | <0.25% | 0.3% |
Our primary measurements revealed the following using the line-level analog input (unless specified, assume a 1kHz sinewave at 2Vrms, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Maximum output power into 8 ohms (10% THD+N, unweighted) | 14.7W | 15.4W |
Maximum output power into 4 ohms (10% THD+N, unweighted) | 15.0W | 15.5W |
Maximum burst output power (IHF, 8 ohms) | 15W | 15W |
Maximum burst output power (IHF, 4 ohms) | 15W | 15W |
Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |
Crosstalk, one channel driven (10kHz) | -57.5dB | -49.5dB |
Damping factor | 2.9 | 2.9 |
Clipping no-load output voltage (10% THD) | 22Vrms | 22Vrms |
DC offset | <-0.5mV | <-0.5mV |
Gain (maximum volume) | 27.9dB | 27.6dB |
IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-31dB | <-31dB |
IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-19dB | <-19dB |
Input impedance (line input, RCA) | 52.8k ohms | 52.1k ohms |
Input sensitivity (for rated power, maximum volume) | 515mVrms | 520mVrms |
Noise level (no signal, A-weighted, volume min) | <73uVrms | <71uVrms |
Noise level (no signal, 20Hz to 20kHz, volume min) | <450uVrms | <380uVrms |
Signal-to-noise ratio (15W, A-weighted, 2Vrms in) | 101.6dB | 101.2dB |
Signal-to-noise ratio (15W, 20Hz to 20kHz, 2Vrms in) | 87.0dB | 87.8dB |
Signal-to-noise ratio (15W, A-weighted, max volume) | 97.2dB | 95.9dB |
THD ratio (unweighted) | <2.77% | <2.88% |
THD+N ratio (A-weighted) | <3.17% | <3.30% |
THD+N ratio (unweighted) | <2.77% | <2.88% |
Minimum observed line AC voltage | 122VAC | 122VAC |
For the continuous dynamic power test, the Lybra 300B was able to sustain 15W into 4 ohms (~10% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (50.8W) for five seconds, for five continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the Lybra was very warm; however, this is the normal operating condition of the amplifier.
Frequency response (8-ohm loading, line-level input, relative level)
In our measured frequency response (relative to 1kHz) chart above, the blue and red plots show the speaker-level outputs (relative to 1kHz, at 10W into 8 ohms). The Lybra’s speaker outputs are near flat within the audioband (about -0.5dB at 20Hz and -0.2dB at 20kHz), and exhibit an average bandwidth (-3dB at 61kHz). The small ~0.2dB blip at around 650Hz is real, was repeatable, and was also observed with constant signals in the analyzer’s bench mode. With the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.
Phase response (line-level input)
Above is the phase response plot from 20Hz to 20kHz for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The Lybra does not invert polarity. Here we find +70 degrees at 20Hz, and -20 degrees at 20kHz.
RMS level vs. frequency vs. load impedance (1W, left channel only)
The chart above shows RMS level (relative to 0dBrA, which is 1W into 8 ohms or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. All sweeps were performed using the Lybra’s 8-ohm speaker outputs, to show the effects of load on frequency response. Here we can see significant deviations of about 4dB from 4 ohms to no load through the flat part of the audioband (100Hz to 10kHz), reaching as high as about 6.5dB at 20Hz. This is an indication of a very low damping factor, or high output impedance. The variation in RMS level when a real speaker was used is about 3.5dB through most of the audioband.
To expand on the Lybra’s frequency response when using a real speaker, the chart below . . .
. . . shows the frequency response (relative to 1kHz) using a continuous sweep for the Focal Chora 806. Again we see deviations of up to 3.5dB within the audioband. It’s important to mention that deviations of this magnitude would be clearly audible, giving the Lybra amplifier a “sound” that would change based on the characteristic impedance curve of the speaker it’s connected to.
THD ratio (unweighted) vs. frequency vs. output power
The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sinewave stimulus at the analog line-level input. The blue and red plots are for left and right channels at 0.1W output into 8 ohms, purple/green at 1W, and pink/orange at 10W. The power was varied using the volume control. At 0.1W, THD ratios hovered between from 0.2 an 0.1% from 20Hz to 20kHz. At 1W, THD ratios hovered between from 0.7 to 0.3% from 20Hz to 20kHz. At 10W, THD ratios hovered between from 5 and 2% from 20Hz to 20kHz.
THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD ratios measured at the output of the Lybra as a function of output power for the analog line-level input for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). The 8-ohm and 4-ohm data tracked closely. THD ratios started at 0.03% at 10mW, with a steady rise to 2-3% at just over 10W, then a shaper rise to 10% THD at 15W.
THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD+N ratios measured at the output of the Lybra as a function of output power for the analog line-level-input for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). The 8-ohm and 4-ohm data tracked closely. THD+N ratios started at 0.1 to 0.2% from 10mW to 200mW, followed by a steady rise to 2 to 3% at just over 10W, then a shaper rise to 10% THD at 15W.
THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)
The chart above shows THD ratios measured at the output of the Lybra as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage of 2.83Vrms that yields 1W at the output into 8 ohms using the 8-ohm speaker output, and roughly 2/4W into 4/2 ohms using the 4-ohm speaker outputs, for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find very similar THD ratios for the 8- and 4-ohm data (the 8-ohm data is about 2-3dB lower than the 4-ohm data), ranging from around 1% down to 0.3% from 20Hz to 20kHz. For the 2-ohm load, THD ratios were higher, hovering around the 2% mark through most of the audioband.
THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows THD ratios measured at the output of the Lybra as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). Both speaker THD plots showed signficant variations in THD ratios, both above and below the 0.6–0.4% line for the 8-ohm dummy load. The two-way speaker ranged from 5% THD at 20Hz to a low of 0.15% at 2–3kHz. The three-way speaker ranged from 2% at 100Hz to a low of 0.06% at 3kHz. This shows that THD ratios can vary signficanlty for the Lybra, depending on the speaker’s impedance at a given frequency.
IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows intermodulation distortion (IMD) ratios measured at the output of the Lybra as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method was used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). The results for the dummy load were fairly consistent, hovering around 0.4% throughout the sweep. We find that both speakers yielded IMD ratios that were lower (by 10dB) compared to the dummy load between 2.5kHz and 5kHz. From the 6kHz to 20kHz, IMD ratios were almost 10dB higher for the three-way speaker compared to the dummy load, while the two-way speaker yielded IMD ratios lower than the dummy load throughout the sweep.
IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows IMD ratios measured at the output of the Lybra as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method was used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are similar but still varied by as much as +5dB and -10dB relative to the constant 1.5% measured across the resistive dummy load. The lowest IMD level for the 2-way speaker was found at 80Hz at 0.3%, while the two-way speaker yielded 0.7% around 60Hz.
FFT spectrum – 1kHz (line-level input)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s second (2kHz) and third (3kHz) harmonic dominate at around -35dBrA, or 2%. The other signal harmonics are below -50dBrA, or 0.3%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 60Hz peak dominating at -90dBrA, or 0.003%.
FFT spectrum – 50Hz (line-level input)
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s second (2kHz) and third (3kHz) harmonic dominate at around -35dBrA, or 2%. The other signal harmonics are below -50dBrA, or 0.3%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 60Hz peak dominating at -90dBrA, or 0.003%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -45dBrA, or 0.6%. The third-order modulation products, at 17kHz and 20kHz, are at around the same level.
Intermodulation distortion FFT (line-level input, APx 32 tone)
Shown above is the FFT of the speaker-level output of the Lybra with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the "grass" between the test tones—are distortion products from the amplifier that are below the -70dBrA, or 0.03%, level.
Square-wave response (10kHz)
Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the Lybra’s slew-rate performance. Rather, it should be seen as a qualitative representation of the Lybra’s average bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (e.g., 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. Here we can see an average squarewave reproduction, with some softening and over/under-shoot in the corners.
Damping factor vs. frequency (20Hz to 20kHz)
The graph above is the damping factor as a function of frequency with an 8-ohm load connected to the 8-ohm speaker output. Both channels track closely, with a very low damping factor of between 2 (20Hz) and 3 (100Hz to 20kHz). This very high output impedance (2.67 ohms at 1kHz) explains the significant variations measured in frequency response with a real speaker load.
The graph above is the damping factor as a function of frequency with a 4-ohm load connected to the 4-ohm speaker output. It is effectively identical to the 8-ohm damping factor graph. Since damping factor is defined as the ratio of the refrence load impedance over the output impedance, this means that the output impedance on the 4-ohm tap is half that of the output impedance on the 8-ohm tap.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Roger Kanno on SoundStage! Hi-Fi on October 1, 2023
General Information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The NuPrime Evolution Two was conditioned for one hour at 1/8th full rated power (~35W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.
The Evolution Two is a monoblock (i.e., single channel) amplifier with one unbalanced (RCA) and one balanced (XLR) input, and one speaker-level output. 400mVrms was required at the input to achieve the reference 10W into 8 ohms. For the purposes of these measurements, unless otherwise specified, the balanced input was used.
Because the Evolution Two uses a digital amplifier technology that exhibits considerable noise above 20kHz (see FFTs below), our typical input bandwidth filter setting of 10Hz–90kHz for frequency sweeps was necessarily changed to 10Hz–22.4kHz, and limited to 6kHz to adequately capture the second and third signal harmonics with the restricted-bandwidth setting.
Published specifications vs. our primary measurements
The table below summarizes the measurements published by NuPrime for the Evolution Two compared directly against our own. The published specifications are sourced from NuPrime’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended from DC to 1MHz, assume, unless otherwise stated, 10W into 8 ohms and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channesl.
Parameter | Manufacturer | SoundStage! Lab |
Rated output power into 8 ohms (1% THD, 1kHz) | 300W | 294W |
Rated output power into 4 ohms (1% THD, 1kHz) | 620W | 381W* |
Power output (peak, IHF, 8 ohms) | 410W | 463W |
Power output (peak, IHF, 4 ohms) | 840W | 811W |
Gain (unbalanced) | x21 | x22 |
Sensitivity to rated power (balanced) | 2.1Vrms | 2.1Vrms |
Input impedance (unbalanced) | 47k ohms | 27.0k ohms |
THD (5W, 8 ohms) | 0.003% | 0.0034% |
THD (50W, 8 ohms) | 0.006% | 0.0065% |
THD (100W, 8 ohms) | 0.006% | 0.0078% |
SNR (5W, 20Hz -20kHz bandwidth, 8 ohms) | 95dB | 98.4dB |
SNR (50W, 20Hz -20kHz bandwidth, 8 ohms) | 105dB | 108.6dB |
SNR (100W, 20Hz -20kHz bandwidth, 8 ohms) | 108dB | 111.6dB |
* protection circuit engages after a few seconds at THD = 0.04%
Our primary measurements revealed the following using the Line 2 unbalanced analog input (unless specified, assume a 1kHz sinewave at 400mVrms at the input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):
Parameter | Mono channel |
Maximum output power into 8 ohms (1% THD+N, unweighted) | 294W |
Maximum output power into 4 ohms (1% THD+N, unweighted) | *381W |
Maximum burst output power (IHF, 8 ohms) | 463W |
Maximum burst output power (IHF, 4 ohms) | 811W |
Continuous dynamic power test (5 minutes) | passed |
Damping factor | 496 |
Clipping no-load output voltage (instantaneous power into 8 ohms) | 49.8Vrms |
DC offset | <4.7mV |
Gain (maximum volume) | 27.25dB |
IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-66dB |
IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-79dB |
Input sensitivity (for full power) | 2.1Vrms |
Input impedance (balanced) | 10.7k ohms |
Input impedance (unbalanced) | 27.0k ohms |
Noise level (with signal, A-weighted) | <56uVrms |
Noise level (with signal, 20Hz to 20kHz) | <77uVrms |
Noise level (no signal, A-weighted) | <56uVrms |
Noise level (no signal, 20Hz to 20kHz) | <77uVrms |
Signal-to-noise ratio (294W, A-weighted) | 118.9dB |
Signal-to-noise ratio (294W, 20Hz to 20kHz) | 116.1dB |
THD ratio (unweighted) | <0.0044% |
THD+N ratio (A-weighted) | <0.0051% |
THD+N ratio (unweighted) | <0.0046% |
Minimum observed line AC voltage | 121VAC |
* protection circuit engages after a few seconds at THD = 0.04%
For the continuous dynamic power test, the Evolution Two was able to sustain about 630W into 4 ohms (~1% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (63W) for five seconds, for five continuous minutes. However, during the test, the initiation of a protection circuit did occur several times. The protection circuit engages and disengages very quickly, allowing the Evolution Two to run through the test mostly uninterrupted. Therefore, we are calling a conditional pass on this test. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the Evolution Two was cool to the touch. Note that the Evolution Two is not able to sustain 630W into 4 ohms continuously for more than about one second before a protection circuit is triggered.
Frequency response (8-ohm loading, line-level input, relative level)
In our frequency-response plot above, measured across the speaker outputs at 10W into 8 ohms, the Evolution Two exhibits a clear rise at high frequencies. We have confirmed with NuPrime that this is intentional and not due to a defective unit. At low frequencies, the Evolution Two is essentially flat down to 5Hz. The rise at high frequencies was measured at about 0.6dB at 10kHz and 2dB at 20kHz. The rise peaks around 80–90kHz, at +6.5dB. Whether or not this deviation from a flat response would be audible would depend on the speakers used, musical content, and most importantly, the age of the listener. The -2dB point is at 200kHz, which is the maximum allowable frequency using the AP analyzer.
Phase response (8-ohm loading)
Above is the phase response plot from 20Hz to 20kHz for the balanced line-level input, measured across the speaker outputs at 10W into 8 ohms. The Evolution Two does not invert polarity and exhibits, at worst, about +5 degrees of phase shift within the audioband between 10kHz and 20kHz.
RMS level vs. frequency vs. load impedance (1W, left channel only)
The chart above shows RMS level (relative to 0dBrA, which is 1W into 8 ohms or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .
. . . is the same but zoomed in to highlight differences. Here we find the maximum deviation between an 8-ohm load and no load to be around 0.08dB. This is an indication of a very high damping factor, or low output impedance. With a real speaker, the deviations are much lower, at about 0.02dB between 20Hz and 1kHz.
THD ratio (unweighted) vs. frequency vs. output power
The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sinewave stimulus at the analog line-level input. The blue plot is at 1W output into 8 ohms, purple at 10W, and pink at 265W. The 1W data yielded fairly constant THD figures, at 0.003% from 20Hz to 3kHz, then a rise to 0.01% at 6kHz. At 10W, THD data ranged from 0.001% from 20Hz to 100Hz, then a steady rise to 0.03% at 6kHz. At 265W, THD data ranged from 0.002% from 20Hz to 100Hz, then a steady rise to 0.1% at 6kHz.
THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD ratios measured at the output of the Evolution Two as a function of output power for the analog line-level input for an 8-ohm load (blue) and a 4-ohm load (purple). The 8-ohm data ranged from about 0.1% to 0.05% from 50 to 400mW, then a dip down to 0.003% to 0.005% from 500mW to 20W, a rise to 0.03% at the “knee” at just shy of 300W, then reaching the 1% THD mark at roughly 350W. Please note that each measurement in this sweep is only two seconds long, and by contrast, we were not able to sustain more than 294W into 8 ohms continuously. The 4-ohm data ranged from about 0.1% from 50 to 100mW, then a dip down to 0.003% to 0.01% from 150mW to 100W, a rise to 0.03% at the “knee” at 300W, then the Evolution Two protection circuit was triggered, precluding the collection of reliable data points above 300W.
THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD+N ratios measured at the output of the Evolution Two as a function of output power for the analog line-level input, for an 8-ohm load (blue) and a 4-ohm load (purple). The 8-ohm data ranged from about 0.1% to 0.05% from 50 to 400mW, then a dip down to 0.005% from 500mW to 20W, a rise to 0.05% at the “knee” at just shy of 300W, then reaching the 1% THD mark at roughly 350W. Please note that each measurement in this sweep is only two seconds long, and by contrast, we were not able to sustain more than 294W into 8 ohms continuously. The 4-ohm data ranged from about 2% from 50 to 100mW, then a dip down to 0.01% from 150mW to 100W, a rise to 0.03% at the “knee” at 300W, then the Evolution Two protection circuit was triggered, precluding the collection of reliable data points above 300W.
THD ratio (unweighted) vs. frequency vs. load
The chart above shows THD ratios measured at the output of the Evolution Two as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields roughly 30W at the output into 8 ohms (blue), 60W into 4 ohms (purple), and 120W into 2 ohms (pink). The 8-ohm data ranged from 0.001% from 20Hz to 100Hz, then a steady rise to 0.03% at 6kHz. The 4-ohm THD data were only about 5dB higher compared to the 8-ohm data, but converging at the same 0.03% at 6kHz. The 2-ohm data were considerably higher from 20Hz to 500Hz, yielding a fairly constant 0.005% to 0.008%, then a rise to 0.06% at 6kHz. The maximum achieved continuous power into 2 ohms was about 190W, where the protection circuit engaged after about four seconds. Nevertheless, the Evolution Two proved to be stable into 2 ohms with continuous power in the 60W to 100W range.
THD ratio (unweighted) vs. frequency into 8 ohms and real speakers
The chart above shows THD ratios measured at the output of the Evolution Two as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). At very low freqencies, the two-way speaker yielded the highest THD ratios (0.02%), which is typical with many amps. From 30Hz to 500Hz, all three THD plots are very close to one another, around the 0.003% mark. From 500Hz to 6kHz, the Evolution Two yielded lower THD ratios with real speakers compared to the dummy resistive load, ranging from 0.001 to 0.002%.
IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers
The chart above shows intermodulation distortion (IMD) ratios measured at the output of the Evolution Two as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method was used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). Here the three-way speaker yielded the highest IMD results, from 0.001% to 0.02%. The dummy load was in between, while the two-way speaker yielded the lowest IMD results, between 0.0005% and 0.003%.
IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers
The chart above shows IMD ratios measured at the output of the Evolution Two as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method was used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). The resistive dummy load was fairly constant at 0.008%, while the speaker IMD results fluctuated above and below this value by as much as 10dB.
FFT spectrum – 1kHz (line-level input)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s third (3kHz) harmonic dominates at -90dBrA, or 0.003%. The second, fourth, and fifth harmonics are a little lower, around -100dBrA, or 0.001%. Power-supply-related noise peaks can be seen but at low levels: -120dBrA, or 0.0001%, and below.
FFT spectrum – 50Hz (line-level input)
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most dominant (non-signal) peaks are the second (100Hz) and third (150Hz) signal harmonics at roughly -100dBrA, or 0.001%. Power-supply-related noise peaks can be seen but at low levels: -120dBrA, or 0.0001%, and below.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -100dBrA, or 0.001%, and the third-order modulation products, at 17kHz and 20kHz, are higher at below -75dBrA, or 0.02%.
Intermodulation distortion FFT (line-level input, APx 32 tone)
Shown above is the FFT of the speaker-level output of the Evolution Two with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the "grass" between the test tones—are distortion products from the amplifier and are below the -100dBrA, or 0.001%, level. Higher-amplitude distortion products are seen at higher frequencies.
Square-wave response (10kHz)
Above is the 10kHz squarewave response using the balanced analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the Evolution Two’s slew-rate performance. Rather, it should be seen as a qualitative representation of the Evolution Two’s mid-tier bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (e.g., 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. In the case of the Evolution Two, however, what dominates the plateaus of the squarewave in the top graph is a 600kHz sinewave, the frequency at which the switching oscillator in the class-D amp is operating (see FFT below).
Square-wave response (10Hz–250kHz bandwidth)
Above is the 10kHz squarewave response using the analog input, at roughly 10W into 8 ohms, with a 250kHz restricted bandwidth to remove the modulation from the 600kHz oscillator. Here we find a squarewave with significant over-shoot in the corners, likely due to the Evolution Two’s rise in frequency response at high frequencies.
FFT spectrum of 400kHz switching frequency relative to a 1kHz tone
The Evolution Two’s amplifier relies on a switching oscillator to convert the input signal to a pulse-width-modulated (PWM) squarewave (on/off) signal before sending the signal through a low-pass filter to generate an output signal. The Evolution TWo oscillator switches at a rate of about 600kHz, and this graph plots a wide bandwidth FFT spectrum of the amplifier’s output at 10W into 8 ohms as it’s fed a 1kHz sinewave. We can see that the 600kHz peak is quite evident, and at -30dBrA. There is also a peak at 1.2MHz (the second harmonic of the 600kHz peak), at -75dBrA. Those two peaks—the fundamental and its second harmonics—are direct results of the switching oscillators in the Evolution Two amp module. The noise around those very-high-frequency signals are in the signal, but all that noise is far above the audioband—and therefore inaudible—and so high in frequency that any loudspeaker the amplifier is driving should filter it all out anyway.
Damping factor vs. frequency (20Hz to 20kHz)
The final graph above is the damping factor as a function of frequency. We find very high damping factor values, from 500 up to over 1000 at higher frequencies. We were unable to reliably measure damping factor above around 6–7kHz, where we actually measured negative output impedances. This is impossible, and we can only speculate as to what the amplifier is doing. Based on the measurements, it seems as though the Evolution Two increases gain slightly into small loads at high frequencies.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Matt Bonaccio on SoundStage! Hi-Fi on September 1, 2023
General Information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The Ars-Sonum Armonía was conditioned for one hour at 1/8th full rated power (~3.5W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.
The Armonía has two sets of unbalanced inputs (RCA) and a pair of speaker-level outputs. A level of 360mVrms was required at the input to achieve the reference 10W into 8 ohms for the Line 2 input, which we measured yielding a typical gain of about 28dB. The Line 1 input offers more gain—we measured about 34dB. For the purposes of these measurements, unless otherwise specified, Line 2 was used.
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Ars-Sonum for the Armonía compared directly against our own. The published specifications are sourced from Ars-Sonum’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended from DC to 1MHz, assume, unless otherwise stated, 10W into 8 ohms and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.
Parameter | Manufacturer | SoundStage! Lab |
Rated output power into 8 ohms (1% THD, 1kHz) | 30W | 24W |
SNR (A-weighted, 8 ohms, full rated power) | >90dB | 92.1dB |
THD (1kHz, 20W, 8 ohms) | <0.4% | <0.45% (0.21% left) |
Frequency response (-3dB) | 5Hz-30kHz | 5.6Hz-55.8kHz |
Our primary measurements revealed the following using the Line 2 unbalanced analog input (unless specified, assume a 1kHz sinewave at 360mVrms at the input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Maximum output power into 8 ohms (1% THD+N, unweighted) | 24W | 24W |
Maximum output power into 4 ohms (1% THD+N, unweighted) | 11W | 11W |
Maximum burst output power (IHF, 8 ohms) | 30.6W | 30.6W |
Maximum burst output power (IHF, 4 ohms) | 29.5W | 29.5W |
Continuous dynamic power test (five minutes, both channels driven) | passed | passed |
Crosstalk, one channel driven (10kHz) | -50.0dB | -60.5dB |
Damping factor | 3.4 | 6.9 |
DC offset | <-0.3mV | <-0.3mV |
Gain (Line 2) | 28.0dB | 28.3dB |
Gain (LIne 1) | 33.6dB | 33.8dB |
IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-67dB | <-55dB |
IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-50dB | <-47dB |
Input impedance (line input) | 112k ohms | 110k ohms |
Input sensitivity (for full power, 24W) | 620mVrms | 600mVrms |
Noise level (with signal, A-weighted) | <380uVrms | <340uVrms |
Noise level (with signal, 20Hz to 20kHz) | <1110uVrms | <1020uVrms |
Noise level (no signal, A-weighted) | <340uVrms | <350uVrms |
Noise level (no signal, 20Hz to 20kHz) | <1080uVrms | <1090uVrms |
Signal-to-noise ratio (24W, A-weighted) | 92.2dB | 92.1dB |
Signal-to-noise ratio (24W, 20Hz to 20kHz) | 82.1dB | 82.3dB |
THD ratio (unweighted) | <0.054% | <0.122% |
THD+N ratio (A-weighted) | <0.059% | <0.139% |
THD+N ratio (unweighted) | <0.056% | <0.122% |
Minimum observed line AC voltage | 124VAC | 124VAC |
For the continuous dynamic power test, the Armonía was able to sustain 20W into 4 ohms (~5% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (2W) for five seconds, for five continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the Armonía was very hot to the touch, which is the same as its heat output when powered on with no signal.
Frequency response (8-ohm loading)
In our frequency-response plots above, measured across the speaker outputs at 10W into 8 ohms, the Armonía is near flat within the audioband (-0.5/-0.4dB, 20Hz/20kHz). The -3dB points are at about 5.5Hz and 56kHz. There is also a rise in the response at around 8Hz—nearly 1dB. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.
Phase response (8-ohm loading)
Above are the phase response plots from 20Hz to 20kHz for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The Armonía does not invert polarity and exhibits, at worst, about +/-20 degrees (at 20Hz/20kHz) of phase shift within the audioband.
RMS level vs. frequency vs. load impedance (1W, left channel only)
The chart above shows RMS level (relative to 0dBrA, which is 1W into 8 ohms or 2.83Vrms) as a function of frequency for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the cyan plot is an actual speaker (Focal Chora 806, measurements can be found here). As per the manufacturer, we avoided applying a signal to the Armonía with no load connected. The chart below . . .
. . . is the same but zoomed in to highlight differences. Here we find the maximum deviation between an 8-ohm and 4-ohm load to be around 1.4dB. This is an indication of a very low damping factor, or high output impedance. With a real speaker, the deviations are worse—as much as 3dB (which would be clearly audible) between 200Hz and 1.5kHz.
THD ratio (unweighted) vs. frequency vs. output power
The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sinewave stimulus at the analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 24W. The 1W data yielded the lowest THD figures, from 0.4% (left) at 20Hz, down to 0.02% from 200Hz to 3kHz, then up to 0.1% at 20kHz. The right channel had a flatter response, but consistently yielded higher THD figures (5dB) from 200Hz to 3kHz at all power levels. At 10W, THD data for the left channel ranged from 0.5%, down to 0.05%, then up to 0.3%. At 24W, THD data were flatter, around 1 to 3%.
THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD ratios measured at the output of the Armonía as a function of output power for the analog line level-input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). The 8-ohm data ranged from about 0.02% from 10 to 300mW, then a steady climb to 0.3/0.5% (left/right at 20W), reaching the 1% THD mark around 24W. The 4-ohm data ranged from about 0.02% from 10 to 200mW, then a steady climb to 0.5/1% (left/right at 10W), reaching the 1% THD mark jut past 11W, and the 5% THD mark just shy of 20W. Again here, the left channel yielded lower THD ratios (5-10dB) compared to the right channel through the most-likely-used power band of the amplifier (1W to 10W).
THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD+N ratios measured at the output of the Armonía as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). THD+N values for the 8-ohm data ranged from 0.4% at 10mW down to just 0.04% (left channel) at 2-5W. The 4-ohm data yielded similar THD+N values up to about 300mW, then higher values (10dB) then the 8-ohm data due to the higher THD.
THD ratio (unweighted) vs. frequency at 8 and 4 ohms
The chart above shows THD ratios measured at the output of the Armonía as a function of frequency into two different loads (8/4 ohms) for a constant input voltage that yields 10W at the output into 8 ohms. As per the manufactuerer, we avoided applying a signal to the Armonía with a 2-ohm load connected, which we would normally do. The 8-ohm load data are the blue/red traces and the 4-ohm load are the purple/green traces. The 8-ohm THD data for the left channel ranged from 0.5%, down to 0.05%, then up to 0.3%, with the right channel yielding higher THD ratios (5-10dB) from 200Hz to 3kHz. The 4-ohm THD data were much higher, between 1 and 2% from 20Hz to 20kHz.
THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows THD ratios measured at the output of the Armonía as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). There are significant varations in THD ratios between the resisitve dummy load and real speakers. The two-way speaker yielded the largest swings, from 4% at 20Hz, down to 0.007% at 2kHz. This is likely due to the Armonía’s low damping factor, and just like with frequency repsonse, shows that THD results will vary greatly depending on the speaker connected to it.
IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows intermodulation distortion (IMD) ratios measured at the output of the Armonía as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method was used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). Here the three-way speaker yielded the highest IMD results, from 0.05% to 0.1%. The dummy load and two-way speaker were as low as 0.01-0.02%.
IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows IMD ratios measured at the output of the Armonía as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method was used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). The resistive dummy load was fairly constant at 0.06-0.08%, with the speaker IMD results fluctuating above and below these values by as much as 10dB.
FFT spectrum – 1kHz (line-level input)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s second (2kHz) and fifth (5kHz) harmonic dominate, as high as -60dBrA (right channel), or 0.1%. Overall, the right channel yielded higher signal harmonic related peaks, but not always. At 3kHz, the right channel dominates at -70dBrA, or 0.03%, while at 4kHz, the left channel dominates at -80dBRa, or 0.01%. Power-supply-related noise peaks are pervasive, with the fundamental (60Hz) and second (120Hz) harmonics dominating between -80 and -90dBrA, or 0.01% and 0.003%.
FFT spectrum – 50Hz (line-level input)
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most dominant (non-signal) peaks are the second (100Hz) and third (150Hz) signal harmonics at roughly -60dBrA, or 0.1%. Power-supply-related harmonics can be seen here at the fundamental (60Hz) and second harmonic (120Hz) at -80dBrA, or 0.01%, as well as multiples and resulting IMD products at lower levels.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -80/-60dBrA (left/right), or 0.01/0.1%, and the third-order modulation products, at 17kHz and 20kHz, are slightly below -80/-70dBrA (left/right), or 0.01/0.03%.
Intermodulation distortion FFT (line-level input, APx 32 tone)
Shown above is the FFT of the speaker-level output of the Armonía with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the "grass" between the test tones—are distortion products from the amplifier and are below the -70dBrA, or 0.03%, level.
Square-wave response (10kHz)
Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the Armonía’s slew-rate performance. Rather, it should be seen as a qualitative representation of the Armonía’s mid-tier bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (e.g., 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. In the case of the Armonía however, we see a relatively clean squarewave reproduction, although with softened cornered, but no over/undershoot.
Damping factor vs. frequency (20Hz to 20kHz)
The final graph above is the damping factor as a function of frequency. We find poor damping factor values, characteristic of tube amplifiers. The right channel was higher, hovering between 6 and 8, while the left channel yielded a fairly constant 3.4 from 30Hz to 20kHz.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Philip Beaudette on SoundStage! Hi-Fi on August 1, 2023
General Information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The Hegel H600 was conditioned for 1 hour at 1/8th full rated power (~37W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.
The H600 offers two unbalanced (RCA) and two balanced (XLR) line-level analog inputs, seven digital inputs (one BNC, one RCA, three optical, one ethernet, and on USB), two pairs of line-level outputs (fixed and variable over RCA), and two pairs of speaker-level outputs (left and right). For the purposes of these measurements, the following inputs were evaluated: RCA digital coaxial, and the analog line-level balanced inputs (a 1kHz FFT using the unbalanced inputs is also provided).
Most measurements were made with a 2Vrms line-level analog input or a 0dBFS digital input. The signal-to-noise ratio (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 300W (8 ohms). For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum, but with a lower input voltage to achieve the same 300W output.
Based on the accuracy and non-repeatable results at various volume levels of the left/right channel matching (see table below), the H600 volume control is likely digitally controlled but operating in the analog domain. The volume control offers a total range from -62.3dB to +32.8dB between the line-level balanced analog inputs and the speaker outputs. Volume step sizes varied, from 5 to 2dB for the first nine steps, then 1dB from levels 10 to 55, then 0.5dB steps from 56 to 100.
The analyzer’s input bandwidth filter was set to 10Hz–22.4kHz for all measurements, except for frequency response (DC to 1 MHz), FFTs (10Hz to 90kHz), and THD vs. frequency (10Hz to 90kHz). The latter to capture the second and third harmonics of the 20kHz output signal. Since the H600 is a conventional class-AB amp, there was no issue with excessive noise above 20kHz.
Volume-control accuracy (measured at speaker outputs): left-right channel tracking
Volume position | Channel deviation |
1 | 0.04dB |
20 | 0.024dB |
30 | 0.025dB |
40 | 0.024dB |
50 | 0.034dB |
60 | 0.032dB |
70 | 0.029dB |
80 | 0.026dB |
90 | 0.022dB |
100 | 0.023dB |
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Hegel for the H600 compared directly against our own. The published specifications are sourced from Hegel’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended from DC to 1MHz, assume, unless otherwise stated, 10W into 8 ohms and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.
Parameter | Manufacturer | SoundStage! Lab |
Rated output power into 8 ohms (1% THD) | 303W | 313W |
Frequency response (5Hz - 100kHz) | 5Hz to 180kHz | 5Hz-180kHz (-1.3/+0.1dB) |
SNR (A-weighted, rated output) | >100dB | 114dB |
Crosstalk (1kHz) | <-100dB | -103/-98dB (L/R) |
Distortion (50W/8ohm/1kHz) | <0.005% | <0.0023% |
Intermodulation distortion (19kHz + 20kHz) | >0.01% | 0.0085% |
Damping factor (1kHz) | *4000 | 516 |
* Hegel measures damping factor directly at the output stage whereas we measure at the output terminals.
Our primary measurements revealed the following using the line-level analog input and digital coaxial input (unless specified, assume a 1kHz sinewave at 2Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Maximum output power into 8 ohms (1% THD+N, unweighted) | 313W | 313W |
Maximum output power into 4 ohms (1% THD+N, unweighted) | 519W | 519W |
Maximum burst output power (IHF, 8 ohms) | 322.0W | 322.0W |
Maximum burst output power (IHF, 4 ohms) | 626.6W | 626.6W |
Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |
Crosstalk, one channel driven (10kHz) | -104.6dB | -97.5dB |
Damping factor | 516 | 530 |
Clipping no-load output voltage | 52.2Vrms | 52.2Vrms |
DC offset | <-0.7mV | <1mV |
Gain (pre-out) | 5.26dB | 5.28dB |
Gain (maximum volume) | 32.83dB | 32.86dB |
IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-82dB | <-81dB |
IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-79dB | <-79dB |
Input impedance (line input, XLR) | 11.4k ohms | 11.4k ohms |
Input impedance (line input, RCA) | 12.9k ohms | 12.8k ohms |
Input sensitivity (for rated power, maximum volume) | 1.12Vrms | 1.12Vrms |
Noise level (with signal, A-weighted) | <57uVrms | <55uVrms |
Noise level (with signal, 20Hz to 20kHz) | <73uVrms | <78uVrms |
Noise level (no signal, A-weighted, volume min) | <53uVrms | <50uVrms |
Noise level (no signal, 20Hz to 20kHz, volume min) | <64uVrms | <61uVrms |
Output impedance (pre-out) | 1004 ohms | 1002 ohms |
Signal-to-noise ratio (300W, A-weighted, 2Vrms in) | 114.7dB | 113.8dB |
Signal-to-noise ratio (300W, 20Hz to 20kHz, 2Vrms in) | 112.1dB | 110.1dB |
Signal-to-noise ratio (300W, A-weighted, max volume) | 111.7dB | 110.3dB |
Dynamic range (300W, A-weighted, digital 24/96) | 109.9dB | 109.8dB |
Dynamic range (300W A-weighted, digital 16/44.1) | 95.7dB | 95.6dB |
THD ratio (unweighted) | <0.0027% | <0.0022% |
THD ratio (unweighted, digital 24/96) | <0.0028% | <0.0022% |
THD ratio (unweighted, digital 16/44.1) | <0.0028% | <0.0022% |
THD+N ratio (A-weighted) | <0.0031% | <0.0025% |
THD+N ratio (A-weighted, digital 24/96) | <0.0032% | <0.0026% |
THD+N ratio (A-weighted, digital 16/44.1) | <0.0036% | <0.0031% |
THD+N ratio (unweighted) | <0.0028% | <0.0023% |
Minimum observed line AC voltage | 122VAC | 122VAC |
For the continuous dynamic power test, the H600 was able to sustain 520W into 4 ohms (~2% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (52W) for 5 seconds, for 5 continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the H600 was hot enough to the touch to cause pain after a few seconds.
Frequency response (8-ohm loading, line-level input)
In our measured frequency-response chart above, the blue and red plots show the speaker-level outputs (relative to 1kHz, at 10W into 8 ohms). The H600’s speaker outputs are near flat within the audioband (-0.15dB at 20Hz, 0dB at 20kHz), and show a very extended bandwidth (0dB at 80kHz). The H600 appears to be AC-coupled, due the attenuation in response below 20Hz. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.
Phase response (8-ohm loading, line-level input)
Above is the phase response plot from 20Hz to 20kHz for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The H600 does not invert polarity. Here we find essentially no phase shift at 20kHz, and 10 degrees at 20Hz, owing to the H600’s extended bandwidth and AC-coupled design.
Frequency response vs. input type (8-ohm loading, left channel only)
The chart above shows the H600’s frequency response (relative to 1kHz) as a function of input type measured across the speaker outputs at 10W into 8 ohms. The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 10Hz to 22kHz using the coaxial digital input, and the purple trace is for a 24/96 dithered digital input signal from 10Hz to 48kHz, while the pink trace is for a 24/192 dithered digital input signal from 10Hz to 96kHz. The green trace is the same analog input frequency response seen above. All three digital responses show a rise in output above 20kHz, with the 16/44.1 data peaking at +0.15dB at 19.2kHz, the 24/96 data peaking at +0.72dB at 43.3kHz, and the 24/192 data peaking at +1.8dB at 78.3kHz. All three digital responses exhibit brick-wall-type filtering, with -3dB points at 21.2kHz (16/44.1), 46.8kHz (24/96), and 93.8kHz (24/192).
Digital linearity (16/44.1 and 24/96 data)
The chart above shows the results of a linearity test for the coaxial digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the fixed line-level outputs of the H600 for a 2.4Vrms (at 0dBFS) output signal. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response would be a straight flat line at 0dB. Both data were essentially perfect as of -100dBFS down to 0dBFS. At -120dBFS, the 16/44.1 data were about +2dB (left/right) above reference, while the 24/96 data were just below +1dB above reference.
Impulse response (24/44.1 data)
The graph above shows the impulse response for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s) for one sample period then back to digital silence, measured at the fixed line-level outputs of the H600. We can see that the H600 DAC utilizes a reconstruction filter with no pre-ringing.
J-Test (coaxial)
The chart above shows the results of the J-Test test for the coaxial digital input measured at the line-level pre-outs of the H600. J-Test was developed by Julian Dunn in the 1990s. It is a test signal—specifically a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (i.e., 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sinewave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (e.g., 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA and below. The test file can also be used in conjunction with artificially injected sinewave jitter by the Audio Precision, to show how well the DAC rejects jitter.
The coaxial input exhibits some low-level peaks below 1kHz, between -120 and -140dBrA. This is a relatively strong J-test result, indicating that the H600 DAC should be adequate at rejecting jitter.
J-Test (optical)
The chart above shows the results of the J-Test test for the optical digital input measured at the fixed line-level pre-outs of the H600. The optical input produced essentially the same result as with the coax input.
J-Test with 100ns of injected jitter (coaxial)
Both the coaxial and optical inputs were also tested for jitter immunity by injecting artificial sinewave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved strong. Although sidebands were visible at the 100ns jitter level, they did not exceed -135dBrA in amplitude. The optical input jitter result was very similar to the coaxial input result.
J-Test with 300ns of injected jitter (coaxial)
Both the coaxial and optical inputs were also tested for jitter immunity by injecting artificial sinewave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity again proved to be solid but not perfect, with visible sidebands at a very low -125dBrA at the 300ns jitter level. The H600 DAC did lose sync with the signal when jitter was increased beyond approximately 400ns. The optical input jitter result was very similar to the coaxial input result.
Wideband FFT spectrum of white noise and 19.1kHz sine-wave tone (coaxial input)
The plot above shows a fast Fourier transform (FFT) of the H600’s line-level pre-outs with white noise at -4 dBFS (blue/red), and a 19.1 kHz sinewave at 0dBFS fed to the coaxial digital input, sampled at 16/44.1. The medium roll-off above 20kHz in the white-noise spectrum shows the implementation of a typical brickwall-type reconstruction filter. There are no clear aliased image peaks in the audioband above the -135dBrA noise floor. Some very low frequency peaks can be seen in the FFT, however; these are at 60/120Hz due to power-supply noise. The main 25kHz alias peak is highly suppressed at -110dBrA. The second, third, and fourth distortion harmonics (38.2, 57.3, 76.4kHz) of the 19.1kHz tone are below -100dBrA.
RMS level vs. frequency vs. load impedance (1W, left channel only)
The chart above shows RMS level (relative to 0dBrA, which is 1W into 8ohms or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .
. . . is the same but zoomed in to highlight differences. Here we can see only minor deviations of about 0.04dB from 4 ohms to no load through most of the audioband, reaching as high as 0.08dB at 20kHz. This is an indication of a very high damping factor, or low output impedance. The variations in RMS level when a real speaker was used are smaller, deviating by at worst 0.04dB through most of the audioband.
THD ratio (unweighted) vs. frequency vs. output power
The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sinewave stimulus at the analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 240W. The power was varied using the volume control. At 1W and 10W, THD ratios ranged from 0.006% at 20Hz, down to 0.003% from 100Hz to 4kHz, then up to 0.01% at 20kHz. The 240W THD values were slightly higher and ranged from 0.004% at 20Hz through to about 1kHz, then up to 0.04% at 20kHz.
THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD ratios measured at the output of the H600 as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). The 8-ohm and 4-ohm data track closely and are relatively constant below the “knees,” at 0.002 to 0.005%, with the 8-ohm data outperforming the 4-ohm THD data by only 4-5dB. The “knee” for the 8-ohm data is just past 250W, then up to the 1% THD mark at 313W. With a 4-ohm load, the “knee” occurs at about 400W, and the 1% THD value was reached at 519W.
THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD+N ratios measured at the output of the H600 as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Overall, THD+N values for both loads were similar, ranging from about 0.02-0.03%, down to just above 0.003% (8-ohm). The 4-ohm THD+N ratios were a few dB worse than the 8-ohm ratios through most of the sweep.
THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)
The chart above shows THD ratios measured at the output of the H600 as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yielded 40W at the output into 8 ohms (and roughly 80W into 4 ohms, and 160W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find a roughly 3-4dB increase between the 8- and 4-ohm data, then another 5-7dB increase from 4 to 2 ohms. We find the 8-ohm trace ranging from 0.003% from 60Hz up to 4kHz, then up to 0.007% at 20kHz. These data show that the H600 is not only stable into 2-ohm loads, but will perform well in terms of THD, comparable to an 8- and 4-ohm load.
THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows THD ratios measured at the output of the H600 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). Overall, THD ratios were mostly within 5-10dB of the 8-ohm THD data, sometimes above, sometimes below. The worst-case result was at 20Hz with the two-way speaker, where THD ratios reached 0.03%. By and large, THD ratios ranged from 0.01 to 0.001%. This shows once again, that the H600 will yield consistent and stable THD results into different loads.
IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows intermodulation distortion (IMD) ratios measured at the output of the H600 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method was used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). The results for the dummy load were fairly consistent, hovering between 0.005 and 0.01% throughout the sweep. We find that the two-way speaker yielded IMD ratios 2-10dB lower than the dummy load, whereas the 3-way speaker yielded IMD ratios roughly 5dB lower than the dummy load at lower frequences, and 5dB higher at higher frequencies.
IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows IMD ratios measured at the output of the H600 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method was used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are similar, at around the 0.01% level.
FFT spectrum – 1kHz (balanced line-level input)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the balanced analog line-level input. We see that the signal’s second (2kHz) and third harmonic (3kHz) dominate at near -90dBrA, or 0.003%. The other signal harmonics are around or below -110dBrA, or 0.0003%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 60/180/300Hz peaks dominating at near -110dBrA or 0.0003%.
FFT spectrum – 1kHz (unbalanced line-level input)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the unbalanced analog line-level input. While the signal’s second (2kHz) and third harmonics (3kHz) are nearly identical to the balanced input FFT above, this FFT shows more higher odd-order signal harmonics, all the way out to 100kHz at -120dBrA, or 0.0001%, and below. The power-supply-related noise peaks are very similar to the balanced input FFT above.
FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 16/44.1. The signal and noise-related harmonics are very similar to the balanced analog input FFT above, but with a slightly elevated noise floor due to the limitations of the 16-bit word depth.
FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 24/96. The signal and noise-related harmonics are very similar to the balanced analog input FFT above.
FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)
Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and non-existent signal harmonics. Power-supply-related noise peaks can be seen at the fundamental (60Hz) and higher harmonics, at -110dBrA, or 0.0003%, and below.
FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)
Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and non-existent signal harmonics. Power-supply-related noise peaks can be seen at the fundamental (60Hz) and higher harmonics, at -110dBrA, or 0.0003%, and below.
FFT spectrum – 50Hz (line-level input)
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s third harmonic (150Hz) dominates at around -90dBrA, or 0.003%. The second signal harmonic (100Hz), and subsequent signal harmonic peaks, are at or below -100dBrA, or 0.001%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 200Hz peak dominating at -110dBrA (left), or 0.0003%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -100dBrA, or 0.001%. The third-order modulation products, at 17kHz and 20kHz, are higher at almost -90dBrA, or 0.003%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 16/44.1)
Shown above is an FFT of the intermodulation (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 16/44.1. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -100dBrA, or 0.001%. The third-order modulation products, at 17kHz and 20kHz, are higher at almost -90dBrA, or 0.003%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 24/96)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 24/96. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -100dBrA, or 0.001%. The third-order modulation products, at 17kHz and 20kHz, are higher at almost -90dBrA, or 0.003%.
Intermodulation distortion FFT (line-level input, APx 32 tone)
Shown above is the FFT of the speaker-level outputs of the H600 with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the "grass" between the test tones—are distortion products from the amplifier and reach between the -120 and -110dBrA, or 0.0001-0.0003%, level.
Square-wave response (10kHz)
Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the H600’s slew-rate performance. Rather, it should be seen as a qualitative representation of the H600’s extended bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (e.g., 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. Here we can see a very clean squarewave reproduction, with sharp corners, and no overshoot.
Damping factor vs. frequency (20Hz to 20kHz)
The final graph above is the damping factor as a function of frequency. Both channels track closely, with a higher damping factor (as high as 550) between 20Hz and 2kHz. Above 2kHz, we see a decline in the damping factor, as low as 220 at 20kHz.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Hans Wetzel on SoundStage! Ultra on August 1, 2023
General Information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The Luxman L-507Z (S/N G30100145A) was conditioned for one hour at 1/8th full rated power (~13W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.
The L-507Z offers three unbalanced (RCA) and two balanced (XLR) line-level analog inputs, one set of phono level unbalanced inputs (configurable for both MM and MC cartridges), one set of line-level pre-outputs (RCA), one set of line-level main-ins (RCA), and two pairs of speaker-level outputs (A and B). Also available are two headphone outputs, one unbalanced over ¼″ TRS, and one balanced over 4.4mm TRRS. For the purposes of these measurements, the following inputs were evaluated: analog line-level balanced inputs (a 1kHz FFT using the unbalanced inputs is also provided), and phono level unbalanced inputs (MM and MC).
Most measurements were made with a 2Vrms line-level, 5mVrms MM level, and 0.5mVrms MC level analog input. The signal-to-noise ratio (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 110W (8 ohms). For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum, but with a lower input voltage to achieve the same 110W output.
Based on the accuracy and non-repeatable results at various volume levels of the left/right channel matching (see table below), the L-507Z volume control is likely digitally controlled but operating in the analog domain. The volume control offers a total range from -80dB to +43.6dB between the line-level balanced analog inputs and the speaker outputs. Volume step sizes are 1dB throughout the range.
The analyzer’s input bandwidth filter was set to 10Hz–22.4kHz for all measurements, except for frequency response (DC to 1 MHz), FFTs (10Hz–90kHz), and THD vs Frequency (10Hz–90kHz). The latter to capture the second and third harmonics of the 20kHz output signal. Since the L-507Z is a conventional class AB amp, there was no issue with excessive noise above 20kHz.
Volume-control accuracy (measured at speaker outputs): left-right channel tracking
Volume position | Channel deviation |
min | 0.7dB |
-77.0 | 0.012dB |
-52.0 | 0.001dB |
-33.0 | 0.014dB |
-16.0 | 0.025dB |
-10.0 | 0.021dB |
-5.0 | 0.028dB |
-2.0 | 0.026dB |
0 | 0.024dB |
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Luxman for the L-507Z compared directly against our own. The published specifications are sourced from Luxman’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended from DC to 1MHz, assume, unless otherwise stated, 10W into 8ohms and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.
Parameter | Manufacturer | SoundStage! Lab |
Rated output power into 8 ohms (1% THD) | 110W | 135W |
Rated output power into 4 ohms (1% THD) | 220W | 222W |
Maximum tone control (bass) | ±8dB at 100Hz | ±8dB at 100Hz (relative to 10kHz) |
Maximum tone control (treble) | ±8dB at 10kHz | ±8dB at 10kHz (relative to 20Hz) |
Input sensitivity (MM) | 2.5mVrms | 3.15mVrms |
Input impedance (MM) | 47k ohms | 52.7k ohms |
Input sensitivity (MC) | 0.3mVrms | 0.42mVrms |
Input impedance (MC) | 100 ohms | 140 ohms |
Input sensitivity (Line RCA) | 180mVrms | 193mVrms |
Input impedance (Line RCA) | 47k ohms | 51.6k ohms |
Input sensitivity (Line XLR) | 180mVrms | 196mVrms |
Input impedance (Line XLR) | 79k ohms | 64.4k ohms |
Input sensitivity (Main in) | 1.05Vrms | 1.06Vrms |
Input impedance (Main in) | 47k ohms | 55.2k ohms |
Frequency response (phono) | 20Hz to 20kHz (±0.5dB) | 20Hz to 20kHz (±0.25dB) |
Frequency response (line) | 20Hz to 100kHz (-3dB) | 20Hz to 100kHz (-0.05/-4dB) |
THD (8-ohm, 1kHz, 100W) | <0.007% | <0.008% |
THD (8-ohm, 20Hz-20kHz, 100W) | <0.03% | <0.04% |
Signal-to-noise ratio (MM, rated power, A weighted) | 91dB | 89.5dB |
Signal-to-noise ratio (MC, rated power, A weighted) | 75dB | 71.5dB |
Signal-to-noise ratio (line, rated power, A weighted) | 105dB | 104.7dB |
Damping factor (1kHz) | 300 | 313 |
Our primary measurements revealed the following using the balanced line-level analog input (unless specified, assume a 1kHz sinewave at 2Vrms, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Maximum output power into 8 ohms (1% THD+N, unweighted) | 135W | 135W |
Maximum output power into 4 ohms (1% THD+N, unweighted) | 222W | 222W |
Maximum burst output power (IHF, 8 ohms) | 153.8W | 153.8W |
Maximum burst output power (IHF, 4 ohms) | 275.7W | 275.7W |
Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |
Crosstalk, one channel driven (10kHz) | -65.4dB | -75.0dB |
Damping factor | 355 | 314 |
Clipping no-load output voltage | 36.7Vrms | 36.7Vrms |
DC offset | <-1.6mV | <-0.5mV |
Gain (pre-out) | 14.7dB | 14.7dB |
Gain (maximum volume) | 43.7dB | 43.7dB |
IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-84dB | <-78dB |
IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-75dB | <-67dB |
Input impedance (line input, XLR) | 65.5k ohms | 64.4k ohms |
Input impedance (line input, RCA) | 51.2k ohms | 51.6k ohms |
Input sensitivity (for rated power, maximum volume) | 196mVrms | 196mVrms |
Noise level (with signal, A-weighted) | <152uVrms | <152uVrms |
Noise level (with signal, 20Hz to 20kHz) | <235uVrms | <215uVrms |
Noise level (no signal, A-weighted, volume min) | <22uVrms | <21uVrms |
Noise level (no signal, 20Hz to 20kHz, volume min) | <30uVrms | <28uVrms |
Output impedance (pre-out) | 692 ohms | 693 ohms |
Signal-to-noise ratio (110W, A-weighted, 2Vrms in) | 104.9dB | 104.7dB |
Signal-to-noise ratio (110W, 20Hz to 20kHz, 2Vrms in) | 102.5dB | 102.6dB |
Signal-to-noise ratio (110W, A-weighted, max volume) | 91.3dB | 91.5dB |
THD ratio (unweighted) | <0.0059% | <0.0165% |
THD+N ratio (A-weighted) | <0.0064% | <0.018% |
THD+N ratio (unweighted) | <0.0066% | <0.017% |
Minimum observed line AC voltage | 122 VAC | 122 VAC |
For the continuous dynamic power test, the L-507Z was able to sustain 228W into 4 ohms (~2% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (22.8W) for 5 seconds, for 5 continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the L-507-Z was warm but not hot to the touch.
Our primary measurements revealed the following using the phono-level input, MM configuration (unless specified, assume a 1kHz 5mVrms sinewave input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -63.3dB | -60.0dB |
DC offset | <-2mV | <-2mV |
Gain (default phono preamplifier) | 35.7dB | 35.6dB |
IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-88dB | <-81dB |
IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-92dB | <-87dB |
Input impedance | 50.3k ohms | 52.7k ohms |
Input sensitivity (to rated power with max volume) | 3.15mVrms | 3.19mVrms |
Noise level (with signal, A-weighted) | <290uVrms | <300uVrms |
Noise level (with signal, 20Hz-20kHz) | <700uVrms | <1500uVrms |
Overload margin (relative 5mVrms input, 1kHz) | 30.2dB | 30.4dB |
Signal-to-noise ratio (full rated power, A-weighted) | 90.4db | 89.5dB |
Signal-to-noise ratio (full rated power, 20Hz-20kHz) | 83.1dB | 74.9dB |
THD (unweighted) | <0.003% | <0.005% |
THD+N (A-weighted) | <0.005% | <0.0065% |
THD+N (unweighted) | <0.009% | <0.018% |
Our primary measurements revealed the following using the phono-level input, MC configuration (unless specified, assume a 1kHz 0.5mVrms sinewave input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -58.6dB | -44.1dB |
DC offset | <-2mV | <-2mV |
Gain (default phono preamplifier) | 53.3dB | 53.2dB |
IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-83dB | <-83dB |
IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-79dB | <-79dB |
Input impedance | 140 ohms | 140 ohms |
Input sensitivity (to rated power with max volume) | 417uVrms | 421uVrms |
Noise level (with signal, A-weighted) | <2.2mVrms | <2.5mVrms |
Noise level (with signal, 20Hz-20kHz) | <7mVrms | <14mVrms |
Overload margin (relative 0.5mVrms input, 1kHz) | 32.7dB | 32.7dB |
Signal-to-noise ratio (full rated power, A-weighted) | 72.6dB | 71.5dB |
Signal-to-noise ratio (full rated power, 20Hz-20kHz) | 63.6dB | 56.2dB |
THD (unweighted) | <0.006% | <0.007% |
THD+N (A-weighted) | <0.025% | <0.03% |
THD+N (unweighted) | <0.08% | <0.15% |
Our primary measurements revealed the following using the analog input at the unbalanced headphone output (unless specified, assume a 1kHz sinewave, 2Vrms input and output, 300 ohms loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Maximum output power into 600 ohms (1% THD+N, unweighted) | 405mW | 403mW |
Maximum output power into 300 ohms (1% THD+N, unweighted) | 326mW | 324mW |
Maximum output power into 32 ohms (1% THD+N, unweighted) | 58mW | 58mW |
Gain | 43.6dB | 43.6dB |
Output impedance (1/4″ TRS, unbalanced) | 819 ohms | 821 ohms |
Output impedance (4.4mm TRRS, balanced) | 813 ohms | 815 ohms |
Noise level (with signal, A-weighted) | <40uVrms | <41uVrms |
Noise level (with signal, 20Hz to 20kHz) | <60uVrms | <61uVrms |
Noise level (no signal, A-weighted, volume min) | <5.8uVrms | <6.1uVrms |
Noise level (no signal, 20Hz to 20kHz, volume min) | <7.8uVrms | <9.6uVrms |
Signal-to-noise ratio (max output, A-weighted, 2Vrms in) | 106.3dB | 106.1dB |
Signal-to-noise ratio (max output, 20Hz to 20kHz, 2Vrms in) | 104.1dB | 103.9dB |
THD ratio (unweighted) | <0.007% | <0.017% |
THD+N ratio (A-weighted) | <0.008% | <0.019% |
THD+N ratio (unweighted) | <0.008% | <0.018% |
Frequency response (8-ohm loading, line-level input, relative level)
In our measured frequency-response (relative to 1kHz) chart above, the blue and red plots show the speaker-level outputs (relative to 1kHz, at 10W into 8 ohms). The L-507Z’s speaker outputs are near flat within the audioband (less than -0.1dB at 20Hz and about -0.2dB at 20kHz), and exhibit an average extended bandwidth (-4dB at 100kHz). The L-507Z appears to be AC coupled, due the attenuation in response below 20Hz. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.
Frequency response (8-ohm loading, line-level input, bass and treble controls)
Above is a frequency response (relative to 1kHz) chart with the L-507Z’s bass and treble controls set to maximum and minimum, measured at the speaker-level outputs at 10W into 8 ohms. The L-507Z offers about +/-7dB of bass and treble boost/cut at 20Hz and 20kHz when both controls are engaged fully. When the tone controls are used in isolation, +/-8dB of boost/cut was observed, as advertised by Luxman. Below is . . .
. . . a frequency-response chart (relative to 10kHz) with the bass control set at maximum and minimum while maintaining the treble control at zero. We see a maximum boost/cut of nearly 9dB at 20Hz. Below is . . .
. . . a frequency response chart (relative to 100 Hz) with the treble control set at maximum and minimum while maintaining the bass control at zero. We see a maximum boost/cut of nearly 9dB at 20kHz.
Frequency response (8-ohm loading, line-level input, Loudness control)
Above is a frequency response (relative to 1kHz) chart with the L-507Z’s Loudness control engaged, measured at the speaker-level outputs at 10W into 8 ohms. The L-507Z Loudness control provide a bass boost of 5dB centered at around 80Hz, and a treble boost of just under 4dB, centered at around 15kHz.
Phase response (line-level input)
Above is the phase response plot from 20Hz to 20kHz for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The L-507Z does not invert polarity. Here we find +10 degrees at 20Hz, and -20 degrees at 20kHz.
Frequency response (8-ohm loading, MM phono input)
The chart above shows the frequency response (relative to 1kHz) for the MM phono configuration. What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (i.e., zero deviation would yield a flat line at 0dB). The blue and red traces (left/right) are without the subsonic filter engaged, and the purple and green (left/right) are with the subsonic filter engaged. We see maximum deviations within about ±0.25dB from 20Hz to 20kHz. With the subsonic filter engaged, we find the -3dB point at 30Hz, and at 20Hz, we are at -5dB.
Phase response (MM input)
Above is the phase response plot from 20Hz to 20kHz for the MM phono input, measured across the speaker outputs at 10W into 8 ohms. The blue and red traces (left/right) are without the subsonic filter engaged, and the purple and green (left/right) are with the subsonic filter engaged. The L-507Z does not invert polarity. For the phono input, since the RIAA equalization curve must be implemented, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case of about +60 degrees at 20Hz without the subsonic filter and +120 degrees with the subsonic filter.
Frequency response (8-ohm loading, MM phono input)
The chart above shows the frequency response (relative to 1kHz) for the MC phono configuration. The blue and red traces (left/right) are without the subsonic filter engaged, and the purple and green (left/right) are with the subsonic filter engaged. The responses are essentially identical to the MM configuration above.
Phase response (MC input)
Above is the phase response plot from 20Hz to 20kHz for the MC phono input, measured across the speaker outputs at 10W into 8 ohms. The blue and red traces (left/right) are without the subsonic filter engaged, and the purple and green (left/right) are with the subsonic filter engaged. Here we find a worst case of about +80 degrees at 20Hz without the subsonic filter, and +130 degrees with the subsonic filter.
RMS level vs. frequency vs. load impedance (1W, left channel only)
The chart above shows RMS level (relative to 0dBrA, which is 1W into 8ohms or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .
. . . is the same but zoomed in to highlight differences. Here we can see only minor deviations of about 0.06dB from 4 ohms to no load throughout the audioband. This is an indication of a high damping factor, or low output impedance. The variation in RMS level when a real speaker was used is slightly lower at 0.05dB through most of the audioband.
THD ratio (unweighted) vs. frequency vs. output power
The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sinewave stimulus at the balanced analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at just over 100W. The power was varied using the volume control. At 1W, THD ratios were at their highest and ranged from 0.01% from 20Hz to 100Hz, then up to 0.5% at 20kHz. The left channel outperformed the right (at 10W as well) by a little over 5dB from 300Hz to 20kHz. The 10W THD data ranged from as low as 0.0015% at 30-50Hz, then up to 0.15% at 20kHz. The 100W THD data ranged from 0.007% from 20Hz to 1kHz, then up to 0.04% at 20kHz.
THD ratio (unweighted) vs. frequency at 10W (MM and MC inputs)
The chart above shows THD ratios as a function of frequency plots for the MM (blue/red) and MC (purple/green) phono input configurations measured across an 8-ohm load at 10W. The input sweep is EQ’d with an inverted RIAA curve. The MM THD values varied from as low as 0.003% from 40Hz to 1kHz (left channel), then up to 0.02% at 20kHz. Once again, the right channel yielded higher THD results than the left, at 20-30Hz, and from 500Hz to 20kHz. The MC THD results ranged from 0.05% at 20Hz (left), down to 0.005% at 400-500Hz, then up to 0.01% at 20kHz, with the right channel yielding THD ratios 5-10dB higher at low and high frequencies.
THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD ratios measured at the output of the L-507Z as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). The 8-ohm data outperformed the 4-ohm data by only 2-3dB, smaller than the difference in performance between the left and right channels (5-10dB). The 8-ohm data (left) ranged from 0.02% at 50mW, down to 0.003% at 3-20W, then up to 0.005% at the “knee” at roughly 110W. The “knee” for the 4-ohm data can be seen at roughly 190W. The 1% THD marks are at 135W into 8 ohms, and 222W into 4 ohms.
THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD+N ratios measured at the output of the L-507Z as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Overall, THD+N values for both loads were similar with the 8-ohm data outperforming the 4-ohm data by only 2-3dB. They ranged (left channel) from about 0.05% at 50mW, down to 0.005%.
THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)
The chart above shows THD ratios measured at the output of the L-507Z as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yielded 40W at the output into 8 ohms (and roughly 80W into 4 ohms, and 160W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find a 2-3dB increase in THD from 8 to 4 ohms, then a roughly 5dB increase from 4 to 2 ohms. Nonetheless, even into 2 ohms, these data show that the L-507Z is not only stable into 2-ohm loads, but will yield acceptably low THD values, ranging from 0.005 to 0.06%.
THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows THD ratios measured at the output of the L507-Z as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). At lower frequencies, the two-way speaker yielded the highest THD ratios, as high as 0.04% at 20Hz. From 40Hz to 20kHz however, all THD values were essentially identical, ranging from around 0.01% up to 0.4%. This shows that the L-507Z will yield consistent and stable THD results into different loads at low power levels.
IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows intermodulation distortion (IMD) ratios measured at the output of the L-507Z as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method was used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a two-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are similar enough to be judged identical, hovering at a relatively high 0.02%.
IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows IMD ratios measured at the output of the L-507Z as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method was used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a two-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are similar enough to be judged identical, hovering at a relatively high 0.08%.
FFT spectrum – 1kHz (line-level input, balanced)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the balanced analog line-level input. In general, the even ordered signal harmonics (2/4/6kHz, etc) dominate over the odd (3/5/7kHz, etc.). We see that the signal’s second and fourth harmonics (2/4kHz) dominate at around -90/-80dBrA (left/right), or 0.003/0.01%. The other signal harmonics are below -100dBrA, or 0.001%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 60Hz (right) and 180Hz (left) peaks dominating at and just below -100dBrA, or 0.001%.
FFT spectrum – 1kHz (line-level input, unbalanced)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the unbalanced analog line-level input. The FFT is virtually identical to the FFT shown above using the balanced input.
FFT spectrum – 1kHz (MM phono input)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the MM phono input configuration. Signal harmonics can be seen up to 20kHz, with the 2kHz peak dominating at -90dBRa, or 0.003%. The worst-case power-supply-related peak can be seen at 60Hz, at -90/-70dBrA (left/right), or 0.003/0.03%.
FFT spectrum – 1kHz (MM phono input)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the MC phono input configuration. Signal harmonics can be seen up to 20kHz, with the 2kHz peak dominating at -85dBRa, or 0.006%. The worst-case power-supply-related peak can be seen at 60Hz, at -65/-55dBrA (left/right), or 0.06/0.2%.
FFT spectrum – 50Hz (line-level input)
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s third and fourth harmonics (150/200Hz) dominate at around -100dBrA, or 0.001%. The subsequent signal harmonic peaks are below -110dBrA, or 0.0003%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 60Hz (right) and 180Hz (left) peaks dominating at and just below -100dBrA, or 0.001%.
FFT spectrum – 50Hz (MM phono input)
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the MM phono input configuration. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s second harmonic (100Hz) dominates at around -90dBrA, or 0.003%. The subsequent signal harmonic peaks are below -110dBrA, or 0.0003%. There are clearly visible power-supply related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 60Hz (right) and 180Hz (left) peaks dominating, as high as -70dBrA (right), or 0.03%.
FFT spectrum – 50Hz (MC phono input)
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the MC phono input configuration. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The signal harmonics are barely noticeable above the -100 to -120dBrA noise floor. The second signal harmonic (left) is at -90dBrA, or 0.003%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 60Hz (right) and 180Hz (left) peaks dominating, as high as -55dBrA (right), or 0.2%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -90dBrA, or 0.003%. The third-order modulation products, at 17kHz and 20kHz, are lower at -100dBrA, or 0.001%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MM phono input)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the MM phono input configuration. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -110/100dBrA (left/right), or 0.0003/0.001%. The third-order modulation products, at 17kHz and 20kHz, are around -100dBrA, or 0.001%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MC phono input)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the MC phono input configuration. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is only barely noticeable above the noise floor for the right channel at just below -100dBrA, or 0.001%. The third-order modulation products, at 17kHz and 20kHz, are at an below -100dBrA, or 0.001%.
Intermodulation distortion FFT (line-level input, APx 32 tone)
Shown above is the FFT of the speaker-level outputs of the L-507Z with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the "grass" between the test tones—are distortion products from the amplifier and below the -100dBrA, or 0.001%, level, with the right channel peaks dominating over the left. The peaks at lower frequencies that reach the -100dBrA level are not IMD products but power-supply-related noise peaks.
Square-wave response (10kHz)
Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the L-507Z’s slew-rate performance. Rather, it should be seen as a qualitative representation of the L-507Z’s above average bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (e.g., 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. Here we can see a relatively clean squarewave reproduction, with some mild softening of the corners, and no overshoot.
Damping factor vs. frequency (20Hz to 20kHz)
The final graph above is the damping factor as a function of frequency. Both channels track closely, with a higher damping factor (around 315 to 400) between 20Hz and 2kHz. Above 2kHz, we see a slight decline in the damping factor, as low as 184 at 20kHz.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Todd Whitesel on SoundStage! Simplifi on July 1, 2023
General Information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The Bluesound Powernode Edge was conditioned for 1 hour at 1/8th full rated power (~5W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.
The Edge offers one combination analog/optical input (1/8″ TRS/mini-TosLink), an ethernet connection for streaming, a subwoofer output (RCA), and a pair of speaker-level outputs. For the purposes of these measurements, the following inputs were evaluated: optical (mini-TosLink) S/PDIF and analog line-level unbalanced (1/8″ TRS).
Based on the accuracy and repeatability at various volume levels of the left/right channel matching (see table below), the Edge volume control is likely operating in the digital domain. Consequently, all analog signals are digitized at the Edge’s analog input so the unit may apply volume, bass management, and tone controls. The volume control offers a total range from -51dB to +26dB. Below about 20%, volume increments range from 2.5 to 3.5dB, above 20%, mostly 1dB increments.
Most measurements were made with a 1.7Vrms line-level analog input, or a 0dBFS digital input. We avoided our typical 2Vrms analog input level, because this caused some sporadic noise issues with the Edge’s analog-to-digital converter (ADC). The signal-to-noise ratio (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 40W (8 ohms). For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum, but with a lower input voltage to achieve the same 40W output.
Because the Edge is a digital amplifier technology that exhibits considerable noise above 20kHz (see FFTs below), our typical input bandwidth filter setting of 10Hz–90kHz for frequency sweeps was necessarily changed to 10Hz–22.4kHz for all measurements, except for frequency response and for FFTs. In addition, THD versus frequency sweeps were limited to 6kHz to adequately capture the second and third signal harmonics with the restricted bandwidth setting.
Volume-control accuracy (measured at speaker outputs): left-right channel tracking
Volume position | Channel deviation |
min | 0.3dB |
25% | 0.065dB |
50% | 0.065dB |
75% | 0.065dB |
100% | 0.068dB |
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Bluesound for the Powernode Edge compared directly against our own. The published specifications are sourced from Bluesound’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth is set at its maximum (DC to 1MHz), assume, unless otherwise stated, a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.
Parameter | Manufacturer | SoundStage! Lab |
Rated output power into 8 ohms | 40W | 48W |
IHF Dynamic Power (8 ohms) | 50W | 48W |
IHF Dynamic Power (4 ohms) | 80W | 80W |
THD+N (1kHz, 1W, 8ohm, A-Weighted) | 0.008% | 0.0045% |
Signal-to-noise ratio (A-weighted, 40W, 8-ohm) | 91dB | 97.1dB |
Our primary measurements revealed the following using the analog/optical input (unless specified, assume a 1kHz sinewave at 1.7Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Maximum output power into 8 ohms (1% THD+N, unweighted) | 48W | 48W |
Maximum output power into 4 ohms (1% THD+N, unweighted) | 80W | 80W |
Maximum burst output power (IHF, 8 ohms) | 48W | 48W |
Maximum burst output power (IHF, 4 ohms) | 80W | 80W |
Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |
Crosstalk, one channel driven (10kHz) | -92.4dB | -92.4dB |
Damping factor | 4834 | 2860 |
Clipping no-load output voltage | 21Vrms | 21Vrms |
DC offset | -32mV | -147mV |
Gain (sub-out) | 8.3dB | |
Gain (maximum volume) | 25.8dB | 25.9dB |
IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-72dB | <-72dB |
IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-73dB | <-74dB |
Input impedance (line input, RCA) | 7.7k ohms | 7.7k ohms |
Input sensitivity (for rated power, maximum volume) | 0.915Vrms | 0.910Vrms |
Noise level (with signal, A-weighted) | <148uVrms | <151uVrms |
Noise level (with signal, 20Hz to 20kHz) | <204uVrms | <210uVrms |
Noise level (no signal, volume min, A-weighted) | <79uVrms | <79uVrms |
Noise level (no signal, volume min, 20Hz to 20kHz) | <95uVrms | <99uVrms |
Output Impedance (sub-out) | 220 ohms | |
Signal-to-noise ratio (40W, A-weighted, 1.7Vrms in) | 97.1dB | 97.2dB |
Signal-to-noise ratio (40W, 20Hz to 20kHz, 1.7Vrms in) | 92.3dB | 92.7dB |
Signal-to-noise ratio (40W, A-weighted, max volume) | 94.0dB | 94.1dB |
Dynamic range (40W, A-weighted, digital 24/96) | 102.1dB | 101.9dB |
Dynamic range (40W A-weighted, digital 16/44.1) | 95.4dB | 95.6dB |
THD ratio (unweighted) | <0.0065% | <0.0054% |
THD ratio (unweighted, digital 24/96) | <0.0039% | <0.0031% |
THD ratio (unweighted, digital 16/44.1) | <0.0037% | <0.0029% |
THD+N ratio (A-weighted) | <0.0075% | <0.0063% |
THD+N ratio (A-weighted, digital 24/96) | <0.0045% | <0.0035% |
THD+N ratio (A-weighted, digital 16/44.1) | <0.0047% | <0.0038% |
THD+N ratio (unweighted) | <0.0068% | <0.0058% |
Minimum observed line AC voltage | 122VAC | 122VAC |
For the continuous dynamic power test, the Powernode Edge was able to sustain about 53W into 4 ohms using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (5.3W) for 5 seconds, for 5 continuous minutes. While the Edge can output more than 53W into 4 ohms for short bursts, there is an aggressive thermal and current protection circuit that clamps the output, even if the user keeps increasing the volume. This protection circuit was active during our test.
Frequency response (8-ohm loading, line-level input)
In our measured frequency response (relative to 1kHz) chart above, the Edge is nearly flat within the audioband (20Hz to 20kHz). At the extremes, the Edge is 0.7dB down at 20Hz and 1.5dB down at 20kHz. The Edge cannot be considered a high-bandwidth audio device as the -3dB point is just past 20kHz. In fact, the Edge exhibits brickwall-type filtering just past 20kHz and appears to sample analog signals at 44.1kHz. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.
Frequency response vs. input type (8-ohm loading, left channel only)
The chart above shows the Edge’s frequency response (left channel only) as a function of input type. The green trace is the same analog input data from the previous graph. The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz, the purple trace is for a 24/96 dithered digital input signal from 5Hz to 48kHz, and, finally, pink is 24/192 from 5Hz to 96kHz. The behavior at low frequencies is the same across digital input types: flat down to 5Hz, compared to the -2.5dB at 10Hz for the analog input. The behavior nearing 20kHz is identical for the analog input and the 16/44.1 digital input—about -1.5dB at 20kHz. The behavior for the 24/96 and 24/192 input data was identical, with a -3dB point just past 30kHz, indicating that 24/192 data is likely resampled at 96kHz.
Frequency response (8-ohm loading, line-level input, bass and treble controls)
Above are two frequency-response (relative to 1kHz) plots for the analog input, measured at 10W (8 ohms) at the speaker outputs, with the treble and balance controls set at both minimum and maximum. They show that the Edge will provide a maximum gain/cut of approximately 6dB at 20Hz, and a maximum gain/cut of approximately 6dB at 10kHz.
Frequency response with subwoofer-crossover engaged (120Hz, 8-ohm loading)
Above are two frequency response plots for the analog input, measured at 10W (8 ohms) at the speaker outputs, and at the line-level subwoofer output, with the crossover set at 120Hz. The Edge DSP crossover uses a slope of 18dB/octave, and the subwoofer output is only 0.5dB down at 20Hz.
Phase response (line-level input)
Above is the phase response plot from 20Hz to 20kHz for the analog input from 20Hz to 20kHz. The Edge does not invert polarity and exhibits a little over +40 degrees of phase shift at 20Hz, and almost +80 degrees around 20kHz.
Digital linearity (16/44.1 and 24/96 data)
The chart above shows the results of a linearity test for the optical digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the speaker outputs of the Edge. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response would be a straight flat line at 0dB. Both digital input types performed similarly and flat from -90dBFS down to 0dBFS. The 16/44.1 data overshot the ideal output signal amplitude by only 2-3dB at -120dBFS. The 24/96 data overshot by a significant 26dB at -120dBFS. This appears to be some kind of bug, as the 24/96 signal output amplitude remained at just below -90dBFS, despite the input signal decreasing below this value.
Impulse response (16/44.1 and 24/96 data)
The graph above shows the impulse response for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s) for one sample period then back to digital silence, measured at the speaker outputs (10W at 8 ohms) of the Edge. We can see that the Edge utilizes a typical sinc function reconstruction filter.
J-Test (optical input)
The chart above shows the results of the J-Test test for the optical digital input measured at the speaker outputs (10W into 8 ohms) of the Edge. J-Test was developed by Julian Dunn in the 1990s. It is a test signal—specifically, a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24bit). Since even the first odd harmonic (i.e., 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sinewave. In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (e.g., 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBFS and below. The test file can also be used in conjunction with artificially injected sinewave jitter by the Audio Precision, to show how well the DAC rejects jitter.
We see several and clear peaks in the audioband at -95 to 130dBFS. This is a mediocre J-Test result, and an indication that the Edge DAC may have poor jitter immunity. When sinewave jitter was injected at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection, no further peaks, or worsening of existing peaks, were observed up to about 700ns of jitter level, where the Edge lost sync on the signal.
Wideband FFT spectrum of white noise and 19.1kHz sine-wave tone (optical input)
The chart above shows a fast Fourier transform (FFT) of the Edge’s speaker outputs (10W into 8 ohms) with white noise at -4dBFS (blue/red) and a 19.1 kHz sinewave at 0dBFS fed to the optical digital input, sampled at 16/44.1. The sharp roll-off above 20kHz in the white-noise spectrum shows the implementation of a brickwall-type reconstruction filter. There are a few low-level aliased image peaks in the audioband at -125dBrA and below. The main 25kHz alias peak is highly suppressed at -110dBrA.
RMS level vs. frequency vs. load impedance (1W, left channel only)
The chart above shows RMS level (relative to 0dBrA, which is 1W into 8 ohms or 2.83Vrms) as a function of frequency, for the analog input swept from 10Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .
. . . is the same but zoomed in to highlight differences. Zoomed in, we can see a maximum deviation within the audioband of about 0.005dB from 4 ohms to no load, which is an indication of an extremely high damping factor, or vanishingly low output impedance. The maximum variation in RMS level when a real speaker was used is difficult to decipher, because the variations we see (due to the extreme zooming in the graph) are inherent frequency-response variations, not due to the amplifier output impedance interacting with speaker impedance.
THD ratio (unweighted) vs. frequency vs. output power
The chart above shows THD ratios at the output into 8 ohms as a function of frequency (20Hz to 6kHz) for a sinewave stimulus at the analog input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 40W (rated power). The power was varied using the volume control. All three THD plots are relatively flat and similar, hovering around 0.005 to 0.01%.
THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD ratios measured at the output of the Edge as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Although there are fluctuations below 3W, both the 4-ohm and 8-ohm data are essentially the same (0.002 to 0.006%) from 3W to the “knees” at about 43W (8 ohms) and just below 70W (4 ohms). As is typical, THD ratios were highest with the lowest signal amplitude, at just above (4 ohms) and below (8 ohms) 0.2% at 10mW.
THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD+N ratios measured at the output of the Edge as a function of output power for the analog line level-input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). There’s a distinct 5dB jump in THD+N (also visible in the THD plot above) when the output voltage is around 1Vrms (i.e., 0.15W into 8 ohms, 0.3W into 4 ohms). This behavior was repeatable over multiple measurement trials. Overall, THD+N values before the “knee” ranged from around 0.02-0.01% (0.5 to 40W into 8 ohms and 0.5 to 70W into 4 ohms) to up to 1-2% at 10mW.
THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)
The chart above shows THD ratios measured at the output of the Edge as a function of load (8/4/2 ohms) for a constant input voltage that yielded 5W at the output into 8 ohms (and roughly 10W into 4 ohms, and 20W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find identical THD ratios between the 8- and 4-ohm loads, hovering around 0.005%. Since the Edge is not designed to drive 2-ohm loads, predictably, THD ratios were much higher into 2 ohms, at 0.2%, dipping down to 0.03% at 6kHz.
THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows THD ratios measured at the output of the Edge as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are similar enough to be judged identical, yielding THD ratios around 0.005% from 20Hz to 6kHz. This is an extraordinary result and a first since we have been conducting this test. Typically, fluctuations of 20dB or more are oberved between the resistive dummy load and real speakers. This is a testament to the Edge’s extremely high damping factor (see last graph).
IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows intermodulation distortion (IMD) ratios measured at the output of the Powernode Edge as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method is used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are similar enough to be judged identical, yielding IMD ratios from around 0.005% up to 0.02%.
IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows IMD ratios measured at the output of the Powernode Edge as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method is used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are similar enough to be judged identical, yielding IMD ratios just below 0.02% across the frequency sweep.
FFT spectrum – 1kHz (line-level input)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s second (2kHz) and third (3kHz) harmonics dominate at -90dBrA or 0.003%; the remaining signal harmonics are at or below -110dBrA, or 0.0003%. Below 1kHz, we see power-supply noise-related peaks at 60Hz and 180Hz, at -100 dBrA, or 0.001%, and -115dBrA, or 0.0002%, respectively. Other lower-level noise-related peaks can also be seen. There is a significant rise in the noise floor just above 20kHz, typical for many class-D amps.
FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the optical digital input, sampled at 16/44.1. The main difference compared to the analog input FFT above is the lower second (2kHz) harmonic peak at -110dBrA, or 0.0003%. Power-supply noise-related peaks are little worse here, reaching -90dBrA (right channel) at 60Hz, or 0.003%.
FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the optical digital input, sampled at 24/96. We see essentially the same signal harmonic profile as with the 16/44.1 FFT above, but with a slightly lower noise floor due to increased bit-depth.
FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)
Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sinewave stimulus at the optical digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and the second (2kHz) harmonic just barely peaking above the -135dBrA noise floor for the right channel. The 60Hz power-supply-related peak is at -120/110dBrA (left/right), or 0.0001/0.0003%.
FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)
Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sinewave stimulus at the optical digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and the signal’s harmonics (2/3/4/5/6kHz, etc.) at -100dBrA, or 0.001% and below, with the fifth (5kHz) harmonic peak dominating.
FFT spectrum – 50Hz (line-level input)
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the analog input. The X axis is zoomed in from 40 Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most predominant (non-signal) peak is the signal second harmonic (100Hz) at -90dBrA, or 0.003%, with other signal harmonics seen below -100dBrA, or 0.001%. Very small power-supply-related peaks can be seen, for example at 180Hz, at just above -120dBrA, or 0.0001%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the analog input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -100dBRa, or 0.001%, while the third-order modulation products, at 17kHz and 20kHz, are higher, at around -85dBrA, or 0.006%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, optical digital input, 16/44.1)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital optical input at 16/44.1. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -110dBRA, or about 0.0003%, while the third-order modulation products, at 17kHz and 20kHz are at -95dBrA, or 0.002%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, optical digital input, 24/96)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital optical input at 24/96. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -110dBRA, or about 0.0003%, while the third-order modulation products, at 17kHz and 20kHz, are at -95dBrA, or 0.002%.
Intermodulation distortion FFT (analog line-level input, APx 32 tone)
Shown above is the FFT of the speaker-level output of the Edge with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the "grass" between the test tones—are distortion products from the amplifier and are below the -125dBrA, or 0.00006%, level.
Square-wave response (10kHz)
Above is the 10kHz squarewave response using the analog input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the Edge’s slew-rate performance. Rather, it should be seen as a qualitative representation of its very limited bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (e.g., 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. Due to Edge’s very limited bandwidth, only the squarewave’s fundamental (10kHz) sinewave is reproduced here. In addition, we can see the 500kHz switching-oscillator frequency used in the digital-amplifier section clearly visible modulating the waveform.
Square-wave response (1Hz–250kHz bandwidth)
Above is the 1kHz squarewave response using the analog input, at roughly 10W into 8 ohms, with a 250kHz restricted bandwidth to remove the modulation from the 500kHz oscillator. We see more evidence here, in the overshoot and undershoot at the squarewave corners, of the Edge’s limited bandwidth with an analog input.
FFT spectrum of 400kHz switching frequency relative to a 1kHz tone
The Edge’s class-D amplifier relies on a switching oscillator to convert the input signal to a pulse-width modulated (PWM) squarewave (on/off) signal before sending the signal through a low-pass filter to generate an output signal. The Edge oscillator switches at a rate of about 500kHz, and this graph plots a wide bandwidth FFT spectrum of the amplifier’s output at 10W into 8 ohms as it’s fed a 1kHz sinewave. We can see that the 500kHz peak is quite evident, and at -60dBrA. There is also a peak at 1MHz (the second harmonic of the 500kHz peak), at -55dBrA. Those peaks are direct results of the switching oscillators in the Edge amp modules. The noise around those very-high-frequency signals are in the signal, but all that noise is far above the audioband—and therefore inaudible—and so high in frequency that any loudspeaker the amplifier is driving should filter it all out anyway.
Damping factor vs. frequency (20Hz to 20kHz)
The final plot above is the damping factor as a function of frequency. Both channels show deviations across the frequency sweep, but this may be due to a higher uncertainty due to the extremely small differences in voltages that were required to be measured for this test. Damping factors were as high as 8000 (left channel at 3kHz), and as low as 330 at 20kHz. These are the highest damping factors we have ever measured.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Roger Kanno on SoundStage! Hi-Fi on June 15, 2023
General Information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The Yamaha R-N2000A was conditioned for 1 hour at 1/8th full rated power (~11W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.
The R-N2000A offers three unbalanced line-level analog inputs (RCA), one unbalanced phono input (RCA) for a moving-magnet (MM) cartridge, one coaxial (RCA) and two optical (TosLink) S/PDIF digital inputs, a Bluetooth input, one line-level subwoofer output (RCA), two line-level pre-outs (RCA), and two pair of speaker-level outputs (A and B). On the front of the unit is a 1/4″ TRS headphone output, and a Pure Direct button, which, when engaged, disables all DSP and tone controls. For the purposes of these measurements, the following inputs were evaluated: digital coaxial, and the analog line-level and MM unbalanced inputs, with the Pure Direct switch engaged.
Most measurements were made with a 2Vrms line-level analog input, 5mVrms MM input, and 0dBFS digital input. The signal-to-noise ratio (SNR) measurements were made with the same input-signal values but with the volume set to achieve the rated output power of 90W (8 ohms). For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum, but with a lower input voltage to achieve the same 90W output.
Based on the accuracy and non-repeatable results at various volume levels of the left/right channel matching (see table below), the R-N2000A volume control is likely digitally controlled but operating in the analog domain. The volume control offers a total range from -53.6dB to +42.7dB between the line-level analog input and the speaker outputs in 0.5dB steps.
The analyzer’s input bandwidth filter was set to 10Hz –22.4kHz for all measurements, except for frequency response (DC to 1MHz), FFTs (10Hz to 90kHz), and THD vs. frequency (10Hz –90kHz). The latter to capture the second and third harmonic of the 20kHz output signal. Since the R-N2000A is a conventional class-AB amp, there was no issue with excessive noise above 20kHz like there would be with a class-D design.
Volume-control accuracy (measured at speaker outputs): left-right channel tracking
Volume position | Channel deviation |
-96.5dB (min) | 0.004dB |
-80dB | 0.036dB |
-70dB | 0.04dB |
-60dB | 0.045dB |
-50dB | 0.045dB |
-40dB | 0.025dB |
-30dB | 0.022dB |
-20dB | 0.028dB |
-10dB | 0.008dB |
max (0dB) | 0.02dB |
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Yamaha for the R-N2000A compared directly against our own. The published specifications are sourced from Yamaha’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended from DC to 1MHz, assume, unless otherwise stated, 10W into 8ohms and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.
Parameter | Manufacturer | SoundStage! Lab |
Rated output power into 8 ohms (0.07% THD) | 90W | 86W |
Rated output power into 4 ohms (0.07% THD) | 145W | 141W |
Maximum power (8 ohms, 10% THD) | 120W | 108W |
IHF Burst Power (8/4 ohms) | 100/185W | 100.7/181.4W |
Frequency response (5Hz - 100kHz) | 0/-3dB | -0.1/-0.56dB |
SNR (A-weighted, rated output, CD input) | 110dB | 111.6dB |
Our primary measurements revealed the following using the line-level analog input and digital coaxial input (unless specified, assume a 1kHz sinewave at 2Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Maximum output power into 8 ohms (1% THD+N, unweighted) | 90W | 90W |
Maximum output power into 4 ohms (1% THD+N, unweighted) | 149W | 149W |
Maximum burst output power (IHF, 8 ohms) | 100.7W | 100.7W |
Maximum burst output power (IHF, 4 ohms) | 181.4W | 181.4W |
Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |
Crosstalk, one channel driven (10kHz) | -80.1dB | -90.6dB |
Damping factor | 279 | 295 |
Clipping no-load output voltage | 29.7Vrms | 29.7Vrms |
DC offset | <-9.8mV | <-2.7mV |
Gain (pre-out) | 14.3dB | 14.4dB |
Gain (maximum volume) | 42.7dB | 42.7dB |
IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-75dB | <-75dB |
IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-71dB | <-71dB |
Input impedance (line input, RCA) | 54.6k ohms | 55.4k ohms |
Input sensitivity (for rated power, maximum volume) | 200mVrms | 200mVrms |
Noise level (with signal, A-weighted) | <69uVrms | <72uVrms |
Noise level (with signal, 20Hz to 20kHz) | <97uVrms | <208uVrms |
Noise level (no signal, A-weighted, volume min) | <49uVrms | <49uVrms |
Noise level (no signal, 20Hz to 20kHz, volume min) | <63uVrms | <72uVrms |
Output Impedance (pre-out) | 1325 ohms | 1326 ohms |
Signal-to-noise ratio (90W, A-weighted, 2Vrms in) | 111.6dB | 111.7dB |
Signal-to-noise ratio (90W, 20Hz to 20kHz, 2Vrms in) | 109.5dB | 108.9dB |
Signal-to-noise ratio (90W, A-weighted, max volume) | 100.4dB | 100.4dB |
Dynamic range (90W, A-weighted, digital 24/96) | 111.2dB | 111.4dB |
Dynamic range (90W A-weighted, digital 16/44.1) | 96.0dB | 95.9dB |
THD ratio (unweighted) | <0.0054% | <0.0054% |
THD ratio (unweighted, digital 24/96) | <0.0063% | <0.0058% |
THD ratio (unweighted, digital 16/44.1) | <0.0063% | <0.0058% |
THD+N ratio (A-weighted) | <0.0061% | <0.0061% |
THD+N ratio (A-weighted, digital 24/96) | <0.0062% | <0.0062% |
THD+N ratio (A-weighted, digital 16/44.1) | <0.0069% | <0.0066% |
THD+N ratio (unweighted) | <0.0055% | <0.0058% |
Minimum observed line AC voltage | 123.4VAC | 123.4VAC |
For the continuous dynamic power test, the R-N2000A was able to sustain 170W into 4 ohms (~3% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (17W) for 5 seconds, for 5 continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the R-N2000A was only slightly warm to the touch.
Our primary measurements revealed the following using the phono-level input, MM configuration (unless specified, assume a 1kHz 5mVrms sinewave input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -75.3dB | -71.4dB |
DC offset | <-8mV | <-1mV |
Gain (default phono preamplifier) | 35.3dB | 35.3dB |
IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-69dB | <-69dB |
IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-74dB | <-74dB |
Input impedance | 53.1k ohms | 52.3k ohms |
Input sensitivity (to max power with max volume) | 3.4mVrms | 3.4mVrms |
Noise level (with signal, A-weighted) | <860uVrms | <860uVrms |
Noise level (with signal, 20Hz to 20kHz) | <2.4mVrms | <2.4mVrms |
Noise level (no signal, A-weighted, volume min) | <49uVrms | <49uVrms |
Noise level (no signal, 20Hz to 20kHz, volume min) | <63uVrms | <63uVrms |
Overload margin (relative 5mVrms input, 1kHz) | 23.4dB | 23.3dB |
Signal-to-noise ratio (90W, A-weighted, 5mVrms in) | 79.2dB | 79.3dB |
Signal-to-noise ratio (90W, 20Hz to 20kHz, 5mVrms in) | 71.6dB | 71.8dB |
Signal-to-noise ratio (90W, A-weighted, max volume) | 75.8dB | 75.8dB |
THD (unweighted) | <0.0088% | <0.0088% |
THD+N (A-weighted) | <0.014% | <0.014% |
THD+N (unweighted) | <0.03% | <0.03% |
Our primary measurements revealed the following using the analog input at the headphone output (unless specified, assume a 1kHz sinewave, 2Vrms output, 300 ohms loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Maximum output power into 600 ohms (1% THD+N, unweighted) | 48mW | 48mW |
Maximum output power into 300 ohms (1% THD+N, unweighted) | 60mW | 60mW |
Maximum output power into 32 ohms (1% THD+N, unweighted) | 26mW | 26mW |
Gain | 32.3dB | 32.3dB |
Output impedance | 97.7 ohms | 98.5 ohms |
Noise level (no signal, A-weighted, volume min) | <11uVrms | <11uVrms |
Noise level (no signal, 20Hz to 20kHz, volume min) | <14uVrms | <14uVrms |
Signal-to-noise ratio (Max Output, A-weighted, 2Vrms in) | 107.1dB | 107.1dB |
Signal-to-noise ratio (Max Output, 20Hz to 20kHz, 2Vrms in) | 105.0dB | 105.0dB |
THD ratio (unweighted) | <0.0079% | <0.0071% |
THD+N ratio (A-weighted) | <0.0091% | <0.0081% |
THD+N ratio (unweighted) | <0.0081% | <0.0072% |
Frequency response (8-ohm loading, line-level input, relative level)
In our measured frequency response chart above, the blue and red plots show the speaker-level outputs (relative to 1kHz, at 10W into 8 ohms), while the purple plot (relative to 20Hz) is the line-level subwoofer output. The R-N2000A’s speaker outputs are essentially flat within the audioband (0dB at 20Hz, -0.04dB at 20kHz), and show an extended bandwidth (-0.1dB at 5Hz, -0.44dB at 80kHz). The subwoofer output is low-pass filtered, with a -3dB point at roughly 500Hz and a 12dB/octave slope. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.
Frequency response (8-ohm loading, line-level input, Pure Direct off)
The measured frequency response (relative to 1kHz) chart above shows the R-N2000A speaker-level outputs (10W into 8 ohms) with the Pure Direct switch disengaged. In this mode, the analog signal is digitized at what likely is a 96kHz sample rate (-3dB point just past 40kHz). At the extremes of the audioband, the response is at roughly -0.25dB at both 20Hz and 20kHz.
Frequency response (8-ohm loading, line-level input, bass and treble controls)
Above are frequency response plots (relative to 1kHz) measured at the speaker-level outputs into 8 ohms, with the bass and treble controls set to maximum (blue/red plots) and minimum (purple/green plots). We see that for the bass and treble controls, roughly +/-9dB respectively of gain/cut are available at 20Hz and 20kHz.
Phase response (line-level input)
Above is the phase response plot from 20Hz to 20kHz for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The R-N2000A does not invert polarity. Here we find essentially no phase shift within the audioband, owing to the R-N2000A’s extended bandwidth.
Frequency response vs. input type (8-ohm loading, left channel only)
The chart above shows the R-N2000A’s frequency response (relative to 1kHz) as a function of input type measured across the speaker outputs at 10W into 8 ohms. The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 10Hz to 22kHz using the coaxial digital input, and the purple trace is for a 24/96 dithered digital input signal from 10Hz to 48kHz, while the pink trace is for a 24/192 dithered digital input signal from 10Hz to 96kHz. The green trace is the same analog input frequency response seen above. The 16/44.1 data exhibits not quite brick-wall-type filtering, with a -3dB point at 19.7kHz. The 24/96 and 24/192 kHz data yielded -3dB points at 42.3kHz and 80.8kHz, respectively.
Frequency response (8-ohm loading, MM phono input)
The chart above shows the frequency response (relative to 1kHz) for the MM phono input. What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (i.e., zero deviation would yield a flat line at 0dB). We see maximum deviations within about ±0.1dB from 20Hz to 20kHz.
Phase response (MM input)
Above is the phase response plot from 20Hz to 20kHz for the MM phono input, measured across the speaker outputs at 10W into 8 ohms. The R-N2000A does not invert polarity. For the phono input, since the RIAA equalization curve must be implemented, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case of about -60 degrees at 200Hz and 5kHz.
Digital linearity (16/44.1 and 24/96 data)
The chart above shows the results of a linearity test for the coaxial digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the line-level pre-outs of the R-N2000A for a 1.93Vrms (at 0dBFS) output signal. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response would be a straight flat line at 0dB. Both data were essentially perfect as of -100dBFS down to 0dBFS. At -120dBFS, the 16/44.1 data were about +2dB (left/right) above reference, while the 24/96 data were still at the reference 0dB level. To verify the performance of the 24/96 data, we extended the sweep down to . . .
. . . -140dB. The chart above shows that the 24/96 data yielded worst-case deviations of +2dB above reference, even at -140dB. This is an exceptional result. The 16/44.1 data deviates substantially, which is expected.
Impulse response (24/44.1 data)
The graph above shows the impulse response for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s) for one sample period then back to digital silence, measured at the fixed line-level pre-outs of R-N2000A. We can see that the R-N2000A utilizes a typical symmetrical sinc function reconstruction filter.
J-Test (coaxial)
The chart above shows the results of the J-Test test for the coaxial digital input measured at the line-level pre-outs of the R-N2000A. J-Test was developed by Julian Dunn in the 1990s. It is a test signal—specifically, a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (i.e., 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sinewave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (e.g., 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA and below. The test file can also be used in conjunction with artificially injected sinewave jitter by the Audio Precision, to show how well the DAC rejects jitter.
The coaxial input exhibits a few low-level peaks in the audioband, most of which are under -140dBrA. This is a strong J-test result, indicating that the R-N2000A DAC should be adequate at rejecting jitter.
J-Test (optical)
The chart above shows the results of the J-Test test for the optical digital input measured at the fixed line-level pre-outs of the R-N2000A. Essentially the same result as with the coax input can be seen.
J-Test with 100ns of injected jitter (coaxial)
Both the coaxial and optical inputs were also tested for jitter immunity by injecting artificial sinewave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. The optical input jitter result was very similar to the coaxial input result shown above. Jitter immunity proved strong. Although sidebands were visible at the 100ns jitter level, they did not exceed -145dBrA in amplitude.
J-Test with 500ns of injected jitter (coaxial)
Both the coaxial and optical inputs were also tested for jitter immunity by injecting artificial sinewave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. The optical input jitter result was very similar to the coaxial input result shown above. Jitter immunity again proved to be solid but not perfect, with visible sidebands at a very low -135dBrA at the 300ns jitter level. The R-N2000A DAC did lose sync with the signal when jitter was increased beyond approximately 400ns.
Wideband FFT spectrum of white noise and 19.1kHz sinewave tone (coaxial input)
The plot above shows a fast Fourier transform (FFT) of the R-N2000A’s line-level pre-outs with white noise at -4 dBFS (blue/red), and a 19.1 kHz sinewave at 0dBFS fed to the coaxial digital input, sampled at 16/44.1. The medium roll-off above 20kHz in the white-noise spectrum shows the implementation of a reconstruction filter that isn’t quite as steep as a typical brickwall type. There are two clear aliased image peaks in the audio band above the -135dBrA noise floor at 13kHz (-95dBrA) and 6kHz (-115dBrA). The main 25kHz alias peak is only mildly suppressed at -30dBrA. The second, third, and fourth distortion harmonics (38.2, 57.3, 76.4kHz) of the 19.1kHz tone are between -65dBrA and -90dBrA.
RMS level vs. frequency vs. load impedance (1W, left channel only)
The chart above shows RMS level (relative to 0dBrA, which is 1W into 8ohms or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .
. . . is the same but zoomed in to highlight differences. Here we can see only minor deviations of about 0.06dB from 4 ohms to no load through most of the audioband, reaching as high as 0.17dB at 20kHz. This is an indication of a relatively high damping factor, or low output impedance. The variations in RMS level when a real speaker was used are smaller, deviating by at worst 0.04dB through most of the audioband.
THD ratio (unweighted) vs. frequency vs. output power
The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sinewave stimulus at the analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 80W. The power was varied using the volume control. At 1W, THD ratios ranged from 0.007% at 20Hz, down to 0.002% at 6kHz. At 1 and 10W, THD ratios were similar, and the right channel outperformed the left by 3–5dB. Right channel THD ratios ranged from about 0.006% at 20Hz, down to 0.004–0.005% from 50Hz to 3kHz, then up to just above 0.01% at 20kHz. The 80W THD values were slightly higher and ranged from 0.008% at 20Hz through to about 3kHz, then up to 0.03% at 20kHz.
THD ratio (unweighted) vs. frequency at 10W (MM input)
The chart above shows THD ratios as a function of frequency plots for the MM phono input measured across an 8-ohm load at 10W. The input sweep is EQ’d with an inverted RIAA curve. The THD values vary from around 0.02% (20Hz) down to 0.005% at 300–2kHz, then up to 0.03% at 20kHz.
THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD ratios measured at the output of the R-N2000A as a function of output power for the analog line level-input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). The 8-ohm and right channel 4-ohm data track perfectly from 50mW to 3W, ranging from 0.002% to 0.005%. The left channel 4-ohm data were 5-10dB higher in this range. From 3W to 30W, there is jump in THD from the right channel 4-ohm data, by about 10dB. This phenomenon was repeatable. At 50W to about 80W, all THD data were nearly identical at about 0.07%. The “knee” for the 8-ohm data is around 70W, then up to the 1% THD mark at the rated 90W. With a 4-ohm load, the “knee” occurs at about 130W, and the 1% THD value was reached at 149W.
THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD+N ratios measured at the output of the R-N2000A as a function of output power for the analog line level-input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Overall, THD+N values for both loads were similar (with the exception of the 10dB jump in THD from the right channel into 4 ohms from 3W to 30W), ranging from about 0.02%, down to just above 0.005% (8-ohm). The 4-ohm left channel THD+N ratios were a few dB worse than the 8-ohm ratios through most of the sweep.
THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)
The chart above shows THD ratios measured at the output of the R-N2000A as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yielded 10W at the output into 8 ohms (and roughly 20W into 4 ohms, and 40W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find all three traces yielding similar results, remarkably, with the 2-ohm THD data out-performing the 4-ohm data by 2–3dB, and nearly matching the 8-ohm data. The exception is at 20Hz and 20kHz, where the 2-ohm data were about 5dB worse than the 8-ohm. We find the 8-ohm trace ranging from 0.005% from 20Hz up to 3kHz, then up to 0.02% at 20kHz. These data show that the R-N2000A is not only stable into 2-ohm loads, but will perform nearly identically, in terms of THD, to an 8-ohm load.
THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows THD ratios measured at the output of the R-N2000A as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). At lower frequencies, the two-way speaker yielded the highest THD ratios, as high as 0.05% at 20Hz, but as low as 0.0015% at 2-3kHz. Overall, however, THD ratios were mostly within 5dB of the 8-ohm THD data, sometimes above, sometimes below. This shows once again, that the R-N2000A will yield consistent and stable THD results into different loads.
IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows intermodulation distortion (IMD) ratios measured at the output of the R-N2000A as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method is used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second- (F1-F2 or 1kHz) and third-modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). The results for the dummy load were fairly consistent, hovering around 0.01% throughout the sweep. We find that the two-way speaker yielded IMD ratios 5-15dB lower than the dummy load, ranging from 0.002% at 2.5kHz and 0.005% at 20kHz. The 3-way speaker yielded IMD ratios roughly 10dB lower than the dummy load at lower frequences, and 5dB higher at higher frequencies.
IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows IMD ratios measured at the output of the R-N2000A as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method is used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are similar, at or below the 0.02% level. The two-way speaker IMD result dipped as low as 0.006% at 80Hz, while the three-way speaker IMD result dipped as low as 0.008% just below 60Hz.
FFT spectrum – 1kHz (line-level input)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s third harmonic (3kHz) dominates at around -85dBrA, or 0.006%. The other signal harmonics are around or below -100dBrA, or 0.001%. There are clearly visible power-supply related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 120Hz peak dominating at -110/-95dBrA (left/right), or 0.0003/0.002%.
FFT spectrum – 1kHz (line-level input, Pure Direct off)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input, with the Pure Direct switch disengaged (incoming analog signal digitized). Compared to the FFT above, with Pure Direct engaged, signal distortion peaks are higher here, with the third harmonic (3kHz) reaching almost -75dBrA, or 0.02%, compared to the -85dBrA seen in the FFT above. Power-supply-related noise peaks are similar here compared to the FFT above; however, the 60Hz peak is slightly more predominant here at -110dBrA, or 0.0003%, versus the -115dBrA seen above with Pure Direct engaged. We can also see here, the peaks at 96kHz from the sample rate used to digitize the incoming analog signal.
FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 16/44.1. The signal and noise-related harmonics are very similar to the FFT above for the analog input, with the exception of the levels for the second (2kHz) and third (3kHz) signal harmonics. Here we find them both at about -90dBrA, or 0.003%, versus the -100dBrA (2kHz) and -85dBrA (3kHz) levels seen in the analog input FFT.
FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 24/96. The signal and noise-related harmonics are very similar to the 16/44.1 FFT above, but for a slightly lower noise here due to the 24-bit depth.
FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)
Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and non-existent signal harmonics. Power-supply related noise peaks can be seen at the fundamental (60Hz) and higher harmonics, at -105dBrA, or 0.0006%, and below.
FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)
Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and virtually non-existent signal harmonics. Power-supply-related noise peaks can be seen at the fundamental (60Hz) and higher harmonics, at -105dBrA, or 0.0006%, and below.
FFT spectrum – 1kHz (MM phono input)
Shown above is the FFT for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the MM phono input. We see that the signal’s third harmonic (3kHz) dominates at around -85dBrA, or 0.006%. The 2kHz peak is very low at -110dBrA, or 0.0003%, and subsequent signal harmonics are at -95dBrA, or 0.002%, and below. There are clearly visible power-supply-related noise peaks on the left side of the main 1kHz peak, with the 60Hz fundamental dominating at -90/-80dBrA (left/right channels), or 0.003/0.01%.
FFT spectrum – 50Hz (line-level input)
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s third harmonic (150Hz) dominates at around -90dBrA, or 0.003%. The second signal harmonic (100Hz), and subsequent signal harmonic peaks, are at or below -100dBrA, or 0.001%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 120Hz peak dominating at -110/-95dBrA (left/right channels), or 0.0003/0.002%.
FFT spectrum – 50Hz (MM phono input)
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the MM phono input. The X axis is zoomed in from 40 Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s third harmonic (150Hz) dominates at around -85dBrA, or 0.006%. The even-order signal harmonic (100, 200Hz, etc.) are barely perceptible above the -110 to -120dBrA noise floor, and subsequent odd-order signal harmonic peaks (250Hz, 350Hz, etc.) are at or below -100dBrA, or 0.001%. The most dominant power-supply-related noise peak is at the fundamental (60Hz) at -80dBrA (right channel), or 0.01%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -105/110dBrA (left/right channels), or 0.0006/0.0003%. The third-order modulation products, at 17kHz and 20kHz, are higher at -85dBrA, or 0.006%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 16/44.1)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 16/44.1. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is just above -100dBrA, or 0.001%. The third-order modulation products, at 17kHz and 20kHz, are at higher at -85dBrA, or 0.006%. Also visible are the IMD peaks from the 44.1kHz sample rate and the primary peaks at 25.1 and 26.1kHz.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 24/96)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 24/96. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -95dBrA, or 0.002%. The third-order modulation products, at 17kHz and 20kHz, are at higher at -85dBrA, or 0.006%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MM phono input)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the MM phono input. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is just above -80dBrA, or 0.01%. The third-order modulation products, at 17kHz and 20kHz, are at around -90dBrA, or 0.003%.
Square-wave response (10kHz)
Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the R-N2000A’s slew-rate performance. Rather, it should be seen as a qualitative representation of the R-N2000A’s extended bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (e.g., 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. Here we can see a clean squarewave reproduction, with only very mild softening of the corners, and no overshoot.
Damping factor vs. frequency (20Hz to 20kHz)
The final graph above is the damping factor as a function of frequency. Both channels track closely, with a higher damping factor (around 280 to 300) between 20Hz and 2kHz. Above 2kHz, we see a decline in the damping factor, as low as 150 at 20kHz.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Dennis Burger on SoundStage! Access on May 1, 2023
General Information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The Pro-Ject Audio Systems MaiA DS3 was conditioned for 1 hour at 1/8th full rated power (~10W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.
The MaiA DS3 offers three unbalanced line-level analog inputs (RCA); one unbalanced phono input (RCA) for moving-magnet (MM) or moving-coil (MC) cartridges (selectable with a switch on the rear panel); one coaxial S/PDIF (RCA), two optical S/PDIF (TosLink), and one USB digital input; a Bluetooth input; one line-level subwoofer output (RCA); two line-level pre-outs (RCA, fixed and variable); and a pair of speaker-level outputs. On the front of the unit are a 1/4″ TRS headphone output and a +6dB gain switch for the preamp section. For the purposes of these measurements, the following inputs were evaluated: digital coaxial and the analog line-level and MM/MC unbalanced inputs, with the +6dB gain switch engaged.
Most measurements were made with a 2Vrms line-level analog input, 5mVrms MM input, 0.5mVrms MC input, and 0dBFS digital input. The signal-to-noise ratio (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 80W (8 ohms). For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum, but with a lower input voltage to achieve the same 80W output.
Based on the inaccuracy and non-repeatable results at various volume levels of the left/right channel matching (see table below), the MaiA DS3 volume control is likely a potentiometer operating in the analog domain. The volume control offers a total range from -66dB to +35.2dB between the line-level analog input and the speaker outputs, with the +6dB switch engaged.
The analyzer’s input bandwidth filter was set to 10Hz–22.4kHz for all measurements, except for frequency-response and FFT charts. Because the MaiA DS3 is a digital amplifier technology that exhibits considerable noise above 20kHz (see FFTs below), the 22.4kHz bandwidth setting was maintained for THD versus frequency sweeps as well. For these sweeps, the highest frequency was 6kHz, to adequately capture the second and third signal harmonics with the restricted-bandwidth setting.
Volume-control accuracy (measured at speaker outputs): left-right channel tracking
Volume position | Channel deviation |
min | 0.8dB |
7 o'clock | 0.045dB |
9 o'clock | 0.773dB |
10 o'clock | 0.578dB |
12 o'clock | 0.756dB |
1 o'clock | 0.779dB |
3 o'clock | 0.678dB |
4 o'clock | 0.334dB |
max | 0.039dB |
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Pro-Ject for the MaiA DS3 compared directly against our own. The published specifications are sourced from Pro-Ject’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended from DC to 250kHz, assume, unless otherwise stated, 10W into 8ohms and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.
Parameter | Manufacturer | SoundStage! Lab |
Rated output power into 8 ohms (1% THD) | 80W | 80W |
Rated output power into 4 ohms (1% THD) | 140W | 143W |
Frequency response (20Hz - 20kHz, 4 ohms) | <±0.3dB at 20kHz | -1dB at 20kHz |
THD (1kHz, 10W, 8 ohms) | <0.01% | <0.0072% |
SNR (A-weighted, rated output) | 105dB | 107dB |
Input sensitivity (line level, max volume for rated output) | 860mVrms | 883mVrms |
Headphone rated output power into 32 ohms (1% THD) | 430mW | 401mW |
Phono input impedance (MM) | 47k ohms | 52.6k ohms |
Phono input impedance (MC) | 100 ohms | 141 ohms |
Phono gain (MM) | 40dB | 45dB |
Phono gain (MC) | 60dB | 63dB |
Our primary measurements revealed the following using the line-level analog input and digital coaxial input (unless specified, assume a 1kHz sinewave at 2Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Maximum output power into 8 ohms (1% THD+N, unweighted) | 80W | 80W |
Maximum output power into 4 ohms (1% THD+N, unweighted) | 144W | 143W |
Maximum burst output power (IHF, 8 ohms) | 80W | 80W |
Maximum burst output power (IHF, 4 ohms) | 144W | 143W |
Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |
Crosstalk, one channel driven (10kHz) | -61.8dB | -60.6dB |
Damping factor | 85 | 80 |
Clipping no-load output voltage | 26.5Vrms | 26.5Vrms |
DC offset | <10mV | <10mV |
Gain (pre-out) | 3.3/9.4dB | 3.3/9.4dB |
Gain (maximum volume) | 29.2/35.2dB | 29.2/35.3dB |
IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-74dB | <-75dB |
IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-76dB | <-76dB |
Input impedance (line input, RCA) | 24k ohms | 25k ohms |
Input sensitivity (for rated power, maximum volume) | 883mVrms | 882mVrms |
Noise level (with signal, A-weighted) | <112uVrms | <118uVrms |
Noise level (with signal, 20Hz to 20kHz) | <240uVrms | <240uVrms |
Noise level (no signal, A-weighted) | <103uVrms | <103uVrms |
Noise level (no signal, 20Hz to 20kHz) | <156uVrms | <156uVrms |
Output impedance (pre-out) | 101 ohms | 101 ohms |
Signal-to-noise ratio (80W, A-weighted, 2Vrms in) | 107.7dB | 107.0dB |
Signal-to-noise ratio (80W, 20Hz to 20kHz, 2Vrms in) | 104.2dB | 103.4dB |
Signal-to-noise ratio (80W, A-weighted, max volume) | 108.4dB | 108.4dB |
Dynamic range (80W, A-weighted, digital 24/96) | 107.5dB | 106.8dB |
Dynamic range (80W A-weighted, digital 16/44.1) | 95.5dB | 95.5dB |
THD ratio (unweighted) | <0.0063% | <0.0072% |
THD ratio (unweighted, digital 24/96) | <0.0061% | <0.0077% |
THD ratio (unweighted, digital 16/44.1) | <0.0065% | <0.0078% |
THD+N ratio (A-weighted) | <0.007% | <0.008% |
THD+N ratio (A-weighted, digital 24/96) | <0.007% | <0.0088% |
THD+N ratio (A-weighted, digital 16/44.1) | <0.0076% | <0.009% |
THD+N ratio (unweighted) | <0.007% | <0.008% |
Minimum observed line AC voltage | 124VAC | 124VAC |
For the continuous dynamic power test, the MaiA DS3 was able to sustain 141W into 4 ohms (~2% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (14.1W) for 5s, for 5 continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the MaiA DS3 was only slightly warm to the touch.
Our primary measurements revealed the following using the phono-level input, MM configuration (unless specified, assume a 1kHz 5mVrms sinewave input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -58.5dB | -57.7dB |
DC offset | <10mV | <10mV |
Gain (default phono preamplifier) | 45dB | 44.9dB |
IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-80dB | <-80dB |
IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-59dB | <-59dB |
Input impedance | 51.3k ohms | 52.6k ohms |
Input sensitivity (to max power with max volume) | 2.5mVrms | 2.5mVrms |
Noise level (with signal, A-weighted) | <360uVrms | <330uVrms |
Noise level (with signal, 20Hz to 20kHz) | <800uVrms | <700uVrms |
Noise level (no signal, A-weighted) | <400uVrms | <350uVrms |
Noise level (no signal, 20Hz to 20kHz) | <800uVrms | <700uVrms |
Overload margin (relative 5mVrms input, 1kHz) | 19.1dB | 19.2dB |
Signal-to-noise ratio (80W, A-weighted, 5mVrms in) | 87.3dB | 87.2dB |
Signal-to-noise ratio (80W, 20Hz to 20kHz, 5mVrms in) | 82.0dB | 81.5dB |
Signal-to-noise ratio (80W, A-weighted, max volume) | 81.5dB | 81.0dB |
THD (unweighted) | <0.0068% | <0.0081% |
THD+N (A-weighted) | <0.0085% | <0.0099% |
THD+N (unweighted) | <0.012% | <0.012% |
Our primary measurements revealed the following using the phono-level input, MC configuration (unless specified, assume a 1kHz 0.5mVrms sinewave input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -56.5dB | -48.4dB |
DC offset | <10mV | <10mV |
Gain (default phono preamplifier) | 63.3dB | 63.3dB |
IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-72dB | <-72dB |
IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-72dB | <-72dB |
Input impedance | 140 ohms | 141 ohms |
Input sensitivity (to max power with max volume) | 0.305mVrms | 0.305mVrms |
Noise level (with signal, A-weighted) | <4mVrms | <3.6mVrms |
Noise level (with signal, 20Hz to 20kHz) | <8mVrms | <7mVrms |
Noise level (no signal, A-weighted) | <4.7mVrms | <4.3mVrms |
Noise level (no signal, 20Hz to 20kHz) | <9mVrms | <8mVrms |
Overload margin (relative 0.5mVrms input, 1kHz) | 20.7dB | 20.8dB |
Signal-to-noise ratio (80, A-weighted, 0.5mVrms in) | 65.8dB | 65.6dB |
Signal-to-noise ratio (80W, 20Hz to 20kHz, 0.5mVrms in) | 60.7dB | 61.2dB |
Signal-to-noise ratio (80W, A-weighted, max volume) | 61.6dB | 61.2dB |
THD (unweighted) | <0.008% | <0.01% |
THD+N (A-weighted) | <0.045% | <0.045% |
THD+N (unweighted) | <0.09% | <0.09% |
Our primary measurements revealed the following using the analog input at the headphone output (unless specified, assume a 1kHz sinewave, 2Vrms output, 300 ohms loading, 10Hz to 22.4kHz bandwidth, and the +6dB gain switch disengaged):
Parameter | Left channel | Right channel |
Maximum output power into 600 ohms (1% THD+N, unweighted) | 94mW | 94mW |
Maximum output power into 300 ohms (1% THD+N, unweighted) | 169mW | 169mW |
Maximum output power into 32 ohms (1% THD+N, unweighted) | 401mW | 405mW |
Gain | 18.6/24.6dB | 18.6/24.7dB |
Output impedance | 34.5 ohms | 34.5 ohms |
Noise level (no signal, A-weighted) | <16uVrms | <16uVrms |
Noise level (no signal, 20Hz to 20kHz) | <23uVrms | <23uVrms |
Signal-to-noise ratio (max output, A-weighted, 2Vrms in) | 112.2dB | 111.5dB |
Signal-to-noise ratio (max output, 20Hz to 20kHz, 2Vrms in) | 109.5dB | 108.8dB |
THD ratio (unweighted) | <0.00077% | <0.0069% |
THD+N ratio (A-weighted) | <0.0011% | <0.0011% |
THD+N ratio (unweighted) | <0.0014% | <0.0014% |
Frequency response (8-ohm loading, line-level input)
In our measured frequency response (relative to 1kHz) chart above, the MaiA DS3 is essentially flat within the audioband (-0.09dB at 20Hz, +0.28dB at 20kHz). The rise in relative response at high frequencies is due to the class-D amplifier’s poor damping factor (i.e., high output impedance) at high frequencies. When the frequency response into 4 ohms is plotted (see RMS level v frequency v load graphs below), we find a dip in response at high frequencies. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched. Because the MaiA DS3 exhibited poor channel tracking, we’ve also plotted . . .
. . . RMS level vs frequency, to show the channel-to-channel deviations. In the chart above, we can see that the right channel is roughly 0.8dB lower in output than the left channel. This is due to the deviations inherent to the potentiometer used to control the volume.
Phase response (line-level input)
Above is the phase response plot from 20Hz to 20kHz for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The MaiA DS3 does not invert polarity. Here we find a worst case of about +30 degrees at 20Hz and 20kHz.
Frequency response (line-level analog input, subwoofer line-level output)
In our measured frequency response of the line-level subwoofer output shown above, the MaiA DS3 is at 0dB at 20Hz and -0.5dB at 20kHz. As a result, it is clear that the sub-out does not offer any built-in low-pass filtering.
Frequency response vs. input type (8-ohm loading, left channel only)
The chart above shows the MaiA DS3’s frequency response (relative to 1kHz) as a function of input type measured across the speaker outputs at 10W into 8 ohms. The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 10Hz to 22kHz using the coaxial digital input, and the purple trace is for a 24/96 dithered digital input signal from 10Hz to 48kHz, while the pink trace is for a 24/192 dithered digital input signal from 10Hz to 96kHz. The green trace is the same analog input frequency response seen above. The 16/44.1 data exhibits brickwall-type filtering, with a -3dB at 21.2kHz. The 24/96 and 24/192 kHz data were nearly identical, yielding -3dB points at 45.3kHz and 46.5kHz respectively. The analog input data yields a -3dB point at 58kHz.
Frequency response (8-ohm loading, MM phono input)
The chart above shows the frequency response (relative to 1kHz) for the MM phono input. We see maximum deviations within about ±0.25dB from 20Hz to 20kHz for the left channel, and about ±0.5dB for the right channel. What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (i.e., zero deviation would yield a flat line at 0dB).
Phase response (MM input)
Above is the phase response plot from 20Hz to 20kHz for the MM phono input, measured across the speaker outputs at 10W into 8 ohms. The MaiA DS3 does not invert polarity. For the phono input, since the RIAA equalization curve must be implemented, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case of about -60 degrees at 200Hz and 5kHz.
Frequency response (8-ohm loading, MC phono input)
The chart above shows the frequency response (relative to 1kHz) for the MC phono input. What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (i.e., zero deviation would yield a flat line at 0dB). We see maximum deviations within about ±0.5dB from 20Hz to 20kHz for both channels, although the left channel is much flatter than the right channel between 100Hz and 10kHz.
Phase response (MC input)
Above is the phase response plot from 20Hz to 20kHz for the MC phono input, measured across the speaker outputs at 10W into 8 ohms. The MaiA DS3 does not invert polarity. The response is essentially identical to the phase response for the MM input above.
Digital linearity (16/44.1 and 24/96 data)
The chart above shows the results of a linearity test for the coaxial digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the fixed line-level pre-outs of the MaiA DS3 for a 1.36Vrms (at 0dBFS) output signal. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response would be a straight flat line at 0dB. Both data were essentially perfect as of -100dBFS down to 0dBFS. At -120dBFS, the 16/44.1 data were about +2dB (left/right channels) above reference, while the 24/96 data were still at the reference 0dB level. This is a good linearity test result.
Impulse response (24/44.1 data)
The graph above shows the impulse response for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s) for one sample period then back to digital silence, measured at the fixed line-level pre-outs of MaiA DS3. We can see that the MaiA DS3 utilizes a typical symmetrical sinc function reconstruction filter.
J-Test (coaxial)
The chart above shows the results of the J-Test test for the coaxial digital input measured at the line level pre-outs of the MaiA DS3. J-Test was developed by Julian Dunn in the 1990s. It is a test signal—specifically, a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (i.e., 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sinewave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (e.g., 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA and below. The test file can also be used in conjunction with artificially injected sinewave jitter by the Audio Precision, to show how well the DAC rejects jitter.
The coaxial input exhibits low-level peaks in the audioband, as high as -130dBrA. This is an average J-Test result, indicating that the MaiA DS3 DAC may be susceptible to jitter.
J-Test (optical)
The chart above shows the results of the J-Test test for the optical digital input measured at the fixed line-level pre-outs of the MaiA DS3. It is essentially the same result as with the coax input shown above.
J-Test with 100ns of injected jitter (coaxial)
Both the coaxial and optical inputs were also tested for jitter immunity by injecting 100ns of artificial sinewave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved poor at the 100ns level, with visible sidebands at -100dBrA. The optical input jitter result was very similar to the coaxial input result.
J-Test with 500ns of injected jitter (coaxial)
Both the coaxial and optical inputs were also tested for jitter immunity by injecting 500ns of artificial sinewave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved poor, with visible sidebands at -85dBrA. The MaiA DS3DAC did lose sync with the signal when jitter was increased beyond 500ns. The optical input jitter result was very similar to the coaxial input result.
Wideband FFT spectrum of white noise and 19.1kHz sinewave tone (coaxial input)
The plot above shows a fast Fourier transform (FFT) of the MaiA DS3’s fixed line-level pre-outs with white noise at -4 dBFS (blue/red) and a 19.1 kHz sinewave (purple/green) at 0dBFS fed to the coaxial digital input, sampled at 16/44.1. The sharp roll-off above 20kHz in the white-noise spectrum shows the implementation of a brick-wall type reconstruction filter. There are no aliased image peaks in the audioband above the noise floor at -135dBrA. The main 25kHz alias peak is highly suppressed at -105dBrA. The second, third, and fourth distortion harmonics (38.2, 57.3, 76.4kHz) of the 19.1kHz tone are between -90dBrA and -100dBrA.
RMS level vs. frequency vs. load impedance (1W, left channel only)
The chart above shows RMS level (relative to 0dBrA, which is 1W into 8 ohms, or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .
. . . is the same but zoomed in to highlight differences. Here we can see a significant maximum deviation at 20kHz of about 2.3dB from 4 ohms to no load, which is an indication of a very low damping factor at high frequencies, or high output impedance. The deviation in RMS level below 2kHz from no load to 4 ohms is much less, at about 0.2dB. The variation in RMS level when a real speaker was used is also significant, deviating by about 0.3-0.4dB, with the lowest response at 200Hz, and the highest at 5kHz.
THD ratio (unweighted) vs. frequency vs. output power
The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sinewave stimulus at the analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 55W. The power was varied using the volume control. At 1W, THD ratios ranged from 0.007% at 20Hz, down to 0.002% at 6kHz. At 10W, THD ratios ranged from 0.02% at 20Hz, down to 0.005% at 2-3kHz. The 55W THD values are higher and range from 0.05% at 20Hz, down to 0.015% at 2kHz, then up to 0.03% at 6kHz. These data corroborate Pro-Ject’s claim of less than 0.01% THD at 10W at 1kHz.
THD ratio (unweighted) vs. frequency at 10W (MM/MC input)
The chart above shows THD ratios as a function of frequency plots for the MM and MC phono input configurations measured across an 8-ohm load at 10W. The input sweep is EQ’d with an inverted RIAA curve. The THD values for the MM configuration vary from around 0.02% (20Hz) down to just beow 0.01% at 1-2kHz, the back up to 0.02% at 6kHz. The THD values for the MC configuration vary from around 0.08% (20Hz) down to as low as 0.003% (left channel) at 3kHz, then up to 0.01% at 6kHz.
THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD ratios measured at the output of the MaiA DS3 as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Both data sets track fairly closely, with the 8-ohm data outperforming the 4-ohm data by about 5dB. The 8-ohm data ranges from around 0.002% at 1W and below, up to 0.015% at the “knee” around 70W, then up to the 1% THD mark at the rated 80W. With a 4-ohm load, the “knee” occurs at about 120W, and the 1% THD value was reached at 144W.
THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms
The chart above shows THD+N ratios measured at the output of the MaiA DS3 as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Overall, THD+N values for both loads were similar, ranging from 0.02%, down to just below 0.01%, with the 8-ohm data outperforming the 4-ohm data by about 2-5dB.
THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)
The chart above shows THD ratios measured at the output of the MaiA DS3 as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yielded 10W at the output into 8 ohms (and roughly 20W into 4 ohms, and 40W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find the 8-ohm trace ranging from 0.01% at 20Hz down to 0.003% at 2kHz, and outperforming the 4-ohm trace by about 5dB (except at 6kHz, where both data sets yielded THD ratios of 0.01%). THD values with a 2-ohm load were much higher, ranging from 0.05% at 20Hz, down to 0.03% at 400Hz, then up to 0.1% at 6kHz. Nonetheless, these data show that the MaiA DS3 is stable into 2-ohm loads.
THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows THD ratios measured at the output of the MaiA DS3 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). At lower frequencies, the two-way speaker yielded the highest THD ratios, as high as 0.15% at 20Hz, but as low as 0.001% at 3-4kHz. The three-way speaker ranged from a high of 0.015% at 20Hz, down to 0.0025% at 2kHz, and up to 0.015% at 6kHz. Generally, THD ratios were higher with real speakers compared to the 8-ohm dummy resistive load.
IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows intermodulation distortion (IMD) ratios measured at the output of the MaiA DS3 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method was used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). The results for the dummy load were fairly consistent, hovering between 0.003% and 0.005% from 2.5kHz to 20kHz. We find that the two-way speaker yielded IMD ratios 15dB higher than the dummy load above 10kHz, reaching 0.04% at 20kHz, compared to 0.005% for the dummy load. The three-way speaker yielded IMD ratios roughly 15dB higher than the dummy load across the swepted frequencies.
IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)
The chart above shows IMD ratios measured at the output of the MaiA DS3 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method was used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are similar, with the two-way speaker and dummy load consistently yielding 0.01% IMD, and the three-way speaker reaching 0.02% from 100Hz to 250Hz.
FFT spectrum – 1kHz (line-level input)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s second harmonic (2kHz) dominates at around -85dBrA, or 0.006%. The subsequent signal harmonics are around or below -100dBrA, or 0.001%. There are clearly visible power-supply-related noise peaks at even harmonics (120Hz, 240Hz, 360Hz, etc.) on the left side of the main 1kHz peak, at -95dBrA, or 0.002%, down to -120dBrA, or 0.0001%. There is also a rise in the noise above 20kHz, characteristic of digital amplifiers.
FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 16/44.1. The signal and noise-related harmonics are very similar to the FFT above for the analog input.
FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 24/96. The signal- and noise-related harmonics are very similar to the FFT above for the analog input.
FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)
Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and signal harmonics from the right channel at -90dBrA, or 0.003%, and below. The noise floor is also elevated, as high as -110dBrA.
FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)
Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and signal harmonics from the right channel at -90dBrA, or 0.003%, and below. The noise floor is also elevated, as high as -110dBrA.
FFT spectrum – 1kHz (MM phono input)
Shown above is the FFT for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the MM phono input. We see that the signal’s second harmonic (2kHz) dominates at around -85dBrA, or 0.006%. The subsequent signal harmonics are around or below -100dBrA, or 0.001%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, at -90dBrA, or 0.003%, down to -110dBrA, or 0.0003%.
FFT spectrum – 1kHz (MC phono input)
Shown above is the FFT for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the MC phono input. We see that the signal’s second harmonic (2kHz) dominates at around -90/85dBrA (left/right channels), or 0.003/0.006%. Most of the subsequent signal harmonics are buried beneath the noise-floor, which ranges from -100dBrA to -120dBrA from 2kHz to 20kHz. There are three clearly visible power-supply related noise peaks at 60Hz, 120Hz and 180Hz, on the left side of the main 1kHz peak, at -70dBrA, or 0.03%, and -85dBrA, or 0.006%.
FFT spectrum – 50Hz (line-level input)
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s second harmonic (100Hz) dominates at around -75dBrA, or 0.02%. The subsequent signal harmonics are around or below -100dBrA, or 0.001%. There are clearly visible power-supply-related noise peaks at even harmonics (120Hz, 240Hz, 360Hz, etc.) at -95dBrA, or 0.002%, down to -120dBrA, or 0.0001%.
FFT spectrum – 50Hz (MM phono input)
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the MM phono input. The X axis is zoomed in from 40 Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s second harmonic (100Hz) dominates at around -75dBrA, or 0.02%. The subsequent signal harmonics are around or below -100dBrA, or 0.001%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) at -90dBrA, or 0.003%, down to -110dBrA, or 0.0003%.
FFT spectrum – 50Hz (MC phono input)
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the MC phono input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s second harmonic (100Hz) dominates at around -80dBrA, or 0.01%. Most of the subsequent signal harmonics are buried beneath the noise-floor, which ranges from -90dBrA to -110dBrA from 50Hz to 1kHz. There are three clearly visible power-supply-related noise peaks at 60Hz, 120Hz, and 180Hz at -70dBrA, or 0.03%, and -85dBrA, or 0.006%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -90dBrA or 0.003%. The third-order modulation products, at 17kHz and 20kHz, are at around the same level.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 16/44.1)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 16/44.1. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -90dBrA, or 0.003%. The third-order modulation products, at 17kHz and 20kHz, are at around the same level.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 24/96)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 24/96. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -90dBrA, or 0.003%. The third-order modulation products, at 17kHz and 20kHz, are at around the same level.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MM phono input)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the MM phono input. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -70dBrA, or 0.03%. The third-order modulation products, at 17kHz and 20kHz, are at around the same level.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MC phono input)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the MC phono input. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -90dBrA, or 0.003%. The third-order modulation products, at 17kHz and 20kHz, are at around the same level.
Square-wave response (10kHz)
Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the MaiA DS3’s slew-rate performance. Rather, it should be seen as a qualitative representation of the MaiA DS3’s average bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (e.g., 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. Here we can see the 600kHz switching oscillator frequency used in the digital amplifier section visibly modulating the waveform.
Square-wave response (10kHz, restricted 250kHz bandwidth)
Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms, this time with a 250kHz input bandwidth on the analyzer to filter out the 600kHz switching frequency. We see more evidence here, in the overshoot and soft corners of the squarewave, of the MaiA DS3’s average bandwidth.
FFT spectrum (1MHz bandwidth)
The MaiA DS3’s class-D amplifier relies on a switching oscillator to convert the input signal to a pulse-width-modulated (PWM) squarewave (on/off) signal before sending the signal through a low-pass filter to generate an output signal. The MaiA DS3 oscillator switches at a rate of about 600kHz, and this graph plots a wide bandwidth FFT spectrum of the amplifier’s output at 10W into 8 ohms as it’s fed a 1kHz sinewave. We can see that the 600kHz peak is quite evident, and at -40dBrA. There is also a peak at 1.2MHz (the second harmonic of the 600kHz peak), at -80dBrA. Those peaks—the fundamental and its harmonic—are direct results of the switching oscillators in the MaiA DS3’s amp modules. The noise around those very-high-frequency signals are in the signal, but all that noise is far above the audioband—and therefore inaudible—and so high in frequency that any loudspeaker the amplifier is driving should filter it all out anyway.
Damping factor vs. frequency (20Hz to 20kHz)
The final graph above is the damping factor as a function of frequency. Both channels show a relatively constant damping factor from 20Hz to 2kHz, at around 86/80 (left/right). Above 2kHz, we see a steep decline in damping factor, as low as 10 at 20kHz, which is typical of this type of digital-amplifier technology.
Diego Estan
Electronics Measurement Specialist
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