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