Link: reviewed by Doug Schneider on SoundStage! Hi-Fi on April 15, 2021
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The LINEb was conditioned for 30 minutes at 2Vrms at the output before any measurements were taken. All measurements were taken with both channels driven.
The LINEb offers two sets of line-level unbalanced (RCA) inputs, four sets of line-level balanced (XLR) inputs, and two sets of balanced (XLR) outputs. The volume control is implemented using relays and a discrete high-precision resistor ladder. The RCA inputs yield 6dB more gain than the XLR inputs, with a range from –51.4dB (volume position 1 on the display) to +11.8dB (volume position 64). The XLR inputs range from -57.4dB to +5.8dB. The volume control offers 1dB steps from 1 to 56, 0.5dB from 56 to 57, 1dB from 58 to 61, 1.5dB from 61 to 63, and 2dB from 63 to 64. Unity gain (+0.1dB) is achieved at position 60 for the XLR inputs, 54 (-0.1dB) for the RCA inputs. Channel volume tracking is superb (see table below).
There is an Audio Gnd switch on the LINEb back panel. Presumably, this switch disconnects audio ground from chassis/earth ground. I found no differences in noise performance with the switch in the off or on position. It was left on for the measurements.
I found effectively no difference in THD+N values between the RCA and XLR inputs for the same output voltage. I attempted to optimize the volume position to achieve the best signal-to-noise (SNR) and THD+N measurements; however, I found only small differences with the volume at various positions (for the same output voltage). Most measurements were made with the volume set to unity gain (60) using the XLR inputs.
Volume-control accuracy (measured at preamp outputs): left-right channel tracking
Volume position | Channel deviation |
1 | 0.009dB |
5 | 0.009dB |
10 | 0.008dB |
20 | 0.009dB |
40 | 0.023dB |
50 | 0.026dB |
60 | 0.025dB |
64 | 0.024dB |
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Karan Acoustics for the LINEb compared directly against our own. The published specifications are sourced from Karan Acoustic’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 90kHz, and the worst-case measured result between the left and right channels.
Parameter | Manufacturer | SoundStage! Lab |
Input impedance | 30k ohms | 57k ohms* |
Output impedance | 90 ohms | 180 ohms* |
Maximum output level (1% THD+N, 600 ohms) | 18Vrms | 15.5Vrms |
Maximum output level (1% THD+N, 200k ohms) | 18Vrms | 20.6Vrms |
Gain | 6dB | 5.8dB |
Frequency response (20Hz-20kHz) | ± 0dB | ± 0dB |
Frequency response (1.5Hz-3MHz) | -3dB | -0.2dB at 200kHz |
THD (20Hz-20kHz, 2Vrms, 200k ohms) | <0.003% | <0.0002% |
IMD ratio (18kHz and 19kHz stimulus tones, 2Vrms, 200k ohms) | <0.003% | <0.00023% |
SNR (2Vrms output, unweighted, 200k ohms) | >120dB | 109dB |
SNR (18Vrms output, unweighted, 200k ohms) | >120dB | 128dB |
* The discrepancy in balanced input/output impedances may be due to Karan specifying this value for the inverting and noninverting pins separately. Our measurement considers both inputs/outputs on the balanced connector together. Treated separately, our measurement would be halved, or, respectively, 28.5k ohms and 90 ohms for the input and output impedances.
Our primary measurements revealed the following using the balanced line-level inputs (unless specified, assume a 1kHz sine wave, 2Vrms output into 200k ohms load, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -108dB | -109dB |
DC offset | <-0.7mV | <-0.4mV |
Gain (default) | 5.84dB | 5.82dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-113dB | <-115dB |
Input impedance | 57.6k ohms | 57.3k ohms |
Maximum output voltage (at clipping 1% THD+N) | 20.6Vrms | 20.6Vrms |
Maximum output voltage (at clipping 1% THD+N into 600 ohms) | 15.5Vrms | 15.5Vrms |
Noise level (A-weighted) | <5.8uVrms | <5.4uVrms |
Noise level (unweighted) | <19uVrms | <15uVrms |
Output impedance | 179.7 ohms | 179.9 ohms |
Signal-to-noise ratio (A-weighted) | 111.1dB | 111.6dB |
Signal-to-noise ratio (unweighted, 20Hz to 20kHz) | 109.1dB | 109.8dB |
THD (unweighted) | <0.000064% | <0.000060% |
THD+N (A-weighted) | <0.00028% | <0.00027% |
THD+N (unweighted) | <0.00093% | <0.00072% |
Frequency response
In our measured frequency-response chart above, the LINEb is perfectly flat within the audioband (20Hz to 20kHz) and beyond. These data partially corroborate Karan Acoustics’ claim of 20Hz to 20kHz +/-0dB, 1.5Hz to 3MHz (-3dB). However, since the Audio Precision can only sweep to just past 200kHz, we cannot verify the -3dB at 3MHz claim portion. The LINEb is at 0dB at 5Hz, and at about -0.2dB at 200kHz. To state that the LINEb is a high-bandwidth audio device would be an understatement.
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 overlap perfectly, indicating that the two channels are ideally matched.
Phase response
Above is the phase-response chart from 20Hz to 20kHz. The LINEb does not invert polarity, and the plot shows essentially no phase shift within the audioband.
THD ratio (unweighted) vs. frequency
The chart above shows THD ratios at the output as a function of frequency (20Hz to 20kHz) for a sine-wave input stimulus. The blue and red plots are for left and right channels into 200k ohms, while purple/green (L/R) are into 600 ohms. THD values are very low, about 0.00004% into 200k ohms from 20Hz to 1kHz, and, most impressively, even lower at about 0.00003% into a 600-ohm load. There is a rise in THD values above 1kHz, where at 20kHz, the 600-ohm data are about 0.0003%, and the 200k-ohm data are lower at about 0.0002%, which are still extremely low figures.
THD ratio (unweighted) vs. output voltage at 1kHz
The chart above shows THD ratios measured at the output of the LINEb as a function of output voltage into 200k ohms with a 1kHz input sine wave. At the 10mVrms level, THD values measured around 0.007%, dipping down to around 0.00003% at 3Vrms. The “knee” occurs at around 18Vrms, hitting the 1% THD just past 20Vrms. It’s important to note here that the LINEb’s extraordinarily low THD values are approaching the limits of the Audio Precision analyzer, which, when measured in loopback mode (generator feeding analyzer) measures about 50% lower than the LINEb (at 3Vrms), at about 0.000015%. It’s also important to mention that anything above 2-4Vrms is not typically required to drive most power amps into full power.
THD+N ratio (unweighted) vs. output voltage at 1kHz
The chart above shows THD+N ratios measured at the output the LINEb as a function of output voltage into 200k ohms with a 1kHz input sine wave. At the 10mVrms level, THD+N values measured around 0.1-0.2%, dipping down to around 0.0002% at 10Vrms.
FFT spectrum – 1kHz
Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output into a 200k-ohm load. The red is the right channel, the blue the left. We see that the signal’s second harmonic, at 2kHz, is at a vanishingly low -140dBrA, or 0.00001%, while the third harmonic, at 3kHz, is just slightly above -140dBrA. Below 1kHz, we see some noise artifacts, with the 60Hz peak due to power supply-noise barely perceptible on the left channel below -140dBrA, and the 180Hz (third harmonic) peak just above -140dBrA. The right channel does not appear to show any noise peaks above the very low -150dBrA noise floor.
FFT spectrum – 50Hz
Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the output into a 200k-ohm load. 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. Here again, there are barely any noticeable peaks. We find the third harmonic of the signal (150Hz) just peaking above the -150dBrA noise floor, or 0.000003%, and the left channel showing the third-harmonic noise peak (180Hz) just above -140dBrA, or 0.00001%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output into a 200k-ohm load. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 2Vrms (0dBrA) at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -125dBrA, or 0.00006%, while the third-order modulation products, at 17kHz and 20kHz are at -130dBrA and -125dBrA, or 0.00003% and 0.00006%, respectively. These extraordinarily low harmonic peaks are reflected in the IMD values in our primary table of -113/-115dB, which represent the sum of the second- and third-order intermodulation product peaks.
Square-wave response (10kHz)
Shown above is the 10kHz square-wave response at the output into 200k ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this chart should not be used to infer or extrapolate the LINEb’s slew-rate performance. Rather, it should be seen as a qualitative representation of its very high bandwidth. An ideal square wave can be represented as the sum of a sine wave 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 square-wave representation. As mentioned above, the LINEb is a very high-bandwidth component. Correspondingly, the LINEb’s reproduction of the 10kHz square wave is squeaky clean, with very sharp edges devoid of undershoot or overshoot.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Matt Bonaccio on SoundStage! Hi-Fi on January 1, 2024
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The Darlington Labs MP-7 and SU-7 were conditioned for 30 minutes at 1Vrms at the output before any measurements were taken.
The MP-7 and SU-7 each offer one pair of unbalanced RCA inputs and outputs. The MP-7 on its own is designed for a moving-magnet (MM) cartridge with a set gain of 40dB, 47k ohms input impedance, and 100pF of input capacitance. The SU-7 is a step-up amplifier designed to be used in series with and ahead of the MP-7 for low-output moving-coil (MC) cartridges. The SU-7 offers four gain settings: 12, 18, 23, 26dB. It also offers seven input-impedance settings: 47, 100, 220, 470, 1k, 5k, 47k ohms.
Unless otherwise specified, the MP-7 was used on its own for the MM use case, and the SU-7 was used ahead of and in series with the MP-7 with the gain set to 23dB (63dB total) and input impedance set to 220 ohms for the MC use case. Using the default settings above, to achieve the reference output voltage of 1Vrms at 1 kHz, 11mVrms was required for the MM configuration, and 0.9mVrms for the MC configuration.
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Darlington Labs for the MP-7 and SU-7 compared directly against our own. The published specifications are sourced from Darlington Labs’ 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 set at its maximum (DC to 1MHz), assume, unless otherwise stated, 1Vrms output into 100k ohms and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels. For the MC gain setting measurements, the input impedance was set to 47k ohms. The MP-7 and SU-7 specifications were measured separately.
Parameter | Manufacturer | SoundStage! Lab |
MP-7 | ||
Input impedance | 47k ohms | 52.6k ohms |
Frequency response (20Hz-20kHz) | ±0.2dB | +0.5/-0.26dB (30Hz/220Hz) |
THD (1kHz, 500mV out) | <0.08% | <0.056% |
Distortion (1kHz, 500mV out, 3rd harmonic and higher) | <0.01% | <0.0006% |
Signal-to-noise ratio (5mV in, 1kHz, A-wgt) | >78dB | 77.5/75.9dB (L/R) |
Input overload (1kHz, 2% THD) | 140mVrms | 140mVrms |
Maximum output (3% THD) | 17Vrms | 17Vrms |
SU-7 | ||
Gain | 12/18/23/26dB | 11.9/16.7/22.3/29.1dB |
Input impedance | 47/100/220/470/1k/5k/47k ohms | 45/97/212/537/0.95k/4.9k/50.9k ohms |
Frequency response (20Hz-20kHz) | ±0.1dB | -0.01/-0.04dB (20Hz/20kHz) |
THD (1kHz, 5mV out, 23dB gain) | <0.01% | <0.006% |
Signal-to-noise ratio (0.4mV in, 1kHz, A-wgt) | >73dB | 70dB |
Input overload (1kHz) | 140mV | 800mV |
Maximum output | 8Vrms | 9.4Vrms |
Our primary measurements revealed the following using the MM configuration (unless specified, assume a 1kHz sinewave, 1Vrms output into a 100k ohms load, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -73dB | -51dB |
DC offset | <-12mV | <-11mV |
Gain (default) | 39.3dB | 39.3dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-26dB | <-25dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-56dB | <-56dB |
Input impedance | 52.7k ohms | 51.9k ohms |
Maximum output voltage (at clipping 1% THD+N) | 9.1Vrms | 9.1Vrms |
Noise level (with signal, A-weighted) | <55uVrms | <70uVrms |
Noise level (with signal, 20Hz-20kHz) | <260uVrms | <360uVrms |
Output impedance | 271 ohms | 233 ohms |
Overload margin (relative 5mVrms input, 1kHz) | 26dB | 26dB |
Overload margin (relative 5mVrms input, 20Hz) | 4.1dB | 4.1dB |
Overload margin (relative 5mVrms input, 20kHz) | 36.1dB | 36.1dB |
Signal-to-noise ratio (A-weighted) | 83.7dB | 82.3dB |
Signal-to-noise ratio (20Hz-20kHz) | 72.7dB | 69.2dB |
THD (unweighted) | <0.112% | <0.108% |
THD+N (A-weighted) | <0.129% | <0.125% |
THD+N (unweighted) | <0.115% | <0.115% |
Our primary measurements revealed the following using the MC configuration (unless specified, assume a 1kHz sinewave, 1Vrms output into a 100k ohms load, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -68.4dB | -51.3dB |
DC offset | <-12mV | <-12mV |
Gain (default SU-7) | 22.3dB | 22.3dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-26dB | <-26dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-56dB | <-56dB |
Input impedance | 212 | 214 |
Maximum output voltage (at clipping 1% THD+N, SU-7) | 9.4Vrms | 9.4Vrms |
Noise level (with signal, A-weighted) | <126uVrms | <122uVrms |
Noise level (with signal, 20Hz-20kHz) | <1.7uVrms | <0.5uVrms |
Output impedance (SU-7) | 95 ohms | 94 ohms |
Overload margin (relative 0.5mVrms input, 1kHz) | 24.1dB | 24.1dB |
Overload margin (relative 0.5mVrms input, 20Hz) | 2.92dB | 2.92dB |
Overload margin (relative 0.5mVrms input, 20kHz) | 35dB | 35dB |
Signal-to-noise ratio (A-weighted) | 77.4dB | 77.6dB |
Signal-to-noise ratio (20Hz-20kHz) | 55.2dB | 65.6dB |
THD (unweighted) | <0.109% | <0.105% |
THD+N (A-weighted) | <0.127% | <0.122% |
THD+N (unweighted) | <0.20% | <0.12% |
*SU-7 measured on its own without MP-7
Frequency response - MM input
Above are our measured frequency-response plots (relative to 1kHz) for the MM configuration. An inverse RIAA EQ is applied to the input sweep, so that if a device were to track the RIAA curve perfectly, a flat line would emerge. The MP-7 is within +/-0.5dB or so of flat from 20Hz to 20kHz. The worst-case deviation can be seen at 30Hz, with a +0.5dB rise. At 20kHz, the response is at -0.1dB. These data do not quite corroborate Darlington Labs’ claim of 20Hz to 20kHz +/-0.2dB. The worst-case channel-to-channel deviation is roughly 0.1dB, from 100Hz to 300Hz and 3kHz to 6kHz. In the graph above and some of the graphs below, we see two visible traces: the left channel (blue or purple) and the right channel (red or green). On other graphs, only one trace may be visible. When one trace is visible it is because the left and right channels are tracking extremely closely, so they do not to show a difference with the chosen axis scales.
Frequency response - MC input
In our measured frequency-response plot above for the MC configuration, the MP-7 and SU-7 yields virtually the same results as with the MM configuration (MP-7 on its own) above. Of note is that only the MP-7 implements the RIAA equalization curve.
Phase response - MM and MC inputs
Above is the phase response for the MM and MC configuration, from 20Hz to 20kHz. The MP-7 and SU-7 do not invert polarity. Since phono preamplifiers must implement the RIAA equalization curve, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst-case -60 degrees around 200Hz and -90 degrees at 20kHz.
THD ratio (unweighted) vs. frequency - MM and MC inputs
The chart above shows THD ratios as a function of frequency, where the input sweep is EQ’d with an inverted RIAA curve. The output voltage is maintained at the refrence 1Vrms. The red/blue (L/R) traces represent the MM configuration (MP-7), and purple/green for the MC configuration (SU-7 + MP-7). THD ratios are essentially identical for both MM and MC configurations, ranging from 0.15% from 20Hz to 200Hz, down to 0.1% at 1-2kHz, then up to 0.3% at 20kHz.
THD ratio (unweighted) vs. output voltage at 1kHz - MM and MC inputs
The chart above shows THD ratios as a function of output voltage. The red/blue (L/R) traces represent the MM configuration, and purple/green the MC configuration. THD ratios are essentially identical for both MM and MC configurations, ranging from 0.01% from 50mVrms to 100mVrms, then a steady rise to just past 2% at roughly 15Vrms. The 1% THD mark was reached at 9.1Vrms. At an output of 0.5Vrms, where the input for the MM configuartion is very close to the standard 5mVrms (and 0.5mVrms for the MC configuratiuon), THD ratios are 0.05%.
THD+N ratio (unweighted) vs. output voltage at 1kHz - MM and MC inputs
The chart above shows THD+N ratios as a function of output voltage. The red/blue (L/R) traces represent the MM configuration, and purple/green the MC configuration. THD+N ratios are essentially identical for both MM and MC configurations above 2Vrms, where THD dominates, ranging from 0.2% up to 2% at 15Vrms. At low output voltages (50mVrms to 1Vrms), where noise is more dominant, the left channel for the MC configuration exhibited higher THD+N ratios, ranging from 3.5% at 50mVrms down to 0.2% at 1Vrms. The right-channel MC configuration THD+N ratios ranged from 1% at 50mVrms down to 0.1% at 1Vrms. The left and right channels for the MM configuration THD+N ratios ranged from 0.5% at 50mVrms down to 0.1% at 1Vrms.
THD+N ratio (A-weighted) vs. output voltage at 1kHz - MM and MC inputs
The chart above shows THD+N ratios (A-weighted) as a function of output voltage. The red/blue (L/R) traces represent the MM configuration, and purple/green the MC configuration. THD+N ratios are essentially identical for both MM and MC configurations above 0.5Vrms, where THD dominates, ranging from 0.06% up to 2% at 15Vrms. At low output voltages (50mVrms to 0.5Vrms), where noise is more dominant, the MC configuration exhibited higher THD+N ratios, ranging from 0.2% at 50mVrms down to 0.05% at 1Vrms. The MM configuration THD+N ratios ranged from 0.1% at 50mVrms down to 0.04% at 0.2-0.3Vrms.
FFT spectrum, 1kHz - MM input
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sinewave stimulus for the MM configuration, which results in the reference voltage of 1Vrms (0dBrA) at the output. Signal harmonics are dominated by the second harmonic (2kHz) at a high -60dBrA, or 0.1%, while the third harmonic (3kHz) can be seen at -90dBrA, or 0.003%. No further signal harmonics can be seen above the -120dBrA noise floor. On the left side of the signal peak, the dominant peak is from the power supply’s second harmonic (120Hz) at -70dBrA, or 0.03%, while higher-order even-order harmonics can also be seen at -80dBrA, or 0.01%, and below.
FFT spectrum, 1kHz - MC input
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sinewave stimulus for the MC configuration, which results in the reference voltage of 1Vrms (0dBrA) at the output. Signal harmonics are dominated by the second harmonic (2kHz) at a high -60dBrA, or 0.1%, while the third harmonic (3kHz) can be seen at -90dBrA, or 0.003%. No further signal harmonics can be seen above the -120dBrA noise floor. On the left side of the signal peak, the dominant peak is from the power supply’s primary (60Hz) frequency at -60dBrA, or 0.1%, for the left channel, while the right channel is at -80dBrA, or 0.01%. Even-order power-supply related harmonics can also be seen at -70dBrA, or 0.03%, and below, all the way out to 5-6kHz.
FFT spectrum, 50Hz - MM input
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output for the MM 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. Signal harmonics are dominated by the second harmonic (100Hz) at a high -60dBrA, or 0.1%, while the third harmonic (150kHz) can be seen at -90dBrA, or 0.003%. No further signal harmonics can be seen above the -120dBrA noise floor. The dominant power-supply-related peak is at 120Hz at -70dBrA, or 0.03%.
FFT spectrum, 50Hz - MC input
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sinewave stimulus for the MC configuration, which results in the reference voltage of 1Vrms (0dBrA) at the output. Signal harmonics are dominated by the second harmonic (100Hz) at a high -60dBrA, or 0.1%, while the third harmonic (150Hz) can be seen at -90dBrA, or 0.003%. No further signal harmonics can be seen above the -110dBrA noise floor. Power-supply-related noise is dominated by the 60Hz peak at -60dBrA, or 0.1%, for the left channel, while the right channel is at -80dBrA, or 0.01%. The 120Hz power-supply-related harmonic can also be seen at -70dBrA, or 0.03%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MM input
Above is an FFT of the IMD products for an 18kHz and 19kHz summed sinewave stimulus tone for the MM configuration. The input rms values are set so that if summed (for a mean frequency of 18.5kHz), would yield 1Vrms (Reference or 0dBRa) at the output. Here we find the second-order modulation product (i.e., the difference signal of 1kHz) at a very high -30dBrA, or 3%. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) sitting at a -80dBrA, or 0.01%. This is a very poor IMD result for a phono preamplifier.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MC
The last graph is an FFT of the IMD products for an 18kHz and 19kHz summed sinewave stimulus tone for the MC configuration. The input rms values are set so that if summed (for a mean frequency of 18.5kHz), would yield 1Vrms (Reference or 0dBRa) at the output. Here we find the second-order modulation product (i.e., the difference signal of 1kHz) at a very high -30dBrA, or 3%. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) sitting at a -80dBrA, or 0.01%. Once again, this is a very poor IMD result for a phono preamplifier.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Jason Thorpe on SoundStage! Hi-Fi on July 1, 2023
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The Meitner Audio DS-EQ2 was conditioned for 30 minutes at 1Vrms at the output before any measurements were taken.
The DS-EQ2 phono preamp is designed to operate with DS Audio optical cartridges, and therefore operates differently from a conventional phono preamp designed for moving-magnet (MM) or moving-coil (MC) cartridges. As per DS Audio’s technical information page, these optical cartridges are an “amplitude proportional type” transducer, as opposed to a “velocity proportional type” transducer found in record cutting heads and both MM and MC cartridges, which operate on electromagnetic induction.
In terms of measuring the DS-EQ2 phono preamp with the APx555 analyzer, certain issues needed to be overcome. For a detailed description of these issues, along with test set-up configurations, as well as an explanation of how our DS Audio inverted EQ curve was derived, please see our measurements of the DS Audio DS 003 phono preamp.
The DS-EQ2 offers one pair of unbalanced RCA inputs, and one pair of unbalanced (RCA) outputs. There is a switch on the front panel that will enable a high-pass filter. Unless otherwise stated, all measurements were taken with the high-pass filter disabled. Using these settings, to achieve the reference output voltage of 1Vrms at 1kHz at the DS-EQ2 outputs, 125mVrms was required at the output of the APx555.
Primary measurements
Our primary measurements revealed the following (unless specified, assume a 1kHz sinewave, 1Vrms output into a 100k ohms load, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -106.8dB | -108.0dB |
DC offset | <0.4mV | <1.4mV |
Gain | 18.13dB | 18.15dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-93dB | <-93dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-93dB | <-93dB |
Maximum output voltage (at clipping 1% THD+N) | 9.5Vrms | 9.5Vrms |
Noise level (A-weighted) | <85uVrms | <85uVrms |
Noise level (unweighted) | <229uVrms | <241uVrms |
Output impedance | 151 ohms | 151 ohms |
Signal-to-noise ratio (A-weighted) | 81.3dB | 81.3dB |
Signal-to-noise ratio (unweighted) | 72.8dB | 72.5dB |
THD (unweighted) | <0.0019% | <0.0019% |
THD+N (A-weighted) | <0.0085% | <0.0085% |
THD+N (unweighted) | <0.023% | <0.024% |
Frequency response
In our measured frequency-response (relative to 1kHz) plots above measured at the left and right outputs, the blue/red traces are with the high-pass filter (HPF) disabled, while the purple and green are with the HPF enabled. The DS Audio inverted EQ is applied to the input sweep to emulate the output of the DS Audio optical cartridge. With the DS-EQ2, we find an exceptionally flat response from 20Hz to 20kHz, with only a small bass lift of about 0.5dB at 20Hz with the HPF disabled. With the HPF enabled, we are at -3dB at 20Hz. In the graph above and some of the graphs below, we see two visible traces; the left channel (blue or purple) and the right channel (red or green). On other graphs, only one trace may be visible, this is because the left and right channels are tracking extremely closely, so as not to show a difference with the chosen axis scales.
Frequency response (absolute gain with no EQ applied)
Above is the frequency response plot in terms of absolute gain with no EQ applied. In terms of the shape of the response curve, we find as expected, roughly the mirror image of our DS Audio inverted EQ curve. Absolute gain ranges from about 4dB at 20Hz, to 18dB at 1kHz, and about 24dB at 20kHz with the HPF disabled. With the HPF enabled, we are at 0dB at 20Hz.
Phase response
Above is the phase response of the DS-EQ2, from 20Hz to 20kHz. The right channel has inverted polarity; however, this is intentional, to match the behavior of the optical cartridge, which has its polarity inversed on one channel. Since the phono preamp must implement a combination of the RIAA equalization curve and a compensation curve for the inherent behavior of the optical cartridge, phase shift at the output is inevitable. Here we find the worst deviations in the left channel between -110 degrees at 20Hz, down to about -150 degrees at 200Hz and 5kHz.
THD ratio (unweighted) vs. frequency
The chart above shows THD ratios as a function of frequency, where the input sweep is EQ’d with our DS Audio inverted EQ curve. The unbalanced output voltage is maintained at the refrence 1Vrms. THD values are relatively flat, hovering between 0.001 and 0.002%, down to as low as 0.0006% at 20kHz.
THD ratio (unweighted) vs output voltage at 1kHz
The chart above shows THD ratios as a function of output voltages at 1kHz. THD values at 100mVrms are around 0.01%, then dip as low as 0.0006% between 2 and 3Vrms, then a rise to the “knee” just above 8Vrms, then up to the 1% THD value for both inputs at 9.5Vrms. It’s important to mention that anything above 1-2Vrms is not typically required for most line-level preamps or integrated amps.
THD+N ratio (unweighted) vs output voltage at 1kHz
Above we can see a plot of THD+N ratios as a function of output voltages at 1kHz. THD+N values at 100mVrms are at 0.2%, then dip as low as 0.003% at the “knee” at 8Vrms, then a steady rise up to the 1% mark at 9.5Vrms.
THD+N ratio (A-weighted) vs output voltage at 1kHz
Above we can see a plot of THD+N ratios as a function of output voltages at 1kHz. THD+N (A-weighted) values at 100mVrms are just below 0.1%, then dip as low as 0.002% at 5Vrms to the “knee” at 8Vrms, then a steady rise up to the 1% mark at 9.5Vrms.
FFT spectrum, 1kHz
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sinewave stimulus, which results in the reference voltage of 1Vrms (0dBrA). We find an exceptionally clean FFT, with only the second signal harmonic (2kHz) barely visible above the noise floor at -110dBrA, or 0.0003%. On the left side of the signal peak, the 60Hz power-supply fundamental is visible at a very low -110dBRa, or 0.0003%.
FFT spectrum, 50Hz
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the left and right outputs. 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 find an exceptionally clean FFT, with only the second signal harmonic barely visible above the noise floor at -115dBrA, or 0.0002%. On the left side of the signal peak, the 60Hz power-supply fundamental is visible at a very low -110dBRa, or 0.0003%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus)
The last graph is an FFT of the IMD products for an 18kHz and 19kHz summed sinewave stimulus tone at at the outputs. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 1Vrms (0dBrA) at the output. Once again we see a squeaky clean FFT, this time, with no visible peaks above the -120dBrA noise floor at the second-order (1kHz) or third-order (17 and 20kHz) IMD locations.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Philip Beaudette on SoundStage! Hi-Fi on June 1, 2023
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The S3 B was conditioned for 30 minutes at 2Vrms (1Vrms unbalanced) at the output before any measurements were taken.
The S3 B offers one pair of unbalanced (RCA) and balanced (5-pin mini XLR) inputs, for a moving-magnet (MM) or moving coil (MC) cartridge, selectable by a gain switch (40/45/60/65 dB, unbalanced output) on the front panel. There are both unbalanced (RCA) and balanced (XLR) outputs. Besides the extra 6dB in gain between the balanced and unbalanced outputs, we found no appreciable differences in terms of THD+N; however, 1kHz FFTs are still shown in this report for every input/output configuration for comparison. Also included are a grounding post, a subsonic filter, four capacitive loading settings (50/150/300/400pf), and five resistive loading settings (10, 50, 100, 1000, 47k ohms).
Unless otherwise specified, the balanced inputs and outputs were used for all measurements, with the subsonic filter off, capacitive loading at 50pF. For the MM configuration, gain was set to 40dB (46dB with balanced outputs) and 47k ohms loading, while the MC configuration was set to 60dB (66dB with balanced outputs) and 100-ohm loading. Using the default settings above, to achieve the reference output voltage of 2Vrms (1Vrms unbalanced) at 1kHz, 10mVrms was required with the MM configuration, and 1.4mVrms with the MC configuration. A custom female 5-pin mini XLR to dual female 3-pin XLR cable adapter was required to interface between the Audio Precision’s balanced outputs and the S3 B’s balanced inputs.
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Pro-Ject for the S3 B 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 set at its maximum (DC to 1MHz), assume, unless otherwise stated, 2Vrms balanced output into 200k ohms (100k ohms unbalanced) and a measurement input bandwidth of 10Hz to 90kHz, and the worst-case measured result between the left and right channels. For the gain setting measurements, the input impedance was set to 47k ohms.
Parameter | Manufacturer | SoundStage! Lab |
Input impedance | 10/50/100/1k/47k ohms | 10.2/56.2/99.4/981/52k ohms |
Gain | 40/45/60/65dB | 40.0/44.7/59.9/64.5dB |
Signal-to-noise ratio (MM/40dB, max output voltage) | 110dB (A-weighted) | 110dB (A-weighted) |
Signal-to-noise ratio (MC/60dB, max output voltage) | 90dB (A-weighted) | 90.8dB (A-weighted) |
THD at 1kHz (MM) | <0.001% | <0.0005% |
THD at 1kHz (MC) | <0.005% | <0.004% |
THD (MM, 20Hz-20kHz) | <0.008% | <0.004% |
THD (MC, 20Hz-20kHz) | <0.01% | <0.02% |
RIAA response accuracy | ±0.3dB (20Hz-20kHz) | +0.1/-0.38dB (20Hz-20kHz) |
Subsonic filter | -3dB at 20Hz (18dB/Oct) | -3dB at 20Hz (18dB/Oct) |
Our primary measurements revealed the following using the balanced MM configuration (unless specified, assume a 1kHz sinewave, 2Vrms output into a 200k ohms load, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -115.6dB | -114.4dB |
DC offset | <9.5mV | <9.5mV |
Gain (default) | 46.0dB | 46.1dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-82dB | <-82dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-97dB | <-97dB |
Input impedance | 51.7k ohms | 56.4k ohms |
Input impedance (unbalanced) | 51.6k ohms | 52.0k ohms |
Maximum output voltage (at clipping 1% THD+N) | 21.2Vrms | 21.2Vrms |
Noise level (A-weighted) | <55uVrms | <55uVrms |
Noise level (unweighted) | <120uVrms | <120uVrms |
Output impedance | 199.6 ohms | 200 ohms |
Output impedance (unbalanced) | 122.0 ohms | 122.4 ohms |
Overload margin (relative 5mVrms input, 1kHz) | 26.6dB | 26.6dB |
Overload margin (relative 5mVrms input, 20Hz) | 7.6dB | 7.53dB |
Overload margin (relative 5mVrms input, 20kHz) | 33.9dB | 33.9dB |
Signal-to-noise ratio (A-weighted) | 90.2dB | 90.2dB |
Signal-to-noise ratio (unweighted) | 84.5dB | 84.9dB |
THD (unweighted) | <0.0005% | <0.0005% |
THD+N (A-weighted) | <0.0027% | <0.0027% |
THD+N (unweighted) | <0.0057% | <0.0065% |
Our primary measurements revealed the following using the balanced MC configuration (unless specified, assume a 1kHz sinewave, 2Vrms output into a 200k ohms load, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -100.8dB | -100.1dB |
DC offset | <9.5mV | <9.5mV |
Gain (default) | 65.8dB | 65.9dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-81dB | <-81dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-78dB | <-78dB |
Input impedance | 100 ohms | 99.7 ohms |
Input impedance (unbalanced) | 99.6 ohms | 99.2 ohms |
Maximum output voltage (at clipping 1% THD+N) | 21.1Vrms | 21.1Vrms |
Noise level (A-weighted) | <530uVrms | <530uVrms |
Noise level (unweighted) | <1.1mVrms | <1.1mVrms |
Output impedance | 199.6 ohms | 200 ohms |
Output impedance (unbalanced) | 122.0 ohms | 122.4 ohms |
Overload margin (relative 0.5mVrms input, 1kHz) | 29.7dB | 29.7dB |
Overload margin (relative 0.5mVrms input, 20Hz) | 11.1dB | 11.1dB |
Overload margin (relative 0.5mVrms input, 20kHz) | 50.1dB | 50.1dB |
Signal-to-noise ratio (A-weighted) | 70.1dB | 70.4dB |
Signal-to-noise ratio (unweighted) | 64.7dB | 65.2dB |
THD (unweighted) | <0.0043% | <0.0043% |
THD+N (A-weighted) | <0.027% | <0.027% |
THD+N (unweighted) | <0.06% | <0.06% |
Frequency response - MM input
In our measured frequency-response plots above for the MM configuration measured at the balanced output, the blue/red traces are with the subsonic filter disengaged, while the purple and green represent the responses with the subsonic filter. An inverse RIAA EQ is applied to the input sweep, so that if a device were to track the RIAA curve perfectly, a flat line would emerge. The S3 B is within +/-0.1dB or so of flat from 20Hz to 10kHz. These data just about corroborate Proj-Ject’s claim of 20Hz to 20kHz +/-0.3dB—we measured -0.38dB at 20kHz. With the subsonic filter engaged, there is steep attenuation below 30Hz at 18dB/octave with the corner frequency at 20Hz, as advertised. In the graph above and some of the graphs below, we see two visible traces: the left channel (blue or purple) and the right channel (red or green). On other graphs, only one trace may be visible, this is because the left and right channels are tracking extremely closely, so they do not show a difference with the chosen axis’ scales.
Frequency response - MC input
In our measured frequency-response plot above for the MC configuration, the S3 B yields virtually the same results as with the MM configuration above.
Phase response - MM input
Above is the phase response of the S3 B for the MM configuration, from 20Hz to 20kHz. The S3 B does not invert polarity. Since phono preamplifiers must implement the RIAA equalization curve, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case -50 to -60 degrees around 200Hz and 3-5kHz.
Phase response - MC input
Above is the phase response of the S3 B for the MC configuration, from 20Hz to 20kHz. The results are virtually identical to the MM configuration above.
THD ratio (unweighted) vs. frequency - MM and MC inputs
The chart above shows THD ratios as a function of frequency, where the input sweep is EQ’d with an inverted RIAA curve. The balanced output voltage is maintained at the refrence 2Vrms. The red/blue (L/R) traces represent the MM configuration, and purple/green for MC. For the MM configuration, THD values are very low, ranging from 0.003% at 20Hz down to 0.0003% at 1kHz (left channel), then up to 0.003% at 20kHz. The MC configuration yielded higher THD ratios, ranging from 0.03% at 20Hz, down to around 0.002% at 1 to 4kHz, then back up to 0.01% at 20kHz.
THD ratio (unweighted) vs output voltage at 1kHz - MM and MC inputs
The chart above shows THD ratios as a function of output voltage for the balanced output. The red/blue (L/R) traces represent the MM configuration, and purple/green for MC. For the MM configuration, THD values at 100mVrms are at 0.005%, then dip as low as 0.0003% at 2Vrms, then a steady rise up to 0.02% at the “knee” right around 20Vrms. For the MC configuration, THD values at 100mVrms are at 0.05%, then steadily decrease down to 0.002% at 3 to 5Vrms, then a steady rise up to 0.02% at the “knee” right around 18Vrms The 1% THD values for the both configurations are reached at 21.1Vrms at the output. It’s important to mention that anything above 1-2Vrms is not typically required for most line-level preamps or integrated amps.
THD+N ratio (unweighted) vs output voltage at 1kHz - MM and MC inputs
Above we can see a plot of THD+N ratios as a function of output voltage for the balanced output. The red/blue (L/R) traces represent the MM configuration, and purple/green for MC. For the MM configuration, THD+N values at 100mVrms are at 0.1%, then dip as low as 0.002% around 5 to 7Vrms, then a steady rise up to 0.02% at the “knee” right around 20Vrms. For the MC configuration, THD+N values at 100mVrms are at 1%, then dip as low as 0.015% around 10Vrms until the “knee”at 18Vrms.
THD+N ratio (A-weighted) vs output voltage at 1kHz - MM and MC inputs
Above we can see a plot of THD+N (A-weighted) ratios as a function of output voltage for the balanced output. The red/blue (L/R) traces represent the MM configuration, and purple/green for MC. For the MM configuration, THD+N values at 100mVrms are at 0.05%, then dip as low as 0.0015% around 5Vrms. For the MC configuration, THD+N values at 100mVrms are at 0.5%, then dip as low as 0.01% around 7 to 10Vrms.
FFT spectrum, 1kHz - MM input (balanced in, balanced out)
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sinewave stimulus for the MM configuration, which results in the reference voltage of 2Vrms (0dBrA) at the balanced output using the balanced inputs. Here we see clean results. Signal harmonics are low and can be seen at the second (2kHz) and third (3kHz) positions at -115/110dBrA (left/right), or 0.0002/0.0003%, and -120dBrA, or 0.0001%, respectively. On the left side of the signal peak, there are no power-supply-related harmonics visible.
FFT spectrum, 1kHz - MM input (balanced in, unbalanced out)
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sinewave stimulus for the MM configuration, which results in the reference voltage of 2Vrms (0dBrA) at the unbalanced output using the balanced inputs and the 45dB gain setting. Here we see clean results, but with signal harmonics at the second (2kHz) and third (3kHz) positions slightly higher (5-10dB) than with the balanced outputs and 40dB gain setting above. On the left side of the signal peak, there are no power-supply-related harmonics visible.
FFT spectrum, 1kHz - MM input (unbalanced in, balanced out)
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sinewave stimulus for the MM configuration, which results in the reference voltage of 2Vrms (0dBrA) at the balanced output using the unbalanced inputs. Here we see clean results, with the signal harmonics at the second (2kHz) and third (3kHz) positions essentially the same as with the balanced input and output configuration above. However, unlike the balanced input and output configuration above, on the left side of the signal peak, there is a visible but small power-supply related peak at 60Hz at -100dBrA, or 0.001%.
FFT spectrum, 1kHz - MM input (unbalanced in, unbalanced out)
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sinewave stimulus for the MM configuration, which results in the reference voltage of 2Vrms (0dBrA) at the unbalanced output using the unbalanced inputs and the 45dB gain setting. Here we see clean results, but with signal harmonics at the second (2kHz) and third (3kHz) positions slightly higher (5-10dB) than with the balanced outputs and 40dB gain setting above. Like the unbalanced input and balanced output configuration above, on the left side of the signal peak, there is a visible but small power-supply-related peak at 60Hz at -100dBrA, or 0.001%.
FFT spectrum, 1kHz - MC input
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sinewave stimulus for the MC configuration, which results in the reference voltage of 2Vrms (0dBrA) at the balanced output using the balanced inputs. Here we see clean results. Signal harmonics are virtually non-existent above the noise floor, with only the second (2kHz) harmonic peak visible just barely visible from the right channel at -100dBrA, or 0.001%. On the left side of the signal peak, there are no power-supply related harmonics visible above the higher noise floor due to the extra gain.
FFT spectrum, 50Hz - MM input
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the balanced output for the MM 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. Only the second (100Hz) signal harmonic can be seen at around -110dBrA, or 0.0003%. There are no power-supply-related harmonics visible.
FFT spectrum, 50Hz - MC input
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the balanced output for the MC 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. Only the second (100Hz) signal harmonic is barely visible above the noise floor at just below -90dBrA, or 0.003%. There are no power-supply-related harmonics visible.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MM input
Above is an FFT of the IMD products for an 18kHz and 19kHz summed sinewave stimulus tone for the MM configuration measured at the balanced output. The input RMS values are set so that if summed (for a mean frequency of 18.5kHz), would yield 2Vrms (Reference or 0dBRa) at the output. Here we find the second order modulation product (i.e., the difference signal of 1kHz) at -100dBrA, or 0.001%. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) sitting just above the -100dBrA level.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MC
The last graph is an FFT of the IMD products for an 18kHz and 19kHz summed sinewave stimulus tone for the MC input. Here we find that the second-order modulation product (i.e., the difference signal of 1kHz) is not visible above the -100dBrA noise floor. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) are lower than with the MM configuration above, sitting at around -110dBRa, or 0.0003%.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Matt Bonaccio on SoundStage! Hi-Fi on March 15, 2023
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The Lehmanaudio Decade Jubilee was conditioned for 30 minutes at 1Vrms (unbalanced) at the output before any measurements were taken.
The Decade offers one pair of unbalanced (RCA) inputs, for or a moving-magnet (MM) or moving-coil (MC) cartridge, selectable by a switch on the front panel. There are unbalanced (RCA) outputs. There is a gain switch on the front panel, which can set to High or Low. In MM mode, the two specified gain settings are 36 and 46dB. In MC mode, the two specified gain settings are 56 and 66dB. Also included are a grounding post (rear panel), a low-pass rumble filter (front panel), three resistive loading settings (100/1k/47k ohms, selected with dip switches on bottom panel), and eight capacitance settings (47/147/267/367/1047/1147/1267/1367pF, selected with dip switches on bottom panel).
Unless otherwise specified, the rumble filter was off, the MM gain set to 46dB with a 47k ohm input impedance, the MC gain set to 66dB of gain with 100 ohm input impedance, and the capacitance set to 47pF. The Decade power supply is external, and connects to the main unit using an umbilical terminated with a 4-pin XLR connector. Lower noise was achieved with the power-supply approximately 3′ away from the main unit. Using the default settings above, to achieve the reference output voltage of 1Vrms at 1kHz, 5.5mVrms was required with the MM input, and 0.62mVrms with the MC input.
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Lehmannaudio for the Decade Jubilee compared directly against our own. The published specifications are sourced from Lehmannaudio’s website or from the manual, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was set at its maximum (DC to 1MHz), assume, unless otherwise stated, 1Vrms output into 100k ohms and a measurement input bandwidth of 10Hz to 90kHz, and the worst-case measured result between the left and right channels. For the MC gain setting measurements, the input impedance was set to 47k ohms.
Parameter | Manufacturer | SoundStage! Lab |
Sensitivity for 775mV out (MM, 1kHz) | 3.8mVrms | 4.3mVrms |
Sensitivity for 775mV out (MC, 1kHz) | 0.38mVrms | 0.39mVrms |
Maximum input level (MM, 1kHz) | 45mV | 45mV |
Maximum input level (MC, 1kHz) | 4.5mV | 4.5mV |
Signal-to-noise ratio (unweighted, MM, 775mV out) | 78dB | 78dB |
Signal-to-noise ratio (unweighted, MM, 775mV out) | 69dB | 69dB |
Gain (dB) | 36/46/56/66 | 35.5/45.1/56.1/65.7 |
Channel separation (10kHz) | >80dB | 113dB |
Input impedance | 47k/1k/100 ohms | 53k/1.2k/98 ohms |
Output impedance | 5 ohms | 9.8 ohms |
Channel mismatch | <0.5dB | 0.4dB |
Bass filter | 50Hz, 6dB/oct | 50Hz, 6dB/oct |
Our primary measurements revealed the following using the unbalanced MM input (unless specified, assume a 1kHz sinewave, 1Vrms output into a 100k ohms load, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -113.5dB | -113.6dB |
DC offset | <9mV | <2mV |
Gain (High) | 45.1dB | 45.5dB |
Gain (Low) | 35.5dB | 35.9dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-95dB | <-95dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-95dB | <-95dB |
Input impedance | 53k ohms | 52k ohms |
Maximum output voltage (at clipping 1% THD+N) | 8.7Vrms | 8.7Vrms |
Noise level (A-weighted) | <42uVrms | <42uVrms |
Noise level (unweighted) | <105uVrms | <110uVrms |
Output impedance | 9.8 ohms | 9.4 ohms |
Overload margin (relative 5mVrms input, 1kHz) | 19.8dB | 19.4dB |
Overload margin (relative 5mVrms input, 20Hz) | 1.3dB | 0.88dB |
Overload margin (relative 5mVrms input, 20kHz) | 31.9dB | 31.4dB |
Signal-to-noise ratio (A-weighted) | 86.9dB | 87.0dB |
Signal-to-noise ratio (unweighted) | 79.5dB | 79.2dB |
THD (unweighted) | <0.001% | <0.001% |
THD+N (A-weighted) | <0.0044% | <0.0042% |
THD+N (unweighted) | <0.01% | <0.01% |
Our primary measurements revealed the following using the unbalanced MC input (unless specified, assume a 1kHz sinewave, 1Vrms output into a 200k ohms load, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -101.8dB | -96.8dB |
DC offset | <10mV | <3mV |
Gain (High) | 64.2dB | 64.6dB |
Gain (Low) | 54.6dB | 54.9dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-85dB | <-85dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-85dB | <-85dB |
Input impedance | 98.6 ohms | 98.7 ohms |
Maximum output voltage (at clipping 1% THD+N) | 8.7Vrms | 8.7Vrms |
Noise level (A-weighted) | <135uVrms | <140uVrms |
Noise level (unweighted) | <350uVrms | <350uVrms |
Output impedance | 9.8 ohms | 9.4 ohms |
Overload margin (relative 0.5mVrms input, 1kHz) | 20.7dB | 20.3dB |
Overload margin (relative 0.5mVrms input, 20Hz) | 2.3dB | 2.0dB |
Overload margin (relative 0.5mVrms input, 20kHz) | 32.8dB | 32.5dB |
Signal-to-noise ratio (A-weighted) | 76.2dB | 76.3dB |
Signal-to-noise ratio (unweighted) | 70.2dB | 68.9dB |
THD (unweighted) | <0.002% | <0.002% |
THD+N (A-weighted) | <0.013% | <0.013% |
THD+N (unweighted) | <0.032% | <0.036% |
Frequency response - MM input
In our measured frequency-response plots above for the MM input, the blue/red traces are with the rumble-filter disengaged, while the purple and green represent the responses with the rumble filter. An inverse RIAA EQ is applied to the input sweep, so that if a device were to track the RIAA curve perfectly, a flat line would emerge. The Decade is within +/-0.1dB or so of flat from 300Hz to 50kHz, and about -0.8dB at 20Hz. As specified by Lehmann Audio, the rumble filter applies low-pass filtering at 6dB/octave (first order) with a 50Hz corner frequency (-3dB). This is an unusually high corner frequency for a rumble filter. In the graph above and some of the graphs below, we see two visible traces: the left channel (blue or purple) and the right channel (red or green), which means slight differences can be seen due to the scaling used. On other graphs, only one trace may be visible, which is because the left and right channels are tracking extremely closely and the chosen scaling does not reveal subtle differences.
Frequency response - MC input
In our measured frequency-response plot above for the MC input, the Decade Jubilee yields virtually the same results as with the MM input above.
Phase response - MM input
Above is the phase response of the Decade Jubilee for the MM input, from 20Hz to 20kHz. The blue/red traces are with the rumble filter disengaged, while the purple and green represent the responses with the rumble filter. Since phono preamplifiers must implement the RIAA equalization curve, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case -60 degrees around 200Hz and 5kHz, and +40 degrees at 20Hz with the rumble filter engaged. We can also see from this that the Decade Jubilee does not invert polarity.
Phase response - MC input
Above is the phase response of the Decade for the MC input, from 20Hz to 20kHz. The blue/red traces are with the rumble filter disengaged, while the purple and green represent the responses with the rumble filter. The Decade yields virtually the same results as with the MM input above.
THD ratio (unweighted) vs. frequency - MM and MC inputs
The chart above shows THD ratios as a function of frequency, where the input sweep is EQ’d with an inverted RIAA curve. The output voltage is maintained at the refrence 1Vrms. The red/blue (left/right) traces represent the MM input, and purple/green for the MC input. For the MM input, THD values are very low, ranging from 0.003% at 20Hz down to 0.0007% at 2kHz, then up to 0.002% at 20kHz. The MC input yielded higher THD ratios, ranging from 0.03% at 20Hz, down to around 0.001% at 5kHz, then back up to 0.002% at 20kHz.
THD ratio (unweighted) vs output voltage at 1kHz - MM and MC inputs
The chart above shows THD ratios as a function of output voltage. The red/blue (left/right) traces represent the MM input, and purple/green for MC. For the MM input, THD values at 100mVrms are at 0.005%, then dip as low as 0.0007% just below 1Vrms, then there is a steady rise to nearly 0.05% at the “knee” at roughly 8Vrms. For the MC input, THD values at 100mVrms are at 0.01%, then steadily decrease down to just below 0.002% between 1 and 2Vrms, then align with the MM THD ratios beyond 2Vrms. The 1% THD values for both inputs are reached at 8.7Vrms at the output. It’s important to mention that anything above 1-2Vrms is not typically required for most line-level preamps or integrated amps.
THD+N ratio (unweighted) vs output voltage at 1kHz - MM and MC inputs
Above we can see a plot of THD+N ratios as a function of output voltage. The red/blue (left/right) traces represent the MM input, and purple/green for MC. For the MM input, THD+N values at 100mVrms are at 0.1%, then dip as low as 0.005% around 3Vrms. For the MC input, THD+N values at 100mVrms are at 0.3%, then dip as low as 0.01% between 3 and 5Vrms.
THD+N ratio (A-weighted) vs output voltage at 1kHz - MM and MC inputs
Above we can see a plot of THD+N (A-weighted) ratios as a function of output voltage. The red/blue (left/right) traces represent the MM input, and purple/green for MC. For the MM input, THD+N values at 100mVrms are at 0.05%, then dip as low as 0.003% around 2Vrms. For the MC input, THD+N values at 100mVrms are at 0.15%, then dip as low as 0.005% between at 3Vrms.
FFT spectrum, 1kHz - MM input
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sinewave stimulus for the MM input, which results in the reference voltage of 1Vrms (0dBrA) at the output. Here we see a clean result. Signal harmonics are low, with the second (2kHz) at -105dBrA, or 0.0006%, and the third harmonic (3kHz) at -110dBrA, or 0.0003%. On the left side of the signal peak, there is a very small 60Hz power-supply fundamental peak at -100dBrA, or 0.001%, and it’s second harmonic (120Hz) at -105dBrA, or 0.0006%.
FFT spectrum, 1kHz - MC input
Shown above is an FFT of a 1kHz input sinewave stimulus for the MC input. As there is 20dB more gain with the MC setting, predictably the noise floor is elevated compared to the MM input FFT, although, only by about 10dB. We can just barely see the second signal harmonic (2kHz) at just below -100dBrA, or 0.001%. The 60Hz power-supply noise peak is more pronounced due to the higher gain, at -80dBrA, or 0.01%. The second (120Hz) through seventh (420Hz) noise harmonics can also be seen at -80dBrA, or 0.01%, and below.
FFT spectrum, 50Hz - MM input
Shown above is the FFT for a 50Hz input sinewave stimulus for the MM 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 second (100Hz) and third (150Hz) signal harmonics can be seen at -100dBrA, or 0.001%, and -110dBrA, or 0.0003%, respectively. The 60Hz primary power-supply related noise peak can be seen at -105dBrA, or 0.0006%, while the second (120Hz) harmonic is at -105/-115dBrA (left/right), or 0.0006/0.0002%.
FFT spectrum, 50Hz - MC input
Shown above is the FFT for a 50Hz input sinewave stimulus for the MC 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 second (100Hz) signal harmonic can be seen at -95dBrA, or 0.002%. The power-supply noise-related peaks dominate the FFT, with the 60Hz primary at -75/-80dBrA (left/right), or 0.02/0.01%. The second (120Hz) through eighth (480Hz) noise harmonics can also be seen at -80dBrA, or 0.01%, down to -105dBrA, or 0.0006%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MM input
Above is an FFT of the IMD products for an 18kHz and 19kHz summed sinewave stimulus tone for the MM input. The input rms values are set so that if summed (for a mean frequency of 18.5kHz), would yield 1Vrms (Reference or 0dBRa) at the output. Here we find the second- order modulation product (i.e., the difference signal of 1kHz) at -100dBrA, or 0.001%. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) sitting at a vanishingly low -120dBrA, or 0.0001%. This is a clean IMD result for a phono preamplifier.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MC
The last graph is an FFT of the IMD products for an 18kHz and 19kHz summed sinewave stimulus tone for the MC input. Here we find the second-order modulation product (i.e., the difference signal of 1kHz) is at -95dBrA, or 0.002%. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) at roughly the same amplitude as the MM setting, sitting at or just above -120dBRa, or 0.0001%.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Jason Thorpe on SoundStage! Hi-Fi on October 1, 2022
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The EMM Labs DS-EQ1 was conditioned for 30 minutes at 2Vrms at the balanced output (1Vrms unbalanced) before any measurements were taken.
The DS-EQ1 phono preamp is designed to operate with DS Audio optical cartridges, and therefore operates differently from a conventional phono preamp designed for moving-magnet (MM) or moving-coil (MC) cartridges. As per DS Audio’s technical information page, these optical cartridges are an “amplitude proportional type” transducer as opposed to a “velocity proportional type” transducer found in record-cutting heads and both MM and MC cartridges, which operate on electromagnetic induction.
In terms of measuring the DS-EQ1 phono preamp with the APx555 analyzer, certain issues needed to be overcome. For a detailed description of these issues, along with test set-up configurations, as well as an explanation of how our DS Audio inverted EQ curve was derived, please see our measurements of the DS Audio DS-003 phono preamp.
The EMM Labs DS-EQ1 offers one pair of unbalanced (RCA) inputs and one pair of unbalanced (RCA) and balanced (XLR) outputs. There is a switch on the front panel that will enable a high-pass filter. Unless otherwise stated, all measurements were taken with the high-pass filter disabled and using the balanced outputs. Aside from the extra 6dB of gain measured at the balanced outputs, no appreciable differences were seen in terms of noise and THD when comparing both outputs. To achieve the reference output voltage of 2Vrms at 1kHz at the DS-EQ1 outputs, 85mVrms was required at the output of the APx555.
The DS-EQ1 uses a switching power supply, which results in a peak at roughly 70kHz (see FFTs below). Our typical bandwidth filter setting of 10Hz-90kHz was maintained for THD measurements; however, for noise and THD+N measurements, a 10Hz-45kHz bandwidth was used, to ignore the 70kHz peak.
Primary measurements
Our primary measurements revealed the following (unless specified, assume a 1kHz sine wave, 2Vrms output into a 200k ohms load, 10Hz to 45kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -105.2dB | -107.8dB |
DC offset | <1mV | <1mV |
Gain | 27.4dB | 27.4dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-96dB | <-96dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-93dB | <-93dB |
Maximum output voltage (at clipping 1% THD+N) | 22Vrms | 22Vrms |
Noise level (A-weighted) | <118uVrms | <118uVrms |
Noise level (unweighted) | <212uVrms | <212uVrms |
Output impedance (XLR) | 299 ohms | 299 ohms |
Output impedance (RCA) | 151 ohms | 151 ohms |
Signal-to-noise ratio (A-weighted) | 83.9dB | 83.8dB |
Signal-to-noise ratio (unweighted) | 79.4dB | 79.4dB |
THD (unweighted) | <0.001% | <0.001% |
THD+N (A-weighted) | <0.006% | <0.006% |
THD+N (unweighted) | <0.011% | <0.011% |
Frequency response
In our measured frequency-response plots above, the blue/red traces are with the high-pass filter (HPF) disabled, while the purple and green are with the HPF enabled. The DS Audio inverted EQ is applied to the input sweep to emulate the output of the DS Audio optical cartridge. We find an exceptionally flat response from 20Hz to 20kHz, with only a small bass lift of about 0.7dB at 20Hz with the HPF disabled. With the HPF enabled, it is at -3dB at 20Hz. In the graph above and some of the graphs below, we see two visible traces: the left channel (blue or purple) and the right channel (red or green). On other graphs, only one trace may be visible, this is because the left and right channels are tracking extremely closely, so as not to show a difference with the chosen axis scales.
Frequency response (absolute gain with no EQ applied)
Above is the frequency response plot in terms of absolute gain with no EQ applied, measured at the unbalanced outputs. The blue/red traces are with the high-pass filter (HPF) disabled, while the purple and green are with the HPF enabled. In terms of the shape of the response curve, we find, as expected, roughly the mirror image of our DS Audio inverted EQ curve when observing the gain response when the HPF is disabled. Absolute gain ranges from about 7.5dB at 20Hz to 21.5dB at 1kHz, and nearly 28dB at 20kHz with the HPF disabled. With the HPF enabled, it is at 3dB at 20Hz.
Phase response
Above is the phase response of the DS-EQ1, from 20Hz to 20kHz. The right channel has inverted polarity; however, this is intentional, to match the behavior of the optical cartridge. Since the phono preamp must implement a combination of the RIAA equalization curve and a compensation curve for the inherent behavior of the optical cartridge, phase shift at the output is inevitable. Here we find worst-case deviations in the left channel between -140 degrees at 200Hz, down to about -160 degrees at 200Hz and 7-8kHz.
THD ratio (unweighted) vs. frequency
The chart above shows THD ratios as a function of frequency, where the input sweep is EQ’d with our DS Audio inverted EQ curve. The balanced output voltage is maintained at the refrence 2Vrms. THD values are relatively flat, ranging from just over 0.001% at 20Hz, down to as low as 0.0003% at 20kHz.
THD ratio (unweighted) vs output voltage at 1kHz
The chart above shows THD ratios as a function of voltage at 1kHz. THD values at 100mVrms are around 0.02%, then dip as low as 0.0005% between 3 and 5Vrms, then a rise to the “knee” just below 20Vrms, then up to the 1% THD value for both inputs at 22Vrms. It’s important to mention that anything above 1-2Vrms is not typically required for most line-level preamps or integrated amps.
THD+N ratio (unweighted) vs output voltage at 1kHz
Above we can see a plot of THD+N ratios as a function of output voltages at 1kHz. THD+N values at 100mVrms are at 0.2%, then dip as low as 0.003% at 10Vrms, then a rise up to the “knee” just below 20Vrms.
THD+N ratio (A-weighted) vs output voltage at 1kHz
Above we can see a plot of THD+N ratios as a function of output voltage at 1kHz. THD+N (A-weighted) values at 100mVrms are at roughly 0.1%, then dip as low as 0.002% at 7-8Vrms then up to the “knee” just below 20Vrms.
FFT spectrum, 1kHz
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sine-wave stimulus, which results in the reference voltage of 2Vrms (0dBrA) at the balanced outputs. We find an exceptionally clean FFT, with only the second signal harmonic (2kHz) barely visible above the noise floor at -115dBrA, or 0.0002%. On the left side of the signal peak, the 60Hz power-supply fundamental is just barely visible at a very low -115dBRa, or 0.0002%.
FFT spectrum, 50Hz
Shown above is the FFT for a 50Hz input sine-wave stimulus. 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 find an exceptionally clean FFT, with the second signal harmonic at -110dBrA, or 0.0003%, and the third signal harmonic (150Hz) just barely visible above the noise floor at -120dBrA, or 0.0001%. On the left side of the signal peak, the 60Hz power-supply fundamental is visible at a very low -115dBRa, or 0.0002%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus)
The last graph is an FFT of the intermodulation distortion (IMD) products for an 18kHz and 19kHz summed sine-wave stimulus tone at the balanced outputs. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 2Vrms (0dBrA) at the output. Once again we see a squeaky-clean FFT, this time, with no visible peaks above the -120dBrA noise floor at the second-order (1kHz) or third-order (17 and 20kHz) IMD locations.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Jason Thorpe on SoundStage! Hi-Fi on July 15, 2022
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The DS Audio DS 003 was conditioned for 30 minutes at 1Vrms at the output before any measurements were taken.
The DS Audio DS 003 phono preamp is designed to operate with DS Audio optical cartridges, and therefore operates differently from a conventional phono preamp designed for moving magnet (MM) or moving coil (MC) cartridges. As per DS Audio’s technical information page, these optical cartridges are an “amplitude proportional type” transducer, as opposed to a “velocity proportional type” transducer found in record-cutting heads and both MM and MC cartridges, which operate on electromagnetic induction.
In terms of measuring the DS Audio DS 003 phono preamp with the APx555 analyzer, certain issues needed to be overcome. To accomplish this, we entered into a dialog with an engineer at DS Audio to ensure that the measurements were performed correctly.
The first issue was that the DS Audio preamp’s RCA input signal leads (left and right) have a -12VDC (no-load) bias to provide power to the LEDs inside the optical cartridge. The second issue was that the ground lead on the right RCA input is biased at +5VDC to provide power for other sections of the optical cartridge. The third issue was that of emulating the output of the optical cartridge in terms of both frequency response and output impedance, using the APx555 signal generator.
To solve the first issue, 2k ohms resistors were wired in series between the DS Audio’s RCA inputs and the APx555’s outputs, thereby limiting the current that the APx555 outputs would need to sink from the DS Audio’s DC voltage sources. The second issue was resolved by lifting the DS Audio right input ground connection (i.e., it was connected to nothing). In order to ensure that both left and right input signals to the DS Audio were referenced to ground, a connection was made between the DS Audio ground post and the APx555 left- and right-input ground posts (note: this wiring configuration is often utilized for conventional phono preamps to reduce noise). In order to ensure that the shield of the RCA cable between the APx555’s output 2 and the right input on the DS Audio were grounded on both ends, a short jumper was wired between the cable’s ground connection and the DS Audio ground post. The third issue was partially resolved at the same time as the first, as the characteristic output impedance of the optical cartridge, which operates as a current source, is 2k ohms. This left the inherent frequency response of the cartridge, and in turn, finding the correct inverted EQ curve to program into the APx555 signal generator for frequency sweeps.
The first component of the EQ curve is the same as for any other phono preamp: an inverted RIAA curve, as these optical cartridges are tracking the grooves from the same records as would an MM or MC cartridge. Records are encoded with an inverted RIAA EQ curve, and phono preamps must implement the RIAA EQ curve to restore a flat frequency response. The inverted RIAA curve is supplied by Audio Precision (AP). The second component of the EQ curve is the inherent response of the optical cartridge. As per our communications with DS Audio, the optical cartridge’s output follows that of a first-order low-pass filter with a 1Hz corner frequency. That is to say that it would be -3dB at 1Hz, -20dB at 10Hz, -26dB at 20Hz, -40dB at 100Hz, -46dB at 200Hz, -60dB at 1kHz, -66dB at 2kHz, -80dB at 10kHz, -86dB at 20kHz, and -100dB at 100kHz. To construct the DS Audio inverted EQ curve, we added the dB values at each frequency point in the supplied AP inverted RIAA EQ curve (44 points in total from 5Hz to 90kHz) to the dB values for a first-order low-pass filter with a 1Hz corner frequency (gain of 0dB) for the same frequency points. We then normalized the curve to 0dB at 1kHz, which required adding 60dB to each data point. The resulting EQ curve is as follows:
A comparison between the DS Audio phono preamp inverted EQ curve and the conventional inverted RIAA EQ curve used to evaluate conventional phono preamps can be seen below:
The DS Audio DS 003 offers one pair of unbalanced RCA inputs and two pairs of unbalanced (RCA) outputs, the latter labelled Output 1 and 2. Output 1 does not have a high-pass filter applied, but Output 2 does. There is also a switch labelled Cut Off for the high-pass filter that can be toggled between 30Hz and 50Hz. Unless otherwise stated, all measurements were taken using Output 1 and the Cut Off switch set to 30Hz. Using these settings, to achieve the reference output voltage of 1Vrms at 1kHz at the DS Audio DS 003 outputs, 92mVrms was required at the output of the APx555.
Primary measurements
Our primary measurements revealed the following (unless specified, assume a 1kHz sine wave, 1Vrms output into a 100k ohms load, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -80.9dB | -80.5dB |
DC offset | <-5mV | <4mV |
Gain | 20.8dB | 20.6dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-74dB | <-82dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-75dB | <-85dB |
Maximum output voltage (at clipping 1% THD+N) | 9.8Vrms | 9.8Vrms |
Noise level (A-weighted) | <42uVrms | <45uVrms |
Noise level (unweighted) | <98uVrms | <110uVrms |
Output impedance | 102 ohms | 121 ohms |
Signal-to-noise ratio (A-weighted) | 86.9dB | 86.1dB |
Signal-to-noise ratio (unweighted) | 80.2dB | 79.3dB |
THD (unweighted) | <0.016% | <0.005% |
THD+N (A-weighted) | <0.019% | <0.0071% |
THD+N (unweighted) | <0.019% | <0.012% |
Frequency response - Output 1
In our measured frequency-response plots above measured at Output 1, the blue/red traces are with the Cut Off switch to 30Hz, while the purple and green are with the switch set to 50Hz. The DS Audio inverted EQ curve is applied to the input sweep to emulate the output of the DS Audio optical cartridge. From 100Hz to 80kHz, we find a very flat response, with deviations in the +/- 0.5dB range. Below 100Hz, there is a distinct lift in the bass region. With the Cut Off switch at the 30Hz position, there’s 4.5dB of boost at 20Hz (relative to 1kHz), and with the Cut Off switch at the 50Hz position, just under 2.5dB of boost at 20Hz. We would normally refer to this as a deviation; however, in our discussions with DS Audio, they have said that this is intentional, with the following rationale: “as most cutter-heads, except for Neumann's SX74, have a small roll-off in low frequencies below 40Hz, DS Audio implements a small boost in this frequency range.” It is odd, however, that the Cut Off switch has any effect at all on Output 1, since Output 2 has the high-pass filter applied, but Output 1 does not. In the graph above and some of the graphs below, we see two visible traces: the left channel (blue or purple) and the right channel (red or green). On other graphs, only one trace may be visible, which is because the left and right channels are tracking extremely closely, so as not to show a difference with the chosen axis scales.
Frequency response - Output 1 (absolute gain with no EQ applied)
Above is the frequency response plot in terms of absolute gain with no EQ applied for Output 1. In terms of the shape of the response curve, we find, as expected, roughly the mirror image of our DS Audio inverted EQ curve. Absolute gain ranges from about 10.5dB at 20Hz, to 21dB at 1kHz, and about 26.5dB at 20kHz with the Cut Off switch at the 30Hz position. In the 50Hz position, we are at 8dB at 20Hz.
Frequency response - Output 2
In our measured frequency-response plots above measured at Output 2, the blue/red traces are with the Cut Off switch set to 30Hz, while the purple and green are with the switch set to 50Hz. The DS inverted EQ curve is applied to the input sweep to emulate the output of the DS Audio optical cartridge. From 100Hz to 80kHz, we find a very flat response, with deviations in the +/- 0.5dB range. Below 100Hz, there is a small lift in the bass response region, followed by a steep cutoff. With the Cut Off switch at the 30Hz position, we are down 2dB at 20Hz, and with the Cut Off switch at the 50Hz position, we are down 4.5dB at 20Hz. Both slopes below 20Hz are approximately 18dB/octave. Output 2 offers the same equalization and gain as Output 1, but with the addition of a high-pass filter to attenuate the lowest frequencies. Given that Output 1 yields intentional bass boost, for those looking for a flatter response, Output 2 should be used—although at the expense of additional phase shift.
Frequency response - Output 2 (absolute gain with no EQ applied)
Above is the frequency response plot in terms of absolute gain with no EQ applied for Output 2. Absolute gain ranges from about 2.5dB at 20Hz, 21dB at 1kHz, and about 26.5dB at 20kHz with the Cut Off switch at the 30Hz position. In the 50Hz position, we are at 0dB at 20Hz.
Phase response - Output 1
Above is the phase response of the DS 003, from 20Hz to 20kHz. The right channel has inverted polarity; however, this is intentional, to match the behavior of the optical cartridge. Since the phono preamp must implement a combination of the RIAA equalization curve and a compensation curve for the inherent behavior of the optical cartridge, phase shift at the output is inevitable. Here we find a worst case of about +60 degrees at 20Hz, dipping to +20 degrees at around 100Hz and 5kHz.
THD ratio (unweighted) vs. frequency
The chart above shows THD ratios as a function of frequency, where the input sweep is EQ’d with our DS Audio inverted EQ curve. The unbalanced output voltage is maintained at the refrence 1Vrms. THD values are relatively flat, with the right channel outperforming the left by almost 10dB, hovering from 0.01% at 20Hz, down to 0.005% from 100Hz to 10kHz, then up to 0.007% at 20kHz.
THD ratio (unweighted) vs output voltage at 1kHz
The chart above shows THD ratios as a function of Output 1 voltages at 1kHz. Between 300mVrms and about 2Vrms, the right channel outperforms the left channel, again by as much as 10dB. Right-channel THD values at 100mVrms are just under 0.005%, then dip as low as 0.002% around 0.5Vrms, then a slow rise to the 1% THD value for both inputs at 9.8Vrms. It’s important to mention that anything above 1-2Vrms is not typically required for most line-level preamps or integrated amps.
THD+N ratio (unweighted) vs output voltage at 1kHz
Above we can see a plot of THD+N ratios as a function of Output 1 voltages at 1kHz. THD+N values at 100mVrms are at 0.1% (left/right channels), then dip as low as 0.01% for the right channel at around 1Vrms, then a steady rise up to the 1% mark at 9.8Vrms.
THD+N ratio (A-weighted) vs output voltage at 1kHz
Above we can see a plot of THD+N (A-weighted) ratios as a function of Output 1 voltages at 1kHz. THD+N (A-weighted) values at 100mVrms are just below 0.05%, then dip as low as 0.006% at around 0.5Vrms (right) at 1Vrms, then a steady rise up to the 1% mark at 9.8Vrms.
FFT spectrum, 1kHz
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sine-wave stimulus, which results in the reference voltage of 1Vrms (0dBrA) at Output 1. There are two obvious signal harmonics at 2kHz and 3kHz, at -75/-90dBrA (left/right), or 0.02/0.003%, and -90dBrA, respectively. On the left side of the signal peak, the 60Hz power-supply fundamental peak is at -110/-90dBrA (left/right), or 0.0003/0.003%. Subsequent even-ordered (i.e., 120Hz, 240Hz, 360Hz) power-supply-related harmonics are seen at -95dBRa, or 0.002%, and below.
FFT spectrum, 50Hz
Shown above is the FFT for a 50Hz input sine-wave stimulus measured at Output 1. 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 second and third harmonics from the 50Hz signal (100 and 150Hz) are evident at -80/-90dBrA (left/right), or 0.01/0.003%, and -85dBrA, or 0.006%, respectively. Power-supply-related noise peaks can be seen throughout at levels of -90dBrA, or 0.003%, and below.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus)
The last graph is an FFT of the intermodulation distortion (IMD) products for an 18kHz and 19kHz summed sinewave stimulus tone at Output 1. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 1Vrms (0dBrA) at the output. Here we find the second-order modulation product (i.e., the difference signal of 1kHz) is at -80/95dBrA (left/right), or 0.01/0.002%. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) at just above -95dBRa, or 0.002%.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Philip Beaudette on SoundStage! Hi-Fi on April 15, 2022
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The Simaudio Moon 310LP was conditioned for 30 minutes at 1Vrms (2Vrms balanced) at the output before any measurements were taken.
The 310LP offers one pair of unbalanced RCA inputs that can be configured for or a moving-magnet (MM) or moving-coil (MC) cartridge. There are both unbalanced (RCA) and balanced (XLR) outputs. Besides the extra 6dB in gain between the balanced and unbalanced outputs, we found no appreciable differences in terms of THD+N.
There are five gain settings, selectable by moving jumpers on the circuit board: 40, 54, 60, 66dB. Of note, Simaudio specifies all of their gain values for the unbalanced outputs; add 6dB for each gain value if using the balanced outputs. There are five resistive-loading settings: 10, 100, 470, 1000, 47k ohms. There are also capacitive-loading settings: 0, 100, 470 pF. In addition, either RIAA or IEC EQ curves can be selected.
Unless otherwise specified, the unbalanced outputs were used for all measurements, with the RIAA EQ curve, with the following MM settings: 40dB, 47k ohms, 0pF. The MC settings were: 60dB, 100 ohms, 0pF. Using the default settings above, to achieve the reference output voltage of 1Vrms (2Vrms balanced) at 1 kHz, 10mVrms was required with the MM configuration, while 1.2mVrms was needed with the MC configuration.
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Simaudio for the 310LP compared directly against our own measurements. The published specifications are sourced from Simaudio’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, 1Vrms unbalanced output into 100k ohms and a measurement input bandwidth of 10Hz to 90kHz, and the worst-case measured result between the left and right channels. For the gain setting measurements, the input impedance was set to 47k ohms.
Parameter | Manufacturer | SoundStage! Lab |
Gain settings | 40/54/60/66dB | 40.1/54.7/ 59.8/65.4dB |
Input overload (1kHz at 40/54/60/66dB) | 58/11/6/3mVrms | 98/18.4/10.2/5.4mVrms |
Signal-to-noise ratio (1kHz, 9Vout at 40dB, A-weighted) | 110dB | 117.1dB |
Signal-to-noise ratio (1kHz, 9Vout at 66dB, A-weighted) | 88dB | 94.5dB |
RIAA response accuracy | 20Hz to 20kHz +/-0.5dB | 20Hz to 20kHz +/-0.25dB |
IEC curve effect | -7dB at 10Hz | -7dB at 10Hz |
Resistive loading | 10/100/470/1000/47k ohms | 9.9/98/464/967/51k |
Crosstalk at 1kHz | -100dB | -102.3dB |
Intermodulation distortion (19+20kHz, 1:1, 40dB gain, 10mVin) | 0.009% | 0.005% |
THD (20Hz to 6kHz)* | 0.001% | 0.002-0.0001% |
Output impedance | 50 ohms | 51 ohms |
* Simaudio’s published specification is actually THD (20Hz-20kHz); however, after speaking with someone at the company, it was discovered that this measurement is also bandwidth limited to 20kHz, thereby limiting the highest frequency (where second and third harmonics can be captured) to 6kHz.
Our primary measurements revealed the following using the unbalanced input with the MM configuration (unless specified, assume a 1kHz sine wave, 1Vrms output into a 100k ohms load, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -112.0dB | -105.9dB |
DC offset | <0.7mV | <0.6mV |
Gain (default) | 40.1dB | 40.2dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-81dB | <-85dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-98dB | <-101dB |
Input impedance | 51k ohms | 54k ohms |
Maximum output voltage (at clipping 1% THD+N) | 9.8Vrms | 9.8Vrms |
Noise level (A-weighted) | <11uVrms | <11uVrms |
Noise level (unweighted) | <40uVrms | <40uVrms |
Output impedance | 51 ohms | 51 ohms |
Output impedance (balanced) | 100 ohms | 101 ohms |
Overload margin (relative 5mVrms input, 1kHz) | 25.8dB | 25.8dB |
Overload margin (relative 5mVrms input, 20Hz) | 6.7dB | 6.7dB |
Overload margin (relative 5mVrms input, 20kHz) | 34dB | 34dB |
Signal-to-noise ratio (A-weighted) | 98.0dB | 98.4dB |
Signal-to-noise ratio (unweighted) | 88.5dB | 87.1dB |
THD (unweighted) | <0.0002% | <0.0002% |
THD+N (A-weighted) | <0.001% | <0.001% |
THD+N (unweighted) | <0.005% | <0.005% |
Our primary measurements revealed the following using the unbalanced input with the MC configuration (unless specified, assume a 1kHz sine wave, 1Vrms output into a 100k ohms load, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -98.5dB | -90.9dB |
DC offset | <1.1mV | <0.7mV |
Gain (default) | 58.2dB | 58.3dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-59dB | <-63dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-79dB | <-81dB |
Input impedance | 98 ohms | 99 ohms |
Maximum output voltage (at clipping 1% THD+N) | 9.8Vrms | 9.8Vrms |
Noise level (A-weighted) | <75uVrms | <75uVrms |
Noise level (unweighted) | <250uVrms | <250uVrms |
Output impedance | 51 ohms | 51 ohms |
Output impedance (balanced) | 100 ohms | 101 ohms |
Overload margin (relative 0.5mVrms input, 1kHz) | 27.7dB | 27.7dB |
Overload margin (relative 0.5mVrms input, 20Hz) | 8.9dB | 8.9dB |
Overload margin (relative 0.5mVrms input, 20kHz) | 32.5dB | 32.5dB |
Signal-to-noise ratio (A-weighted) | 80.5dB | 81.2dB |
Signal-to-noise ratio (unweighted) | 73.2dB | 72.9dB |
THD (unweighted) | <0.0015% | <0.0015% |
THD+N (A-weighted) | <0.008% | <0.008% |
THD+N (unweighted) | <0.025% | <0.025% |
Frequency response - MM input
In our measured frequency-response plots above for the MM configuration measured at the unbalanced output, the blue and red traces (left and right channels) are with the RIAA EQ curve, while the purple and green (left and right channels) represent the responses with the IEC curve. An inverse RIAA EQ is applied to the input sweep, so that if a device were to track the RIAA curve perfectly, a flat line would emerge. The 310LP is within +/-0.25dB or so of flat from 20Hz to 20kHz, and about -0.25dB at 20Hz, and +0.1dB (right channel) at 20kHz. These data corroborate Simaudio’s claim of 20Hz to 20kHz +/-0.5dB. With the IEC curve engaged, there is a steep attenuation below 20Hz, with a -3dB point at 20Hz, and -7dB at 10Hz, as advertised. The worst-case channel-to-channel deviation is between 5kHz and 20kHz, where the right channel is less than 0.2dB hotter than the left. In the graph above and some of the graphs below, we see two visible traces; the left channel (blue or purple) and the right channel (red or green). On other graphs, only one trace may be visible. This is because the left and right channels are tracking extremely closely, so as not to show a difference with the chosen axis scales.
Frequency response - MC input
In our measured frequency-response plot above for the MC configuration, the 301LP yields virtually the same results as with the MM configuration above. The IEC curve (not shown), was also essentially the same.
Phase response - MM input
Above is the phase response of the 310LP for the MM configuration, from 20Hz to 20kHz. The 310LP does not invert polarity. Since phono preamplifiers must implement the RIAA equalization curve, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst-case -60 degrees around 200Hz and 5kHz.
Phase response - MC input
Above is the phase response of the 310LP for the MC configuration, from 20Hz to 20kHz. The 310LP does not invert polarity. As with the MM phase response, here we find a worst case of -60 degrees around 200Hz and 5kHz.
THD ratio (unweighted) vs. frequency - MM and MC inputs
The chart above shows THD ratios as a function of frequency, where the input sweep is EQ’d with an inverted RIAA curve. The unbalanced output voltage is maintained at the refrence 1Vrms. The red/blue traces (left and right channels) represent the MM configuration, and purple/green (left and right channels) for the MC configuration. For the MM configuration, THD values are very low, ranging from 0.002% at 20Hz down to 0.0001% around 1kHz, then rise to 0.003% at around 18kHz, then show a steep rise to 0.5% at 20kHz. The MC configuration yielded higher THD ratios, but are still admirably low, ranging from 0.015% at 20Hz, down to around 0.0007% around 1kHz, then back up to 0.015% at 20kHz. It’s important to explain the odd behavior for the MM configuration at high frequencies. The reason for this behavior is input overload at very high frequencies, causing distortion. Because of the RIAA EQ curve, it’s necessary to input roughly 100mVrms of signal amplitude at 20kHz to achieve a 1Vrms output. In the real world, with a real recording on an LP, a MM cartridge would never output anywhere near this voltage at 20kHz. So below . . .
. . . is the same chart, but with a targeted 0.5Vrms output instread of 1Vrms, to show the 310LP’s behavior without the input overload at high frequencies. Here we see for the MM configuration, THD ratios ranging from 0.003% at 20Hz down to 0.00015% around 2kHz, then a rise to 0.003% at around 20kHz.
THD ratio (unweighted) vs output voltage at 1kHz - MM and MC inputs
The chart above shows THD ratios as a function of output voltage for the unbalanced output at 1kHz. The red/blue traces (left and right channels) represent the MM configuration, and purple/green (left and right channels ) for the MC configuration. For the MM configuration, THD values at 100mVrms are at 0.001%, then dip as low as 0.0001% around 1Vrms, then a slow rise to the “knee” just below 9Vrms. For the MC configuration, THD values at 100mVrms are at 0.005%, then steadily decrease down to near 0.0005% at 1Vrms. Above 1Vrms, for both MM and MC configurations, THD values are lower for the right channel compared to the left channel. The 1% THD values for the both inputs are reached at 9.8Vrms at the output. It’s important to mention that anything above 1-2Vrms is not typically required for most line-level preamps or integrated amps.
THD+N ratio (unweighted) vs output voltage at 1kHz - MM and MC inputs
Above we can see a plot of THD+N ratios as a function of output voltage for the unbalanced output at 1kHz. The red/blue traces (left and right channels) represent the MM configuration, and purple/green (left and right channels) for the MC configuration. For the MM configuration, THD+N values at 100mVrms are at 0.05%, then dip as low as 0.0006% between 5Vrms and the “knee” just below 9Vrms. For the MC input, THD+N values at 100mVrms are at 0.2%, then dip as low as 0.004% just before the “knee.”
THD+N ratio (A-weighted) vs output voltage at 1kHz - MM and MC inputs
Above we can see a plot of THD+N (A-weighted) ratios as a function of output voltage for the unbalanced output at 1kHz. The red/blue traces (left and right channels) represent the MM configuration, and purple/green (left and right channels) for the MC configuration. For the MM configuration, THD+N values at 100mVrms are at 0.01%, then dip as low as 0.0005/0.0002% (left/right) between 5Vrms and the “knee” just below 9Vrms. For the MC configuration, THD+N values at 100mVrms are at 0.07%, then dip as low as 0.003/0.001% (left/right) around the “knee.”
FFT spectrum, 1kHz - MM input
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sine-wave stimulus for the MM configuration, which results in the reference voltage of 1Vrms (0dBrA) at the unbalanced output. Here we see very clean results. Only the signal’s second harmonic (2kHz) is visible at -125dBrA, or 0.00006%. On the left side of the signal peak, there is a small 60Hz power supply fundamental peak at around -105/100dBrA (left/right), or 0.0006/0.001%. There are also very low-level peaks from the higher order odd harmonics of the power supply fundamental (e.g., 300, 420, 540, 660Hz, etc) at -110dBrA, or 0.0003%, and below.
FFT spectrum, 1kHz - MC input
Shown above is an FFT of a 1kHz input sine-wave stimulus for the MC configuration at the unbalanced output. As there is 20dB more gain with the MC setting, predictably the noise floor is elevated compared to the MM FFT above, although only by about 15dB. This is also a very clean FFT for a MC phono preamplifier. The signal and noise peak patterns are essentially the same as with the MM configuration, but about 15dB higher in amplitude.
FFT spectrum, 50Hz - MM input
Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the unbalanced output for the MM 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 harmonics from the 50Hz signal (100, 150, 200Hz, etc.) are non-existent above the noise floor, and the two power-supply related noise peaks can be seen most predominantly, but still at very low levels of below -110dBRa, or 0.0003%, at higher odd harmonics.
FFT spectrum, 50Hz - MC input
Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the balanced output for the MC 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 harmonics from the 50Hz signal (100, 150, 200Hz, etc.) are non-existent above the noise floor, and the two power-supply related noise peaks can be seen most predominantly, but still at low levels of below -90dBRa, or 0.003%, at higher odd harmonics.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MM input
Above is an FFT of the IMD products for an 18kHz and 19kHz summed sine-wave stimulus tone for the MM configuration measured at the balanced output. The input rms values are set so that if summed (for a mean frequency of 18.5kHz), would yield 0.5Vrms (reference or 0dBRa) at the output. Here we find the second order modulation product (i.e. the difference signal of 1kHz) at -85/90dBrA (left/right), or 0.006/0.003%. We can also see the third order modulation products (i.e. 17kHz and 20kHz) sitting at roughly -105dBrA, or 0.0006%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MC
The last chart is an FFT of the IMD products for an 18kHz and 19kHz summed sine-wave stimulus tone for the MC configuration. Here we find the second-order modulation product (i.e., the difference signal of 1kHz) is at -65/70dBrA (left/right), or 0.06/0.03%. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) at just above -100dBRa, or 0.001%.
Diego Estan
Electronics Measurement Specialist
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