Link: reviewed by Thom Moon on SoundStage! Access on July 15, 2021
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The AT-PEQ30 was conditioned for 30 minutes at 1Vrms at the output before any measurements were taken.
The AT-PEQ30 offers one pair of unbalanced RCA inputs and one pair of unbalanced RCA outputs. The input can be configured for a moving magnet (MM) or moving coil (MC) cartridge by selecting a switch on the front panel. To achieve the reference output voltage of 1Vrms at 1 kHz, 18mVrms was required with the MM setting, and 0.9mVrms with the MC setting.
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Audio-Technica for the AT-PEQ30 compared directly against our own measurements. The published specifications are sourced from Audio-Technica’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 output into 100k ohms, a measurement input bandwidth of 10Hz to 90kHz, and the worst-case measured result between the left and right channels.
Parameter | Manufacturer | SoundStage! Lab |
Gain (MM/MC) | 35/59dB | 34.8/60.8dB |
RIAA response accuracy (MM) | 20Hz-20kHz, ±0.5dB | 20Hz-20kHz, ±0.3dB |
RIAA response accuracy (MC) | 20Hz-20kHz, ±0.5dB | 20Hz-20kHz, +0.5/-0dB |
Rated Output | 250mV | N/A |
Input sensitivity (for rated output, MM/MC) | 4.5/0.28mV | 4.5/0.23mV |
Input impedance (MM/MC) | 47k/120 ohms | 41.2k/146 ohms |
SNR (MM/MC, ref 1Vrms, A-weighted) | 100/74dB | 102/75dB |
*SNR (MM/MC, ref 0.25Vrms, A-weighted) | 100/74dB | 90/63dB |
*Audio-Technica's SNR specifications (100/74dB for MM/MC) were not given with a reference output voltage, therefore, our SNR measurements are shown with both a 1Vrms output, and Audio-Technica's 250mVrms rated output.
Our primary measurements revealed the following using the unbalanced MM setting (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) | -95.6dB | -98.1dB |
DC offset | <-5mV | <-5mV |
Gain (default) | 35.0dB | 34.8dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-86dB | <-88dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-108dB | <-108dB |
Input impedance | 41.2k ohms | 44.0k ohms |
Maximum output voltage (at clipping 1% THD+N) | 2.94Vrms | 2.94Vrms |
Noise level (A-weighted) | <7uVrms | <7uVrms |
Noise level (unweighted) | <300uVrms | <300uVrms |
Output impedance | 684 ohms | 684 ohms |
Overload margin (relative 5mVrms input, 1kHz) | 20.51dB | 20.64dB |
Overload margin (relative 5mVrms input, 20Hz) | 1.1dB | 1.1dB |
Overload margin (relative 5mVrms input, 20kHz) | 39.28dB | 38.99dB |
Signal-to-noise ratio (A-weighted) | 102.3dB | 102.5dB |
Signal-to-noise ratio (unweighted) | 67.6dB | 67.8dB |
THD (unweighted) | <0.0001% | <0.0001% |
THD+N (A-weighted) | <0.0007% | <0.0007% |
THD+N (unweighted) | <0.03% | <0.03% |
Our primary measurements revealed the following using the unbalanced MC 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) | -83.6dB | -89.5dB |
DC offset | <-5mV | <-5mV |
Gain (default) | 60.8dB | 60.8dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <83dB | <83dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <83dB | <83dB |
Input impedance | 146 ohms | 146 ohms |
Maximum output voltage (at clipping 1% THD+N) | 2.94Vrms | 2.94Vrms |
Noise level (A-weighted) | <160uVrms | <160uVrms |
Noise level (unweighted) | <5mVrms | <5mVrms |
Output impedance | 684 ohms | 684 ohms |
Overload margin (relative 0.5mVrms input, 1kHz) | 14.64dB | 14.61dB |
Overload margin (relative 0.5mVrms input, 20Hz) | -4.4dB | -4.4dB |
Overload margin (relative 0.5mVrms input, 20kHz) | 34.42dB | 34.22dB |
Signal-to-noise ratio (A-weighted) | 74.9dB | 75.2dB |
Signal-to-noise ratio (unweighted) | 46.5dB | 46.0dB |
THD (unweighted) | <0.002% | <0.002% |
THD+N (A-weighted) | <0.017% | <0.017% |
THD+N (unweighted) | <0.4% | <0.4% |
Frequency response - MM input
Shown above is our frequency-response plot for the MM setting measured at the unbalanced output. 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 AT-PEQ30 is within +/-0.3dB or so of flat from 20Hz to 20kHz, meeting Audio-Technica’s claim of 20Hz-20kHz (+/-0.5dB). It is about -2dB down at 80kHz, and +1/1.5dB (left/right) at about 55kHz. The worst-case channel-to-channel deviation is between 5kHz and 20kHz, where the right channel is almost 0.5dB 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 setting, the AT-PEQ30 is within +0.5dB/-0dB or so of flat from 20Hz to 20kHz, meeting Audio-Technica’s of claim of 20Hz-20kHz (+/-0.5dB). We can see that the MM configuration offers a more extended low frequency bandwidth, where the MC configuration is at -2dB at 10Hz compared to the MM configuration that measured near 0dB at 10Hz. Channel-to-channel deviations can also be seen with the MC setting from 5kHz to 20kHz, but to a lesser degree compared to the MM setting, with about 0.2dB deviation.
Phase response - MM input
Above is the phase response of the AT-PEQ30 for the MM setting, from 20Hz to 20kHz. The AT-PEQ30 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 5-8kHz.
Phase response - MC input
Above is the phase response of the AT-PEQ30 for the MC setting, from 20Hz to 20kHz. The AT-PEQ30 does not invert polarity. Here we find a worst-case -65 degrees around 200Hz and 7-8kHz.
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 (L/R) traces represent the MM configured input, and purple/green for MC. For the MM configuration, THD values at 20Hz are at 0.004%, then dip as low as 0.00007% around 1-2kHz, then up to 0.003% at 20kHz. For the MC configuration, THD values at 20Hz are at 0.1%, then dip down to 0.0002% around 10kHz, then a climb to 0.0007% 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 unbalanced output. The red/blue (L/R) traces represent the MM configured input, and purple/green for MC. For the MM configuration, THD values at 100mVrms are at 0.0005%, then dip as low as 0.00007% between 0.8 and 1Vrms, then the “knee” around 2.5Vrms, where THD values reach 0.0002%. For the MC configuration, THD values at 100mVrms are at 0.01%, then steadily decrease down to 0.005% at the 2.5Vrms “knee.” The 1% THD values for the both inputs are reached at around 3Vrms 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. The red/blue (L/R) traces represent the MM-configured input, and purple/green for the MC-configured input For the MM configuration, THD+N values at 100mVrms are at 0.5%, then dip as low as 0.015% between 1 to 2.5Vrms, then the “knee” around 2.5Vrms. For the MC configuration, THD+N values at 100mVrms are at 3%, then dip as low as 0.15% around the 2.5Vrms “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. The red/blue (L/R) traces represent the MM configured input, and purple/green for MC. For the MM configuration, THD+N values at 100mVrms are at 0.006%, then dip as low as 0.0003% at the “knee” around 2.5Vrms. For the MC configuration, THD+N values at 100mVrms are at 0.15%, then dip as low as 0.006% around the 2.5Vrms “knee.”
FFT spectrum, 1kHz - MM input
Shown above is a fast Fourier transform (FFT) of a 1kHz input sine-wave stimulus for the MM setting, which results in the reference voltage of 1Vrms (0dBrA) at the unbalanced output. Here we see exceptionally clean results. Signal harmonics are just below -120dBrA (2kHz), or 0.0001%, and below. The first odd-order harmonic (3kHz) is just barely perceptible above the noise floor at -135dBrA, or 0.00002%. On the left side of the signal peak, there is perhaps just a hint of a 60Hz peak due to power-supply noise at -100dBrA, or 0.001%, and again at the third noise harmonic of 180Hz, at -115dBrA, or 0.0002%.
FFT spectrum, 1kHz - MC input
Shown above is an FFT of a 1kHz input sine-wave stimulus for the MC setting at the unbalanced output. As there is 25dB more gain with the MC setting, predictably, the noise floor is higher, and with this, there are no visible signal or noise harmonic peaks.
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 setting. 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 nonexistent above the noise floor, as are the power-supply noise peaks.
FFT spectrum, 50Hz - MC input
Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the unbalanced output for the MC setting. 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 nonexistent above the noise floor, as are the power-supply noise peaks.
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 setting measured at the unbalanced output. 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 just above -110dBRa, or 0.0003%. The fourth- and fifth-modulation products are also clearly visible.
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 setting. 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 just above -110dBRa, or 0.0003%. Unlike the MM setting however, with the MC setting, the fourth- and fifth-modulation products are not visible, likely due to the higher noise floor.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by James Hale on SoundStage! Xperience on July 1, 2021
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The iFi Audio Zen Phono was conditioned for 30 minutes at 1Vrms at the output before any measurements were taken.
The Zen Phono offers one pair of unbalanced RCA inputs, a pair of unbalanced RCA outputs, and a balanced output via a 4.4mm TRRS connector. The input can be configured for different moving magnet (MM) and moving coil (MC) cartridges via a small DIP switch on the back panel. A small white LED on the front panel indicates the selection: MM, MC High, MC Low, or MC Very Low. Also included is a subsonic filter, which can be activated using a button on the front panel.
I measured the performance of the Zen Phono for the following input configurations: MM, MC Low, MC Very Low. To achieve the reference output voltage of 1Vrms at 1 kHz, 15mVrms was required with the MM setting, 1mVrms with the MC Low setting, and 0.265mVrms with the MC Very Low setting. Other than the extra 6dB of gain and double the maximum output voltage, we found no differences between the balanced and unbalanced outputs, provided the balanced output was referenced to 2Vrms, and the unbalanced output to 1Vrms (i.e., THD, THD+N and signal-to-noise ratios (SNRs) were identical for the same input voltage).
Published specifications vs. our primary measurements
The table below summarizes the measurements published by iFi Audio for the Zen Phono compared directly against our own. The published specifications are sourced from iFi Audio’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth is set at its maximum (DC to 1MHz), assume, unless otherwise stated, 1Vrms output into 100k ohms (200k ohms balanced) and a measurement input bandwidth of 10Hz to 90kHz, and the worst-case measured result between the left and right channel.
Parameter | Manufacturer | SoundStage! Lab |
Gain (MM/MC High/MC Low/MC Very Low) | 36/48/60/72±1dB | 36.8/48.8/60.6/71.7dB |
RIAA response accuracy (MM, 10Hz to 100kHz) | ±0.4dB | +0.1dB/-2dB (10Hz/80kHz) |
RIAA response accuracy (MM, 20Hz to 20kHz) | ±0.15dB | ±0.05dB |
Channel separation (1kHz, all modes) | >75dB | >79dB |
Maximum output voltage (balanced, 100k ohm-load, 1% THD) | 20Vrms | 20.2Vrms |
Maximum output voltage (balanced, 600 ohm-load, 1% THD) | 13.5Vrms | 12.9Vrms |
Maximum output voltage (unbalanced, 600 ohm-load, 1% THD) | 6.5Vrms | 8Vrms |
Output impedance (balanced/unbalanced) | 200/100 ohms | 204/102 ohms |
Input impedance (MM/MC Low/MC Very Low) | 47k/1k/110 ohms | 48.1k/966/137 ohms |
SNR (MM/MC Low/MC Very Low, ref 1V, A-weighted) | 96/90/79dB | 89/85/73dB |
THD (MM/MC Low/MC Very Low, ref 1V) | 0.0003/0.01/0.005% | 0.0005/0.019/0.006% |
Our primary measurements revealed the following using the unbalanced MM setting (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) | -69.3dB | -72.6dB |
DC offset | <0.2mV | <0.2mV |
Gain (default) | 36.8dB | 36.8dB |
IMD ratio (18kHz + 19kHz stimulus tones) | <-76dB | <-77dB |
IMD ratio (3kHz + 4kHz stimulus tones) | <-96dB | <-96dB |
Input impedance | 48.1k ohms | 46.9k ohms |
Maximum output voltage (at clipping 1% THD+N) | 10.1Vrms | 10.1Vrms |
Noise level (A-weighted) | <32uVrms | <32uVrms |
Noise level (unweighted) | <200uVrms | <200uVrms |
Output impedance | 102 ohms | 102 ohms |
Overload margin (relative 5mVrms input, 1kHz) | 29.4dB | 29.4dB |
Overload margin (relative 5mVrms input, 20Hz) | 10.1dB | 10.1dB |
Overload margin (relative 5mVrms input, 20kHz) | 38.4dB | 38.4dB |
Signal-to-noise ratio (A-weighted) | 89.0dB | 89.2dB |
Signal-to-noise ratio (unweighted, 20Hz to 20kHz) | 79.7dB | 80.2dB |
THD (unweighted) | <0.0005% | <0.0005% |
THD+N (A-weighted) | <0.0031% | <0.0031% |
THD+N (unweighted) | <0.02% | <0.02% |
Our primary measurements revealed the following using the unbalanced MC Low setting (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) | -94.9dB | -70.6dB |
DC offset | <0.3mV | <0.3mV |
Gain (default) | 60.6dB | 60.7dB |
IMD ratio (18kHz + 19kHz stimulus tones) | <-33dB | <-34dB |
IMD ratio (3kHz + 4kHz stimulus tones) | <-58dB | <-59dB |
Input impedance | 966 ohms | 984 ohms |
Maximum output voltage (at clipping 1% THD+N) | 10.1Vrms | 10.1Vrms |
Noise level (A-weighted) | <51uVrms | <51uVrms |
Noise level (unweighted) | <240uVrms | <220uVrms |
Output impedance | 102 ohms | 102 ohms |
Overload margin (relative 0.5mVrms input, 1kHz) | 25.8dB | 25.8dB |
Overload margin (relative 0.5mVrms input, 20Hz) | 6.4dB | 6.4dB |
Overload margin (relative 0.5mVrms input, 20kHz) | 31.1dB | 31.1dB |
Signal-to-noise ratio (A-weighted) | 85.3dB | 85.4dB |
Signal-to-noise ratio (unweighted, 20Hz to 20kHz) | 78.3dB | 78.0dB |
THD (unweighted) | <0.019% | <0.017% |
THD+N (A-weighted) | <0.023% | <0.020% |
THD+N (unweighted) | <0.03% | <0.03% |
Our primary measurements revealed the following using the unbalanced MC Very Low setting (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) | -89.8dB | -73.1dB |
DC offset | <1mV | <1mV |
Gain (default) | 71.7dB | 71.7dB |
IMD ratio (18kHz + 19kHz stimulus tones) | <-47dB | <-48dB |
IMD ratio (3kHz + 4kHz stimulus tones) | <-71dB | <-72dB |
Input impedance | 137 ohms | 136 ohms |
Maximum output voltage (at clipping 1% THD+N) | 10.1Vrms | 10.1Vrms |
Noise level (A-weighted) | <190uVrms | <190uVrms |
Noise level (unweighted) | <800uVrms | <800uVrms |
Output impedance | 102 ohms | 102 ohms |
Overload margin (relative 0.25mVrms input, 1kHz) | 20.5dB | 20.5dB |
Overload margin (relative 0.25mVrms input, 20Hz) | 1.3dB | 1.3dB |
Overload margin (relative 0.25mVrms input, 20kHz) | 29.6dB | 29.6dB |
Signal-to-noise ratio (A-weighted) | 73.4dB | 73.3dB |
Signal-to-noise ratio (unweighted, 20Hz to 20kHz) | 66.0dB | 65.2dB |
THD (unweighted) | <0.006% | <0.006% |
THD+N (A-weighted) | <0.019% | <0.019% |
THD+N (unweighted) | <0.09% | <0.09% |
Frequency response RIAA - MM setting
In our measured frequency-response plot above for the MM setting measured at the unbalanced output, the Zen is within +/-0.1dB or so of flat from 5Hz to 50kHz, and about -2dB down at 80kHz, meeting iFi audio’s first claim of 20Hz-20kHz (+/-0.15dB), but not meeting the second claim of 10Hz-100kHz (+/-0.4dB). 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. In our results, the Zen Phono has essentially perfect RIAA accuracy from 5Hz to 50kHz. The purple/green (left/right) traces represent the frequency response with the subsonic filter engaged, where we see -3dB at around 5Hz. In the graph above and some of the graphs below, we see two visible traces: the left channel (blue, purple or pink trace) and the right channel (red, green or orange trace). 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 RIAA - MC Low and MC Very Low settings
In our measured frequency-response plot above for the MC Low/MC Very Low settings (they performed identically) measured at the unbalanced output, the Zen is within +/-0.1dB or so of flat from 20Hz to 20kHz, meeting iFi Audio’s first claim of 20Hz-20kHz (+/-0.15dB). We can see that the MM configuration offers a more extended bandwidth, where these MC configurations are at -1.5dB at 5Hz and -0.7dB at 50kHz. The purple/green (left/right) traces represent the frequency response with the subsonic filter engaged, where see a -3dB point at around 7Hz.
Phase response - MM, MC Low, and MC Very Low settings
Above is the phase response of the Zen for three input settings (they measured effectively identically) measured at the unbalanced output, from 20Hz to 20kHz. The purple/green traces represent the measured phase shift with the subsonic filter engaged. The Zen 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 -55 degrees at 5kHz. With the subsonic filter engaged, there’s a less than a 20 degree difference in phase shift at 20Hz.
THD ratio (unweighted) vs. frequency - MM, MC Low, and MC Very Low settings
The chart above shows THD ratio 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 (left/right) traces represent the MM configured input, purple/green MC Low, and pink/orange MC Very Low. For the MM configuration, THD values at 20Hz are at 0.005%, then dip as low as 0.0004% around 1kHz, then up to 0.003% at 20kHz. For the MC Low configuration, THD values at 20Hz are at 0.01%, then dip as low as 0.003% around 100Hz, then a steady climb to 0.3% at 20kHz. For the MC Very Low configuration, THD values at 20Hz are at around 0.04%, then dip as low as 0.004% between 500Hz and 1kHz, then up to 0.025% at 20kHz.
THD ratio (unweighted) vs. output voltage at 1kHz - MM, MC Low, MC Very settings
Above we can see a plot of THD ratios as a function of output voltage for the unbalanced output. The red/blue (left/right) traces represent the MM configured input, purple/green MC Low, and pink/orange MC Very Low. For the MM configuration, THD values at 100mVrms are at 0.003%, then dip as low as 0.0003% between 1 and 3Vrms, then the “knee” around 8-9Vrms, where THD values reach 0.003%. For the MC Low configuration, THD values at 100mVrms are at 0.005%, then steadily increase up to the 1% mark at 10Vrms, where THD vs. output values for all input configurations meet. For the MC Very Low configuration, THD values at 100mVrms are near 0.02%, then dip as low as 0.003% around 1Vrms, then the “knee” around 8-9Vrms, where THD values reach 0.03%. 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, MC Low, and MC Very Low settings
Above we can see a plot of THD+N ratios as a function of output voltage for the unbalanced output. The red/blue (L/R) traces represent the MM configured input, purple/green MC Low, and pink/orange MC Very Low. For the MM configuration, THD+N values at 100mVrms are at 0.15%, then dip as low as 0.002% between 6 to 8Vrms, then the “knee” around 9Vrms. For the MC Low configuration, THD+N values at 100mVrms are at 0.2%, then dip as low as 0.03% around 1Vrms, then rise steadily to the “knee” near 10Vrms, where the 1%THD+N values can be seen. For the MC Very Low configuration, THD+N values at 100mVrms are at around 0.7%, then dip as low as 0.02% between 3 to 5Vrms, then the “knee” around 9Vrms, where THD+N sits at 0.03%.
FFT spectrum, 1kHz - MM setting
Shown above is a fast Fourier Transform (FFT) of a 1kHz input sinewave stimulus for the MM setting, which results in the reference voltage of 1Vrms at the unbalanced output. Here we see exceptionally clean results. Signal harmonics are at -120dBrA or 0.0001% and below. The odd order harmonics (i.e., 3kHz, 5kHz) are slightly higher in amplitude than the 2kHz even order second harmonic. On the left side of the signal peak, there are no peaks due to power supply noise above the noise floor, which ranges from -90dBrA, at 20Hz to -120dBrA at 1kHz.
FFT spectrum, 1kHz - MC Low setting
Shown above is an FFT of a 1kHz input sinewave stimulus for the MC Low setting at the unbalanced output. The 2kHz second-order signal harmonic peak is at -75dBrA, or 0.02%%, while the 3kHz third-order harmonic is at -85dBrA, or 0.006%. On the left side of the signal peak, we see the power-supply noise fundamental peak (60Hz) at -90/-85dBrA (L/R) or 0.003/0.006%, and just barely above the noise floor, we see the second- and third-harmonic noise peaks (120Hz, 180Hz), just above -100dBrA, or 0.001%.
FFT spectrum, 1kHz - MC Very Low setting
Shown above is an FFT of a 1kHz input sinewave stimulus for the MC Very Low setting at the unbalanced output. Despite the extra gain compared to the MC Low setting, this setting yields far less distortion, although predictably, with a higher noise floor. The 2kHz second-order signal harmonic peak is at -90dBrA, or 0.003%, while the 3kHz third-order harmonic is practically nonexistent. On the left side of the signal peak, we see the power-supply noise fundamental peak (60Hz) at -75/-70dBrA (left/right), or 0.02/0.03%, and just barely above the noise floor, we see the second and third harmonic noise peaks (120Hz, 180Hz), right around -90dBrA, or 0.003%.
FFT spectrum, 50Hz - MM setting
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the unbalanced output for the MM setting. 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 nonexistent above the noise floor, as are the power-supply noise peaks.
FFT spectrum, 50Hz - MC Low setting
The chart above is the FFT for a 50Hz input sinewave stimulus measured at the unbalanced output for the MC Low setting. The second harmonic from the 50Hz signal (100Hz) is at -90dBrA, or 0.003%, so right around the same level as the 60Hz noise peak (left channel). Subsequent signal harmonics cannot be seen above the noise floor.
FFT spectrum, 50Hz - MC Very Low setting
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the unbalanced output for the MC Very Low setting. The harmonics from the 50Hz signal cannot be seen above the noise floor, while the 60Hz noise peak is again visible at -75/-70dBrA (left/right), or 0.02/0.03%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MM setting
Above is an FFT of the IMD products for an 18kHz and 19kHz summed sinewave stimulus tone for the MM setting measured at the unbalanced output. 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 -85dBrA, or 0.006%. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) sitting at -110/-105dBRa (left/right), or 0.0003/0.0006%. The fourth and fifth modulation products are also clearly visible.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MC Low setting
This chart is an FFT of the IMD products for an 18kHz and 19kHz summed sinewave stimulus tone for the MC Low setting. Here we find the second-order modulation product (i.e., the difference signal of 1kHz) is quite high at -40dBrA, or 1%. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) are also high, at -50dBRa, or 0.3%. These IMD FFTs are reflected in our simplified IMD results (which only account for the sum of the second- and third-order modulation products) in our primary measurement table, where the MM setting measured a respectable -76dB, or 0.015%, but the MC Low setting yielded only -33dB, or 0.02%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MC Very Low setting
This chart is an FFT of the IMD products for an 18kHz and 19kHz summed sinewave stimulus tone for the MC Very Low setting. Here we find the second-order modulation product (i.e., the difference signal of 1kHz) at around -55dBrA, or 0.2%. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) are much lower, at -75dBRa, or 0.02%.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Jason Thorpe on SoundStage! Hi-Fi on May 15, 2021
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The iPhono3 was conditioned for 30 minutes at 1Vrms at the output before any measurements were taken.
The iPhono3 has one switch and one unbalanced pair of RCA outputs on one end, while the other end has two pairs of unbalanced RCA inputs for connection of a moving-magnet (MM) or moving-coil (MC) cartridge. The switch allows the user to select between RIAA, Columbia, and Decca EQ settings. There are a number of DIP switches underneath, allowing the user to alter MC resistive loading, MM capacitive loading, gain, and variations on EQ (i.e., enhanced RIAA and standard with and without subsonic filter).
For the MM input, capacitive loading was set to 100pF and the gain set to 36dB, which required a 16.2mVrms 1kHz sinewave to achieve the reference output voltage. For the MC input, resistive loading was set to 100 ohms and the gain set to 60dB, which required a 1.18mVrms 1kHz sinewave to achieve the reference output voltage
Published specifications vs. our primary measurements
The table below summarizes the measurements published by iFi Audio for the iPhono3 Black Label compared directly against our own. The published specifications are sourced from iFi Audio’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth is 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.
Parameter | Manufacturer | SoundStage! Lab |
Input impedance (MC) | 100 ohms | 119 ohms |
RIAA response accuracy (MM, 10Hz to 100kHz) | ±0.3dB | -0.2dB, +2dB |
RIAA response accuracy (MM, 20Hz to 20kHz) | ±0.2dB | -0.2dB, +0.7dB |
Dynamic range (MM, max output, A-weighted) | >108dB | 106dB |
Dynamic range (MC, max output, A-weighted) | >106dB | 94dB |
Signal-to-noise ratio (MM, ref 5mV, A-weighted) | >85dB | 80dB |
Signal-to-noise ratio (MC, ref 0.5mV, A-weighted) | >85dB | 71dB |
Overload margin (MM, ref 5mV, 1kHz @ 1%THD) | >26dB | 26dB |
Overload margin (MC, ref 0.5mV, 1kHz @ 1%THD) | >22dB | 23.3dB |
Crosstalk (MM, 1kHz) | <-71dB | 71dB |
Maximum output voltage (load=600 ohms, 1% THD) | 7Vrms | 6.1Vrms |
THD (MM, 1Vrms out @1kHz, 600 ohms load) | <0.005% | 0.012% |
Output impedance | 100 ohms | 102 ohms |
Our primary measurements revealed the following using the unbalanced MM input (unless specified, assume a 1kHz sinewave, 1Vrms output in 100k ohms, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -65dB | -80dB |
DC offset | 400uV | 900uV |
Gain (default) | 35.84dB | 35.84dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-70dB | <-70dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-69dB | <-69dB |
Input impedance | 45.9k ohms | 48.5k ohms |
Maximum output voltage (at clipping 1% THD+N) | 6.1Vrms | 6.1Vrms |
Noise level (A-weighted) | <29uVrms | <29uVrms |
Noise level (unweighted) | <140uVrms | <140uVrms |
Output impedance | 102 ohms | 101 ohms |
Overload margin (relative 5mVrms input, 1kHz) | 26.0dB | 26.0dB |
Overload margin (relative 5mVrms input, 20Hz) | 3.3dB | 3.3dB |
Overload margin (relative 5mVrms input, 20kHz) | 44.6dB | 44.9dB |
Signal-to-noise ratio (A-weighted) | 90dB | 90dB |
Signal-to-noise ratio (unweighted, 20Hz to 20kHz) | 78dB | 78dB |
THD (unweighted) | <0.011% | <0.012% |
THD+N (A-weighted) | <0.013% | <0.014% |
THD+N (unweighted) | <0.018% | <0.018% |
Our primary measurements revealed the following using the unbalanced MC input (unless specified, assume a 1kHz sinewave, 1Vrms output into 100k ohms, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -66dB | -98dB |
DC offset | 2mV | 1mV |
Gain (default) | 53.3dB | 53.2dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-34dB | <-34dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-59dB | <-59dB |
Input impedance | 119 ohms | 119 ohms |
Maximum output voltage (at clipping 1% THD+N) | 6Vrms | 6Vrms |
Noise level (A-weighted) | <116uVrms | <117uVrms |
Noise level (unweighted) | <1300uVrms | <1200uVrms |
Output impedance | 102 ohms | 101 ohms |
Overload margin (relative 0.5mVrms input, 1kHz) | 23.3dB | 23.3dB |
Overload margin (relative 0.5mVrms input, 20Hz) | 0.83dB | 0.83dB |
Overload margin (relative 0.5mVrms input, 20kHz) | 39dB | 39dB |
Signal-to-noise ratio (A-weighted) | 78dB | 78dB |
Signal-to-noise ratio (unweighted, 20Hz to 20kHz) | 58dB | 58dB |
THD (unweighted) | <0.022% | <0.023% |
THD+N (A-weighted) | <0.028% | <0.027% |
THD+N (unweighted) | <0.13% | <0.12% |
Frequency response RIAA - MM input
In our measured frequency-response plot above for the MM input, the iPhono3 is at worst +0.7dB (left channel) or so of flat from 20Hz to 20kHz, not quite meeting iFi’s claim of +/-0.2dB. 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 claim of +/-0.3dB from 10Hz to 100kHz was also not corroborated by our measurements, where at 80kHz, the MM input was at about +2dB. In the graph above and some of the graphs below, we see two visible traces; the left channel (blue or purple trace) and the right channel (red or green trace). 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 RIAA - MC input
In our measured frequency-response plot above for the MC input, the iPhono3 is at worst +0.7dB (left channel) or so of flat from 20Hz to 20kHz, not quite meeting iFi’s claim of +/-0.2dB. The claim of +/-0.3dB from 10Hz to 100kHz was also not corroborated by our measurements, where at 80kHz, the MC input was at about -2.5dB.
Frequency response for RIAA, Columbia, and Decca settings - MM input (no EQ applied to input sweep)
Above is the raw (no EQ applied in the Audio Precision generator) frequency response of the iPhono3 using the RIAA (blue), Columbia (green) and Decca (burgundy) EQ settings for the MM input with a 0.5mVrms sinewave input swept from 10Hz to 80kHz (the results for the MC input were effectively identical). We find deviations of about 5 dB at 20Hz, and 3dB at 20kHz between all three EQ settings.
Phase response - MM and MC inputs
Above is the phase response of the iPhono3 for both the MM and MC inputs (they measured effectively identically), from 20Hz to 20kHz. 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 6kHz. Because the worst case is -60 degrees, that indicates that the iPhono3 does not invert polarity.
THD ratio (unweighted) vs. frequency - MM input
Above is the THD ratio as a function of frequency chart for the MM input, where the input sweep is EQ’d with an inverted RIAA curve. The output voltage is maintained at the reference 1Vrms. Since iFi provides specs for 600-ohm loading, here we show data for a typical 100k ohms load (blue/red), and for a 600 ohms load (purple/green). The iPhono3 performed identically with either load. The THD values vary from 0.01% at 20Hz, down to below 0.001% from 100Hz to 200Hz, then back up just above 0.02% from 2kHz to 20kHz.
THD ratio (unweighted) vs. frequency - MC input
Above is the THD ratio as a function of frequency chart for the MC input. The output voltage is maintained at the refrence 1Vrms. Since iFi provides specs for 600 ohm loading, here we show data for a typical 100k ohms load (blue/red), and for a 600 ohms load (purple/green). The THD values vary from 0.1% at 20Hz, down to 0.004% at around 100Hz, then a steady near linear climb to 0.3% at 20kHz.
THD ratio (unweighted) vs. output voltage at 1kHz (input voltage from 1mVrms to 100mVrms) - MM input
Above is the chart of THD ratio as a function of output voltage for the MM input. We can see very low THD ratio values, ranging from as low as 0.002% at 150mVrms, up to about 0.06% at 4Vrms. Beyond this point there is sharp rise in THD. The 1% THD ratio value is reached at 6Vrms at the output.
THD+N ratio (unweighted) vs. output voltage at 1kHz (input voltage from 1mVrms to 100mVrms) - MM input
Above we can see the plot of THD+N ratio as a function of output voltage for the MM input. We can see THD+N ratio values ranging from 0.2% at around 50mVrms, down to about 0.02% at 1Vrms.
THD ratio (unweighted) vs. output voltage at 1kHz (input voltage from 0.1mVrms to 12mVrms) - MC input
Above is the THD ratio as a function of output voltage for the MC input. The MC input behaved almost identically to the MM input, with the lowest THD values recorded also around 150mVrms, at around 0.004%.
THD+N ratio (unweighted) vs. output voltage at 1kHz (input voltage from 0.1mVrms to 12mVrms) - MC input
Above we can see the plot of THD+N ratio as a function of output voltage for the MC input. We can see THD+N ratio values ranging from 1.5% at around 50mVrms, down to about 0.05% between 2 and 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 output voltage of 1Vrms. Here we see that the third signal harmonic at 3kHz is close to -75dB below the reference signal, or at -75dBrA, equivalent to 0.02%. The second harmonic at 2kHz is non-existent. The frequency components on the left side of the 1kHz peak are mostly due to power supply noise, where the typical 60Hz and 120Hz peaks can be seen. The worst noise peak (60Hz) is at around -80dBrA, or 0.01%, with the subsequent harmonic (120Hz) at around -90dBrA, or 0.003%. The third (180Hz) and fourth (240Hz) harmonics are just above -100dBrA, or 0.001%.
FFT spectrum, 1kHz - MC input
Shown above is the FFT of a 1kHz input sinewave stimulus for the MC input. Here we see that the second and third signal harmonics (2 and 3kHz) are close to -75dBrA, or 0.02%. The 60Hz peak is at -60dBrA, or 0.1%; the second noise harmonic (120Hz) is close to -70dBrA, or 0.03%; and the third (180Hz) and fourth (240Hz) harmonics are just above -80dBrA, or 0.01%.
FFT spectrum, 50Hz - MM input
Shown above is the FFTs for a 50Hz input sinewave stimulus measured at the output 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 harmonic of the 50Hz signal (100Hz) is non-existent. What dominate are the power supply noise peaks, which were described in the 1kHz FFT above.
FFT spectrum, 50Hz - MC input
Shown above is the FFTs for a 50Hz input sinewave stimulus for the MC input. The second harmonic of the 50Hz signal (100Hz) is at -90dBrA, or 0.003%. What dominate are the power supply noise peaks, which were described in the 1kHz FFT above.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MM input
Shown 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 almost -100dBrA, or 0.001%. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) measure at around -85dBrA, or 0.006%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MC input
This chart shows 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) at around -40dBrA, or 1%. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) are also considerably different between the MM and MC inputs, where the MM peaks measure at around -85dBrA, or 0.006%, and the MC peaks are just under -50dBrA, or 0.3%. These differences are reflected in our simplified IMD results (which only account for the sum of the second- and third-order modulation products) in our primary measurement table, where the MM input outperformed the MC input by 36dB.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Jason Thorpe on SoundStage! Hi-Fi on January 15, 2021
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The V10 was conditioned for 30 minutes at 1Vrms at the output before any measurements were taken.
The V10 offers one pair of unbalanced RCA outputs and one pair of balanced XLR outputs, as well as two pairs of unbalanced RCA inputs, one pair for moving-magnet (MM) and the other for a moving-coil (MC) cartridge. There are a number of DIP switches on the rear panel of the V10, allowing the user to alter MC resistive loading, MM capacitive loading, and gain, as well to turn on or off a subsonic filter. Other than the 6dB difference in gain between the balanced and unbalanced outputs (+6dB for balanced), there were no mentionable differences between both outputs types in terms of THD+N, as long as the gain was kept constant. Settings were left at the manufacturer’s default positions (see specs below). To achieve the reference output voltage of 1Vrms at 1kHz at the balanced output, 10mVrms was required at the MM input and 1mVrms at the MC input.
Published specifications vs. our primary measurements
The tables below summarize our primary measurements performed on the V10. Here we can compare directly against Hegel’s own published specifications for the V10, which are stated as follows:
Our primary measurements revealed the following using the unbalanced MM input (unless specified, assume a 1kHz sinewave, 1Vrms at the balanced output into a 200k ohms load, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -82.6dB | -82.6dB |
DC offset | -10mV | -13mV |
Gain (default) | 40.23dB | 40.12dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-92dB | <-92dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-92dB | <-92dB |
Input impedance | 46.8k ohms | 46.2k ohms |
Maximum output voltage (at clipping 1% THD+N) | 24Vrms | 24Vrms |
Noise level (A-weighted) | <56uVrms | <56uVrms |
Noise level (unweighted) | <300uVrms | <300uVrms |
Output impedance | 200.3 ohms | 199.9 ohms |
Overload margin (relative 5mVrms input, 1kHz) | 33.4dB | 33.4dB |
Overload margin (relative 5mVrms input, 20Hz) | 14.3dB | 14.3dB |
Overload margin (relative 5mVrms input, 20kHz) | 53.1dB | 53.1dB |
Signal-to-noise ratio (A-weighted) | 84.4dB | 84.8dB |
Signal-to-noise ratio (unweighted, 20Hz to 20kHz) | 76.1dB | 76.5dB |
THD (unweighted) | <0.0008% | <0.0008% |
THD+N (A-weighted) | <0.005% | <0.005% |
THD+N (unweighted) | <0.03% | <0.03% |
Our primary measurements revealed the following using the unbalanced MC input (unless specified, assume a 1kHz sinewave, 1Vrms at the balanced output into a 200k ohms load, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10 kHz) | -88.0dB | -95.1dB |
DC offset | -10mV | -13mV |
Gain (default) | 59.87dB | 59.77dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-76dB | <-73dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-89dB | <-89dB |
Input impedance | 124.0 ohms | 124.3 ohms |
Maximum output voltage (at clipping 1% THD+N) | 24Vrms | 24Vrms |
Noise level (A-weighted) | <108uVrms | <108uVrms |
Noise level (unweighted) | <600uVrms | < 600uVrms |
Output impedance | 200.3 ohms | 199.9 ohms |
Overload margin (relative 0.5mVrms input, 1kHz) | 33.8dB | 33.8dB |
Overload margin (relative 0.5mVrms input, 20Hz) | 14.6dB | 14.6dB |
Overload margin (relative 0.5mVrms input, 20kHz) | 53.6dB | 53.6dB |
Signal-to-noise ratio (A-weighted) | 78.8 dB | 78.9dB |
Signal-to-noise ratio (unweighted, 20Hz to 20kHz) | 66.3dB | 66.4dB |
THD (unweighted) | <0.001% | <0.001% |
THD+N (A-weighted) | <0.01% | <0.01% |
THD+N (unweighted) | <0.07% | <0.09% |
Gain was measured at 40 and 60dB (Balanced, MM/MC), the same as Hegel’s spec. The MC load input impedance was measured at 124 ohms, closely matching Hegel’s spec and setting of 100 ohms. The input impedance for the MM input was measured at 47 and 46k ohms (L/R), very close to the industry standard 47k ohms.
Output noise (A-weighted) was measured at -85dB (MM) and -79dB (MC), either exceeding or approaching Hegel’s specs of -84/-81dB (MM/MC). Our measured output impedance of 200 ohms confirmed Hegel’s spec of the same value.
Our measured crosstalk values at 10kHz were close to Hegel’s spec of -84dB (at 1kHz), where we measured -83dB for both channels for the MM input and -88/-95dB (left and right channels) for the MC input. For a direct comparison, we also measured crosstalk at 1kHz, and found -98/-100dB (L/R channels, MM input), and -88/-90dB (L/R channels, MC input), bettering the -84dB Hegel spec.
Hegel’s claim of better than 0.005% (MM) and 0.009% (MC) THD was also verified. There are many ways to measure THD, and manufacturers are often shy on showing all of the parameters used for the measurement. Here, we assume that Hegel is referring to THD (not THD+N), unweighted, against a 1Vrms 1kHz output signal. The bandwidth for Hegel’s measurement is unknown, but we use 10Hz to 90kHz for our measurements. Under those conditions, we found the V10’s THD to be below 0.0008% (MM) and 0.001% (MC). Even if Hegel’s THD spec is actually THD+N (A-weighted), they still meet spec for the MM input, as we measured 0.005%, and come very close for the MC input at 0.01%.
Hegel’s maximum output voltage (1% THD+N) claim of 23Vrms (balanced) was also confirmed, where we measured 24Vrms.
Frequency response - MM input
The blue (left channel) and red (right channel) traces represent the frequency response without the subsonic filter turned on. In our measured frequency-response plot above for the MM input, the V10 is within +/-0.2dB or so of flat from 20Hz to 20kHz, just about meeting Hegel’s RIAA accuracy claim of +/-0.1dB. 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 V10 has nearly perfect RIAA accuracy from 5Hz to 80kHz. The purple (left channel) and green (right channel) traces represent the frequency response with the subsonic filter engaged, where Hegel’s claim of -3dB at 20Hz is confirmed. In the graph above and some of the graphs below, we see two visible traces; the left channel (blue or purple trace) and the right channel (red or green trace). 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 - MC input
In our measured frequency-response plot above for the MC input shown with the blue and red traces (left and right channels), the V10 is within +/-0.2dB or so of flat from 20Hz to 20kHz, just about meeting Hegel’s RIAA accuracy claim of +/-0.1dB. The worst-case deviation was seen at around 8Hz, were the V10 over-responded by 0.5dB. The purple and green trace (left and right channels) represent the frequency response with the sub-sonic filter engaged, where Hegel’s claim of -3dB at 20Hz is confirmed.
Phase response - MM and MC inputs
Above is the phase response of the V10 for both the MM and MC inputs (they measured effectively identically), from 20Hz to 20kHz. The V10 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 -55 degrees at 5kHz.
THD ratio (unweighted) vs. frequency - MM input
The chart above shows THD ratio as a function of frequency for the MM input, where the input sweep is EQ’d with an inverted RIAA curve. The output voltage is maintained at the refrence 1Vrms. The THD values vary from 0.01% at 20Hz, down to below 0.0001% at 10kHz, then back up just above 0.0003% at 20kHz.
THD ratio (unweighted) vs. frequency - MC input
The chart above shows THD ratio as a function of frequency for the MM input, where the input sweep is EQ’d with an inverted RIAA curve. The THD values vary from 0.04% at 20Hz, down to around 0.0004% at 5kHz, then a climb to 0.001% at 20kHz.
THD ratio (unweighted) vs. output voltage at 1kHz (input voltage from 1mVrms to 30mVrms) - MM input
Above we can see a plot of THD ratios as a function of output voltage for the MM input. We can see very low THD ratio values, ranging from as low as 0.0001% at 5Vrms, up to about 0.0006% at the “knee”, just past 20Vrms, and about 0.005% at the lowest output voltage of 100mVrms. Beyond the “knee” there is sharp rise in THD as the V10 reaches its maximum output voltage. 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 (input voltage from 1mVrms to 100mVrms) - MM input
Above we can see a plot of THD+N ratios as a function of output voltage for the MM input. We can see THD+N ratio values, ranging from 0.2% at 100Vrms, down to about 0.0015% between 15 and 20Vrms.
THD ratio (unweighted) vs. output voltage at 1kHz (input voltage from 0.1mVrms to 30mVrms) - MC input
Above we can see a plot of THD ratios as a function of output voltage for the MC input. The MC input behaved similarly to the MM input, with 0.007% THD at 100mVrms, dipping to the lowest THD value of 0.0005% at 2Vrms, then up just past 0.003% at the knee at 20Vrms. The 1% THD ratio value is reached at 24Vrms at the output.
THD+N ratio (unweighted) vs. output voltage at 1kHz (input voltage from 0.1mVrms to 30mVrms) - MC input
Above we can see a plot of THD+N ratios as a function of output voltage for the MC input. We can see THD+N ratio values ranging from around 0.5% at 100Vrms, down to about 0.005% between 15 and 20Vrms.
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 output voltage of 1Vrms. Here we see exceptionally clean results. Signal harmonics are non-existent (i.e., cannot be seen above the -120dB noise floor at 2kHz). The frequency components on the left side of the 1kHz peak are mostly due to power-supply noise, where the typical 60Hz and 120Hz peaks can be seen. The worst noise peak (60Hz) is below -80dBrA, with the subsequent harmonic (120Hz) at around -90dBrA. The third harmonic (180Hz) is just below -90dBrA, and the subsequent harmonics are below -100dBrA.
FFT spectrum, 1kHz - MC input
Shown above is the FFT of a 1kHz input sinewave stimulus for the MC input. Signal harmonics are virtually non-existent, only a hint of a peak can be seen below -110dB at 2kHz. The 60Hz and 120Hz peaks are just below -70dBrA, and the third and fourth noise harmonics are just below -80dBrA.
FFT spectrum, 50Hz - MM input
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output 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 harmonics from the 50Hz signal (100, 150, 200Hz, etc) are non-existent. The power supply noise peaks can clearly be seen, which were described in the 1kHz FFT chart above.
FFT spectrum, 50Hz - MC input
Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output for the MC input. Like the MM FFT, here again, the harmonics from the 50Hz signal (100, 150, 200Hz, etc.) are non-existent. The power-supply noise peaks can clearly be seen, which were described in the 1kHz FFT above.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MM input
The chart 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) just above -100dBrA. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) are extremely low, below -120dBRa.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MC input
The next chart 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) just at -80dBrA, which is very low. We can also see the third-order modulation products (i.e., 17kHz and 20kHz) are extremely low, below -120dBRa. These clean IMD FFTs are reflected in our simplified IMD results (which only account for the sum of the second- and third-order modulation products) in our primary measurement table, where the MM input measured at -92dB for both channels and the MC input at -76/-73dB, for, respectively, the left and right channels. Incidentally, the 3dB difference between left and right channels for the MC input can be seen in the 1kHz peak in the FFT chart above. The fourth-order modulation products are non-existent in this FFT and the one for the MM input.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Doug Schneider on SoundStage! Hi-Fi on January 1, 2021
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The Bellari VP549 was conditioned for 30 minutes at 1Vrms at the output before any measurements were taken.
The VP549 is designed for moving-magnet (MM) cartridges only and has one set of single-ended RCA inputs and outputs. There are two switches and one knob on the front panel of the VP549. One switch selects between 120pF, 220pF, and 330pF cartridge-loading capacitance. The other switch, Rumble Filter, enables a low-frequency filter that provides attenuation below 20Hz. The knob controls the preamp’s overall gain. The center position is labelled “0,” the minimum position “-10dB,” and the maximum position “+4dB.” Unless otherwise stated, measurements were performed with the cartridge load capacitance set to 220pF, the Rumble Filter switch disengaged, and the gain set to the default “0” position. An 8mVrms 1kHz sinewave was required to achieve the reference output voltage of 1Vrms.
Published specifications vs. our primary measurements
The table below summarizes our primary measurements performed on the VP549. Here we can compare directly against Bellari’s own published specifications for the VP549, which are stated as follows:
Our primary measurements revealed the following (unless specified, assume a 1kHz sinewave, 1Vrms output into 100k ohms, 10Hz to 90kHz bandwidth, gain set to 0):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -49.1dB | -52.5dB |
DC offset | -10mV | -9mV |
Gain (default, 0dB) | 42.6dB | 42.2dB |
Gain (minimum, -10dB) | 32.1dB | 31.8dB |
Gain (maximum, +4dB) | 46.5dB | 46.5dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-90dB | <-90dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-91dB | <-91dB |
Input impedance | 47.8k ohms | 46.9k ohms |
Maximum output voltage (at clipping 1% THD+N) | 3.95Vrms | 3.95Vrms |
Noise level (A-weighted) | <70uVrms | <64uVrms |
Noise level (unweighted) | <4500uVrms | <4500 uVrms |
Output impedance | 460.5 ohms | 460.8 ohms |
Overload margin (relative 5mVrms input, 1kHz) | 15.3dB | 15.8dB |
Overload margin (relative 5mVrms input, 20Hz) | -0.2dB | 0.5dB |
Overload margin (relative 5mVrms input, 20kHz) | 35.4dB | 36.3dB |
Signal-to-noise ratio (A-weighted) | 82.9dB | 82.9dB |
Signal-to-noise ratio (unweighted, 20Hz to 20kHz) | 60.3dB | 60.3dB |
Signal-to-noise ratio (gain at -10dB, A-weighted) | 92.4dB | 92.4dB |
Signal-to-noise ratio (gain at +4dB, A-weighted) | 78.6dB | 78.7dB |
THD (unweighted) | <0.0012% | <0.0012% |
THD+N (A-weighted) | <0.0063% | <0.0063% |
THD+N (unweighted) | <0.4% | <0.4% |
THD+N (gain at -10dB, A-weighted) | <0.0025% | <0.0025% |
THD+N (gain at -10dB, unweighted) | <0.15% | <0.15% |
THD+N (gainm at +4dB, A-weighted) | <0.01% | <0.01% |
THD+N (gain at +4dB, unweighted) | <0.4% | <0.4% |
Our measured input (47.8/46.9k ohms, L/R) and output (460.5/460.8 ohms, L/R) impedances match very closely Bellari’s specs of 47k ohms and 470 ohms. Our measured gain values at all three settings also corroborate the published specifications, with maximum deviations in the order of 2-3%.
For the remainder of the specifications, as is often the case with manufacturer supplied measurements, not enough information is given to directly reproduce their results. With respect to Bellari’s THD of 0.005%, the company has not specified a reference output voltage, gain setting, weighting, or bandwidth filter. Our THD measurement shows an even lower <0.0012% (unweighted) against a 1Vrms output voltage, whereas our THD+N figure (A-weighted) is <0.0063% for both channels.
Bellari’s signal-to-noise ratio (SNR) of >94dB (unweighted) seems generous, however, again, we have very little information provided with respect to measurement parameters. The most charitable SNR measurement we could achieve was with the gain setting at -10dB and the output voltage at 1.35 Vrms (1 kHz), where we measured 95dB (A-weighted). Our reference SNR measurement (1Vrms output, gain set to 0) is 83dB (A-weighted), or 60dB (unweighted, input bandwidth filter set from 20Hz to 20kHz).
Frequency response
The chart above shows our frequency response measurement. 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 blue and red curves are the left and right channel without the Rumble Filter switch engaged, the green and purple curves with the Rumble Filter switch engaged. The measurement was also made with the gain set to its minimum and maximum values, and with every cartridge load capacitance setting, which had no effect on the frequency-response results. We can see here that Bellari’s claim of +/-1dB is valid at the top end of the spectrum (up to 23kHz as stated), but the +/-1dB claim down to 14Hz was not corroborated by our measurement. We find a -5.3dB dip at 30Hz, and at 14Hz, down -5.5dB again. In the graph above and some of the graphs below, we see two visible traces; the left channel (blue or purple trace) and the right channel (red or green trace). 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.
Phase response
Shown above is the phase response from 20Hz to 20kHz. The VP549 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 +20 degrees at 20Hz, and just below -60 degrees between 5 and 10kHz.
THD ratio (unweighted) vs. frequency
The chart above is the THD ratio 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 THD values vary from 0.05% at 20Hz, down to below 0.001% at 1kHz, then back up to 0.007% at 20kHz.
THD ratio (unweighted) vs. output voltage at 1kHz (input voltage from 1mVrms to 100mVrms)
Above we can see a plot of THD ratio as a function of output voltage. We can see very low THD ratio values, ranging from 0.005% at 100mVrms down to below 0.001% at around 1Vrms at the output, then a sharp rise in THD at the “knee” at around 3.5Vrms at the output. Beyond this output voltage, the VP549 distortion begins to rise exponentially. The 1% THD ratio value is reached at around 4Vrms 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 (input voltage from 1mVrms to 100mVrms)
Above we can see a plot of THD+N ratio as a function of output voltage. At 100mVrms, THD+N values are at around 3%, then down to between 0.1 and 0.2% at 3Vrms. There is a considerable difference in the THD+N vs. THD plots for the VP549, where it’s clear that distortion products are low, but noise, as shown in this chart, is relatively high.
FFT spectrum, 1kHz
Shown above is a fast Fourier transform (FFT) of a 1kHz 8mVrms input sinewave stimulus, which results in the reference output voltage of 1Vrms with the gain set to 0. Here we see that the second harmonic at 2kHz is <-100dB below the reference signal (dBrA). The frequency components on the left side of the 1kHz peak are mostly due to power supply noise. Of note is the peak at 60Hz at a level near -70dBrA.
FFT spectrum, 50Hz
The chart above is an FFT of a 50Hz input sinewave stimulus, which results in the reference output voltage of 1Vrms with the gain set to 0. 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 no perceptible signal harmonic peaks (e.g., 100Hz, 150Hz) above the relatively high noise floor. The highest noise peak is from the primary source (60Hz) at about -75dBrA, while the next highest peak is from the third harmonic noise peak (180Hz) at about -85dBrA.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus)
This final chart shows an FFT of the IMD products for an 18kHz and 19kHz summed sinewave stimulus tone. 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. Although it appears that the second-order modulation product (i.e., the difference signal of 1kHz) is sitting at -105dBrA, the peak is actually at 1020Hz, which is the 17th harmonic from the 60Hz power-supply noise. The 1kHz IMD peak is imperceptible above the noise floor. The third-order modulation products (i.e., 17kHz and 20kHz) are just above -110dBra, and the subsequent modulation products are not noticeable.
Diego Estan
Electronics Measurement Specialist
Links: reviewed by Doug Schneider on SoundStage! Hi-Fi on January 1, 2021 and by James Hale on SoundStage! Xperience on January 1, 2021
General information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The NAD PP 2e was conditioned for 30 minutes at 1Vrms at the output before any measurements were taken.
On the PP 2e’s back panel are one switch, to switch between moving-magnet (MC) and moving-coil (MC) operation, and two sets of single-ended RCA inputs, with one set labeled MC and the other set MM. The rear panel also has a pair of single-ended RCA outputs. For the MM input, a 15mVrms 1kHz sinewave was required to achieve the reference output voltage of 1Vrms, while a 1.2mVrms 1kHz sinewave was required at the MC input.
Published specifications vs. our primary measurements
The tables below summarize our primary measurements performed on the PP 2e. Here we can compare directly against NAD’s own published specifications for the PP 2e, which are stated as follows:
Our primary measurements below revealed the following using the unbalanced MM input (unless specified, assume a 1kHz sinewave, 1Vrms output into 100k ohms load, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -84.9dB | -87.0dB |
DC offset | -3.3mV | -3.0mV |
Gain (default) | 37.1dB | 37.0dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-69dB | <-84dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-80dB | <-96dB |
Input impedance | 47.65k ohms | 47.81k ohms |
Maximum output voltage (at clipping 1% THD+N) | 5.32Vrms | 5.32Vrms |
Noise level (A-weighted) | <22uVrms | <22uVrms |
Noise level (unweighted) | <100uVrms | <100uVrms |
Output impedance | 521.8 ohms | 522.1 ohms |
Overload margin (relative 5mVrms input, 1kHz) | 23.5dB (75.1mVrms) | 23.6dB (75.7mVrms) |
Overload margin (relative 5mVrms input, 20Hz) | 4.48dB (8.4mVrms) | 4.35dB (8.3Vrms) |
Overload margin (relative 5mVrms input, 20kHz) | 43.1dB (711mVrms) | 43.1dB (711mVrms) |
Signal-to-noise ratio (A-weighted) | 92.6dB | 92.5dB |
Signal-to-noise ratio (unweighted, 20Hz to 20kHz) | 83.3dB | 84.9dB |
THD (unweighted) | <0.0018% | <0.0014% |
THD+N (A-weighted) | <0.0026% | <0.0024% |
THD+N (unweighted) | <0.011% | <0.011% |
Our primary measurements below revealed the following using the unbalanced MC input (unless specified, assume a 1kHz sinewave, 1Vrms output into 100k ohms load, 10Hz to 90kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz) | -81.5dB | -80.4dB |
DC offset | -3.3mV | -3.0mV |
Gain (default) | 59.1dB | 59.0dB |
IMD ratio (18kHz and 19kHz stimulus tones) | <-73dB | <-78dB |
IMD ratio (3kHz and 4kHz stimulus tones) | <-79dB | <-89dB |
Input impedance | 123.3 ohms | 123.4 ohms |
Maximum output voltage (at clipping 1% THD+N) | 5.32Vrms | 5.32Vrms |
Noise level (A-weighted) | <64uVrms | <64uVrms |
Noise level (unweighted) | <400uVrms | <400uVrms |
Output impedance | 521.8 ohms | 522.1 ohms |
Overload margin (relative 0.5mVrms input, 1kHz) | 21.5dB (6mVrms) | 21.6dB (6mVrms) |
Overload margin (relative 0.5mVrms input, 20Hz) | 2.54dB (0.67mVrms) | 2.42dB (0.66mVrms) |
Overload margin (relative 0.5mVrms input, 20kHz) | 41.1dB (56.5Vrms) | 41.1dB (56.5Vrms) |
Signal-to-noise ratio (A-weighted) | 83.8dB | 83.5dB |
Signal-to-noise ratio (unweighted, 20Hz to 20kHz) | 76.6dB | 76.5dB |
THD (unweighted) | <0.0021% | <0.0017% |
THD+N (A-weighted) | <0.0061% | <0.0061% |
THD+N (unweighted) | <0.05% | <0.05% |
Our measured input impedances for both the MM (47.65/47.81k ohms) and MC inputs (117.6/118.6 ohms) match very closely NAD’s specs of 47k ohms and 100 ohms.
Our measured gain values for both inputs (MM: 37dB, MC: 59dB) also corroborate the published specifications of 35dB and 60dB. Input sensitivity is another way to express gain (in volts per volts). Interestingly, NAD’s input sensitivity specs when converted to dB are 38dB for the MM input and 56.5dB for the MC input, which are slightly different than their specs for gain. Nevertheless, all published gain values are very close to our measured values.
NAD’s signal-to-noise ratio (SNR) specs of 80dB and 78dB (MM and MC, A-weighted) are difficult to compare to our measured values, because we do not know what NAD used as a reference output voltage. Nevertheless, our measured values of 93dB and 84dB (MM and MC, A weighted, with a 1Vrms reference) exceed those published by NAD.
NAD’s maximum output voltage value of 5.3mVrms was corroborated by our measurements, where we saw 1% THD+N at 5.32Vrms at the output (1kHz).
Our input overload values are expressed in dB, as overload margin, with a reference 5mVrms and 0.5mVrms input signal for the MM and MC inputs respectively. We measured the input signals required at 20Hz, 1kHz, and 20kHz to achieve 5.32Vrms at the output for both input types. We expressed those values in dB as a ratio over the reference values (5 and 0.5Vrms), but we also show the actual input voltages in parentheses so as to directly compare against the NAD values. We measured lower input overload values; with some rounding, our values compare to NADs as follows: 8/75/711 vs. 10/102/950mVrms for the MM input, and 0.7/6/57 vs. 0.9/8/84Vrms for the MC input.
NAD’s published rated distortion values are <0.03% for both input types; unfortunately, we only know these were measured with a 20Hz to 20kHz filter. We don’t know if NAD measured THD or THD+N, and what they used as a reference output voltage. Our measured THD+N values of about 0.003% and 0.006% (MM and MC) show better performance than the published values, but these are A-weighted. We also measured THD+N ratios with a 20Hz to 20kHz bandwidth (instead of A-weighting), using the fourth-order low-/high-pass Butterworth filters in the APx555, and measured less than 0.008% for the MM input, and less than 0.03% for the MC input, corroborating NAD’s claim.
In terms of our measured output impedance, there is a significant discrepancy, where we measured about 522 ohms vs. NAD’s published 100 ohms. While 500 ohms is on the high side for a line level device output impedance, it should pose no issues for any typical active preamp or integrated amp input.
Frequency response - MM and MC inputs
In the measured frequency-response plot (above), the PP 2e is within 0.3dB of flat from 20Hz to 20kHz, corroborating the NAD claim. We found the same measured response with both the MM and MC input. 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. In the graph above and some of the graphs below, we see two visible traces; the left channel (blue or purple trace) and the right channel (red or green trace). 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.
Phase response - MM and MC inputs
Above is the phase response of the PP 2e for both the MM and MC inputs (they measured effectively identically), from 20Hz to 20kHz. The PP 2e 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 +28 degrees at 20Hz, and just above -60 degrees between 200 and 300Hz, and right around -60 degrees between 5 and 8kHz.
THD ratio (unweighted) vs. frequency - MM input
This is the THD ratio as a function of frequency plot for the MM input, where the input sweep is EQ’d with an inverted RIAA curve. The output voltage is maintained at the refrence 1Vrms. The THD values vary from 0.005% at 20Hz, down to below 0.001% from 300Hz to 500Hz, then back up just above 0.01% at 20kHz. One curiosity is the deviation in THD between left and right channels, where we find up to 5dB difference in favor of the right channel, which is most obvious between 1 and 5kHz.
THD ratio (unweighted) vs. frequency - MC input
Above is the THD ratio as a function of frequency for the MC input. The THD values vary from 0.01% at 20Hz, down to just above 0.001% at around 500Hz, then back up just above 0.01% at 20kHz. Here again, we see a deviation in THD between left and right channels.
THD ratio (unweighted) vs. output voltage at 1kHz (input voltage from 1mVrms to 100mVrms) - MM input
Above is the THD ratio as a function of output voltage plot for the MM input. We can see very low THD ratio values ranging from just above 0.01% down to 0.001% at around 2Vrms at the output, then to a sharp rise in THD at the “knee” at just shy of 5Vrms at the output. The deviation in THD performance (5-10dB) in favor of the right channel can be seen with output voltages between 1 and 5Vrms. The 1% THD ratio value is reached at 5.32Vrms 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 (input voltage from 1mVrms to 100mVrms) - MM input
Above is the THD+N ratio as a function of output voltage plot for the MM input. We can see THD+N ratio values ranging from just above 0.1% below 100mVrms, down to 0.002% (R) and 0.005% (L) at around 3-4Vrms at the output.
THD ratio (unweighted) vs. output voltage at 1kHz (input voltage from 1mVrms to 100mVrms) - MC input
Above is the THD ratio as a function of output voltage plot for the MC input. THD ratio values range from about 0.015% at 100mVrms to 0.001% at around 2Vrms at the output, then to a sharp rise in THD at the “knee” at just shy of 5Vrms at the output. Beyond this output voltage, the DUT distortion begins to rise exponentially. The 1% THD ratio value is reached at 5.32Vrms at the output.
THD+N ratio (unweighted) vs. output voltage at 1kHz (input voltage from 1mVrms to 100mVrms) - MC input
The chart above is the THD+N ratio as a function of output voltage plot for the MC input. We can see THD+N ratio values ranging from just above 0.2% below 100mVrms, down to between 0.005% and 0.01% at around 3-4Vrms at the output.
FFT spectrum, 1kHz - MM input
Shown above is a fast Fourier transform (FFT) of a 1kHz 15mVrms input sinewave stimulus for the MM input, which results in the reference output voltage of 1Vrms. Here we see that the second signal harmonic at 2kHz is at -100dBrA (L) and -105dBRa (R). At 3kHz, or the third signal harmonic, we see at 10dB difference between the left (-100dBrA) and right (-110dBrA) channels. The worst noise peak is at 120Hz (second harmonic of 60Hz) and can be seen at around -90dBrA (left) and -100dBrA (right).
FFT spectrum, 1kHz - MC input
Above is a fast Fourier transform (FFT) of a 1kHz 1.2mVrms input sinewave stimulus for the MC input. The second (2kHz) and third (3kHz) signal harmonics are roughly the same here as with the MM input above. The worst noise peaks are at around -90dBrA at 180Hz (third harmonic of 60Hz) and just below -80dBrA at 60Hz. Of note, is that the 120Hz predominates on the MM input, while on the MC input, it’s the 60Hz peak.
FFT spectrum, 50Hz - MM input
The chart above depicts a fast Fourier transform (FFT) of 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. Here we see that the second noise harmonic at 120Hz dominates at -90dBrA (L) and -100dBRa (R). The second signal harmonic (100Hz) is at -100dBrA.
FFT spectrum, 50Hz - MC input
Above is a fast Fourier transform (FFT) of a 50Hz input sinewave stimulus for the MC input. Here we see that the thrid noise harmonic at 180Hz dominates at -80dBrA (L) and -90dBRa (R). The second signal harmonic (100Hz) is barely perceptible above the noise floor at -95dBrA.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MM input
The chart above represents 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 -95dBrA, which puts them a little below the primary power supply noise products. The third-order modulation products (i.e., 17kHz and 20kHz) are considerably different between the right and the left channels. This is also reflected in our simplified IMD results (which only accounts for the sum of the second and third order modulation products) in our primary measurement table, where the right channel outperformed the left by 15dB on the MM input, and by 5dB on the MC input. The worst-case third-order modulation product peaks are at about -85dBrA for the left channel, but closer to -105dBrA for the right channel.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus) - MC input
Above 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 at -85dBrA. The third-order modulation products (i.e., 17kHz and 20kHz) are at about -85dBrA for the left channel, but closer to -105dBrA for the right channel.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Dennis Burger on SoundStage! Simplifi on April 1, 2024
General Information
All measurements were conducted using an Audio Precision APx555 B Series analyzer.
The CD 50n was evaluated as a fixed-output DAC and conditioned for 30 minutes at 0dBFS (2.3Vrms out) into 100k ohms before any measurements were taken.
The CD 50n offers three digital inputs: one coaxial S/PDIF (RCA), one optical S/PDIF (TosLink), and one USB. There are two sets of unbalanced (RCA) line-level outputs (fixed and variable) and one headphone output (1/4″ TRS). There is an analog volume control for the headphone output.
The CD 50n offers a few features and settings. The following are the default settings used for the coaxial input, unbalanced line-level outputs, using a 0dBFS input, unless otherwise specified:
The analyzer’s input bandwidth filter was set to 10Hz–22.4kHz for all measurements, except for frequency response (DC to 1 MHz), FFTs (10Hz to 90kHz). and THD vs. Frequency (10Hz to 90kHz), with the latter to capture the second and third harmonics of the 20kHz output signal.
The CD 50n analog volume control for the headphone outputs appears to be a potentiometer. Channel-to-channel deviation proved typical for this type of volume control implementation.
Volume-control accuracy (measured at the headphone output): left-right channel tracking
Volume position | Channel deviation |
min | 0.73dB |
10% | 0.281dB |
30% | 0.769dB |
50% | 0.024dB |
70% | 0.188dB |
80% | 0.361dB |
90% | 0.329dB |
max | 0.052dB |
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Marantz for the CD 50n compared directly against our own. The published specifications are sourced from Marantz’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 as set at its maximum (DC to 1MHz), assume, unless otherwise stated, assume a fixed 2.34Vrms output (RCA) 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.
Parameter | Manufacturer | SoundStage! Lab |
THD (1kHz 0dBFS, 24/96) | <0.001% | <0.0005% |
Frequency response (24/192) Filter 1 | 2Hz-50kHz (-3dB) | 2Hz-64kHz (-3dB) |
Dynamic range (A-weighted, 24/96) | 112dB | 122dB |
Channel separation (1kHz 0dBFS) | 110dB | 138dB |
Our primary measurements revealed the following using the coaxial input and the single-ended line-level outputs (unless specified, assume a 1kHz sinewave at 0dBFS, 100k ohms loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz, 16/44.1) | -118.7dB | -123.6dB |
Crosstalk, one channel driven (10kHz, 24/96) | -116.5dB | -132.1dB |
DC offset | <-1.8mV | <-1.6mV |
Dynamic range (A-weighted, 16/44.1) | 96.4dB | 96.3dB |
Dynamic range (20Hz-20kHz, 16/44.1) | 94.9dB | 95.0dB |
Dynamic range (A-weighted, 24/96) | 122.5dB | 122.9dB |
Dynamic range (20Hz-20kHz, 24/96) | 119.8dB | 120.6dB |
IMD ratio (CCIF, 18kHz and 19kHz stimulus tones, 1:1, 16/44.1) | <-103dB | <-104dB |
IMD ratio (CCIF, 18kHz and 19kHz stimulus tones, 1:1, 24/96) | <-108dB | <-109dB |
IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1, 16/44.1) | <-90dB | <-91dB |
IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1, 24/96) | <-98dB | <-99dB |
Maximum output voltage | 2.34Vrms | 2.33Vrms |
Output impedance | 95 ohms | 95 ohms |
Noise level (with signal, A-weighted, 16/44.1) | <35uVrms | <35uVrms |
Noise level (with signal, 20Hz-20kHz, 16/44.1) | <43uVrms | <43uVrms |
Noise level (with signal, A-weighted, 24/96) | <2.7uVrms | <2.4uVrms |
Noise level (with signal, 20Hz-20kHz, 24/96) | <3.3uVrms | <2.9uVrms |
Noise level (no signal, A-weighted) | <1.73uVrms | <1.67uVrms |
Noise level (no signal, 20Hz-20kHz) | <2.3uVrms | <2.1uVrms |
THD ratio (unweighted, 16/44.1) | <0.0006% | <0.0005% |
THD+N ratio (A-weighted, 16/44.1) | <0.0016% | <0.0016% |
THD+N ratio (unweighted, 16/44.1) | <0.0019% | <0.0019% |
THD ratio (unweighted, 24/96) | <0.00049% | <0.00031% |
THD+N ratio (A-weighted, 24/96) | <0.00055% | <0.00037% |
THD+N ratio (unweighted, 24/96) | <0.00052% | <0.00034% |
Our primary measurements revealed the following using the coaxial input and the headphone output (unless specified, assume a 1kHz sinewave at 0dBFS, 300 ohms loading, 10Hz to 22.4kHz bandwidth, gain set to High):
Parameter | Left channel | Right channel |
Gain (High) | 14.27Vrms/FS | 14.35Vrms/FS |
Gain (Mid) | 6.17Vrms/FS | 6.14Vrms/FS |
Gain (Low) | 2.23Vrms/FS | 2.22Vrms/FS |
Maximum output (1% THD+N, 100k ohm load) | 7.63Vrms | 7.59Vrms |
Maximum output power into 600 ohms (1% THD+N, unweighted) | 74mW | 74mW |
Maximum output power into 300 ohms (1% THD+N, unweighted) | 120mW | 120mW |
Maximum output power into 32 ohms (1% THD+N, unweighted) | 147mW | 147mW |
Output impedance (all gain settings) | 67 ohms | 67 ohms |
Noise level (with signal, A-weighted, 16/44.1) | <31uVrms | <31uVrms |
Noise level (with signal, 20Hz-20kHz, 16/44.1) | <37uVrms | <37uVrms |
Noise level (with signal, A-weighted, 24/96) | <5.8uVrms | <6.0uVrms |
Noise level (with signal, 20Hz-20kHz, 24/96) | <7.2uVrms | <7.5uVrms |
Noise level (no signal, A-weighted, volume min) | <3.1uVrms | <3.2uVrms |
Noise level (no signal, 20Hz-20kHz, volume min) | <4.2uVrms | <4.6uVrms |
Dynamic range (A-weighted, 16/44.1, max output 6Vrms) | 96.4dB | 96.4dB |
Dynamic range (A-weighted, 24/96, max output 6Vrms) | 119.5Vrms | 119.7Vrms |
THD ratio (unweighted, 16/44.1) | <0.0052% | <0.0063% |
THD+N ratio (A-weighted, 16/44.1) | <0.0062% | <0.0075% |
THD+N ratio (unweighted, 16/44.1) | <0.0055% | <0.0066% |
THD ratio (unweighted, 24/96) | <0.0053% | <0.0064% |
THD+N ratio (A-weighted, 24/96) | <0.0061% | <0.0073% |
THD+N ratio (unweighted, 24/96) | <0.0053% | <0.0064% |
Frequency response vs. sample rate (16/44.1, 24/96, 24/192, Filter 1)
The plot above shows the CD 50n’s frequency response as a function of sample rate. The blue/red traces are for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz, the purple/green traces are for a 24/96 dithered digital input signal from 5Hz to 48kHz, and finally orange/pink represents 24/192 from 5Hz to 96kHz. The behavior at low frequencies is the same for the digital input—perfectly flat down to 5Hz. The behavior at high frequencies for all three digital sample rates is that of a shallow reconstruction filter (Filter 2 offers brickwall-type filtering). The -3dB point for each sample rate is roughly 17.5, 36.6, and 64.5kHz, respectively. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue, purple, or orange trace) is performing identically to the right channel (red, green, or pink trace), and so they perfectly overlap, indicating that the two channels are ideally matched.
Frequency response vs. filter setting (16/44.1)
The plots above show frequency response for a 0dBFS input signal sampled at 44.1kHz for Filter 1 (blue) and Filter 2 (red), into a 100k-ohm load for the left channel only. The graph is zoomed in from 1kHz to 22kHz to highlight the various responses of the filters. We can see that Filter 1 offers soft attenuation around the corner frequency, likely minimizing phase shift, with a -3dB point at 17.5 kHz, while Filter 2 is a brickwall-type filter, with a -3dB point at 20.9kHz. It’s worth pointing out that Filter 1 (the default filter) may be discernible with 16/44.1 content when compared to DACs with ruler-flat frequency responses using brickwall filters, depending on one’s age and high-frequency hearing acuity. The -1dB point is at roughly 12.5kHz.
Phase response (8-ohm loading, line-level input)
Above are the phase-response plots from 20Hz to 20kHz for the coaxial input, measured across at the unbalanced output, using both Filter 1 (blue) and Filter 2 (red) for a 16/44.1 input. We can see that the CD 50n does not invert polarity, with a worst-case phase shift of -80 degrees at 20kHz for Filter 2 (the brickwall filter). What Filter 1 loses in high-frequency response, it gains with zero phase shift in the audioband.
Digital linearity (16/44.1 and 24/96 data)
The graph above shows the results of a linearity test for the coaxial digital input (the optical input performed identically) for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the unbalanced line-level output of the CD 50n. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response is a straight flat line at 0dB (i.e., the amplitude of the digital input perfectly matches the amplitude of the measured analog output). The 24/96 input data is essentially perfect down to -120dBFS, while the 16/44.1 input data performed well, only overresponding by 2.5/2dB (left/right) at -120dBFS. The 24/96 data yielded such superb results that we extended the sweep down to . . .
-140dBFS. Above we see that even at -140dBFS, the CD 50n is only overshooting by 1dB with a 24/96 signal (right channel, the left is still at 0dB). This is an exemplary linearity test result.
Impulse response (24/44.1 data, Filter 1 and Filter 2)
The graph above shows the impulse responses for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s), for one sample period then back to digital silence, fed to the coaxial digital input, measured at the unbalanced outputs into a 100k-ohm load for the left channel only. Filter 1 is blue and Filter 2 is red. We can see that Filter 1 is a simple filter with virtually no pre/post ringing. Filter 2 shows almost no pre-ringing, but significant post-ringing.
J-Test (coaxial, Lock Range Wide)
The plot above shows the results of the J-Test test for the coaxial digital input measured at the unbalanced line-level output of the CD 50n, using the Wide Lock Range setting. J-Test was developed by Julian Dunn in the 1990s. It is a test signal—specifically, a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (i.e., 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sinewave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (e.g., 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA (fundamental at 250Hz) down to -170dBrA for the odd harmonics. The test file can also be used in conjunction with artificially injected sinewave jitter by the Audio Precision, to also show how well the DAC rejects jitter.
The coaxial input shows a good J-Test result, with two peaks at the -130dBrA level clearly flanking the 12kHz primary peak. This is an indication that the CD 50n may have good jitter immunity with the Wide setting.
J-Test (coaxial, Lock Range Wide, 100ns)
The plot above shows the results of the J-Test test for the coaxial digital input measured at the unbalanced line-level output, with an additional 100ns of 2kHz sinewave jitter injected by the APx555, which would manifest as sideband peaks at 10kHz and 14kHz without perfect jitter immunity. The results show visible sidebands at 10kHz and 14kHz, but at a very low -130dBrA. This is further evidence of the CD 50n’s strong jitter immunity using the Wide Lock Range setting.
J-Test (coaxial, Lock Range Narrow)
The plot above shows the results of the J-Test test for the coaxial digital input measured at the unbalanced line-level output of the CD 50n using the Narrow Lock Range setting. The result is identical to the Wide Lock Range setting.
J-Test (coaxial, Lock Range Narrow, 100ns)
The plot above shows the results of the J-Test test for the coaxial digital input measured at the unbalanced line-level output, with an additional 100ns of 2kHz sinewave jitter injected by the APx555, which would manifest as sideband peaks at 10kHz and 14kHz, without perfect jitter immunity. The result is very poor, with a significant increase in the noise floor. The Narrow Lock Range setting should not be used with sources that may be prone to jitter.
J-Test (coaxial, Lock Range Medium)
The plot above shows the results of the J-Test test for the coaxial digital input measured at the unbalanced line-level output of the CD 50n using the Medium Lock Range setting. The result is identical to the Wide and Narrow Lock Range settings.
J-Test (coaxial, Lock Range Medium, 100ns)
The plot above shows the results of the J-Test test for the coaxial digital input measured at the unbalanced line-level output, with an additional 100ns of 2kHz sinewave jitter injected by the APx555, which would manifest as sideband peaks at 10kHz and 14kHz, without perfect jitter immunity. The results show visible sidebands at 10kHz and 14kHz, but at an extremely low -145dBrA. This is evidence of the CD 50n’s very strong jitter immunity using the Medium Lock Range setting.
J-Test (optical, Lock Range Wide)
The plot above shows the results of the J-Test test for the optical digital input measured at the unbalanced line-level output of the CD 50n. The optical input is clearly worse than the coaxial input using the Wide Lock Range setting, with peaks as high as -105dBrA flanking the 12kHz fundamental.
J-Test (optical, Lock Range Wide, 100ns)
The plot above shows the results of the J-Test test for the optical digital input measured at the unbalanced line-level output, with an additional 100ns of 2kHz sinewave jitter injected by the APx555, which would manifest as sideband peaks at 10kHz and 14kHz without perfect jitter immunity. The results show visible sidebands at 10kHz and 14kHz, at a significant -80dBrA. This shows that the Wide Lock Range setting on the CD 50n should not be used with the optical input if the source is prone to jitter.
J-Test (optical, Lock Range Narrow)
The plot above shows the results of the J-Test test for the optical digital input measured at the unbalanced line-level output of the CD 50n using the Narrow Lock Range setting. The result is identical to the Wide Lock Range setting for the coax input.
J-Test (optical, Lock Range Narrow, 100ns)
The plot above shows the results of the J-Test test for the optical digital input measured at the unbalanced line-level output, with an additional 100ns of 2kHz sinewave jitter injected by the APx555, which would manifest as sideband peaks at 10kHz and 14kHz without perfect jitter immunity. The result is very poor, with a significant increase in the noise floor. As with the coaxial input, the Narrow Lock Range setting should not be used with sources that may be prone to jitter.
J-Test (optical, Lock Range Medium)
The plot above shows the results of the J-Test test for the optical digital input measured at the unbalanced line-level output of the CD 50n using the Medium Lock Range setting. The result is identical to the wide Lock Range setting for the coax input.
J-Test (optical, Lock Range Medium, 100ns)
The plot above shows the results of the J-Test test for the optical digital input measured at the unbalanced line-level output, with an additional 100ns of 2kHz sinewave jitter injected by the APx555, which would manifest as sideband peaks at 10kHz and 14kHz without perfect jitter immunity. The results show visible sidebands at 10kHz and 14kHz, but at an extremely low -145dBrA. This is evidence of the CD 50n’s very strong jitter immunity using the Medium Lock Range setting. For the optical input, this should be the preferred setting for sources that are prone to jitter.
Wideband FFT spectrum of white noise and 19.1kHz sine-wave tone (coaxial input, Filter 1)
The plot above shows a fast Fourier transform (FFT) of the CD 50n’s unbalanced-line level output with white noise at -4 dBFS (blue/red) and a 19.1 kHz sinewave at 0dBFS fed to the coaxial digital input, sampled at 16/44.1 (purple/green), using the Filter 1 filter. There is a soft roll-off above 20kHz as the white-noise spectrum shows. There are low-level aliasing artifacts in the audioband at -120dBrA at 6 and 13kHz. The primary aliasing signal at 25kHz is barely suppressed at -10dBrA.
Wideband FFT spectrum of white noise and 19.1kHz sine-wave tone (coaxial input, Filter 2)
The plot above shows a fast Fourier transform (FFT) of the CD 50n’s unbalanced line-level output with white noise at -4 dBFS (blue/red) and a 19.1 kHz sinewave at 0dBFS fed to the coaxial digital input, sampled at 16/44.1 (purple/green), using the Filter 2 filter. There is a steep roll-off above 20kHz in the white-noise spectrum due to the brick-wall filter. There are absolutely no imaged aliasing artifacts in the audioband above the -135dBrA noise floor. The primary aliasing signal at 25kHz is at -80dBrA.
THD ratio (unweighted) vs. frequency vs. load (24/96)
The chart above shows THD ratios at the unbalanced line-level output into 100k ohms (blue/red) and 600 ohms (purple/green) as a function of frequency for a 24/96 dithered 1kHz signal at the coaxial input. The 100k and 600 ohms data are very close throughout the audioband, with only a 5dB increase in THD at 20kHz into the 600-ohm load. The right channel outperformed the left channel by roughly 5dB throughout. THD ratios into 100k ohms (right channel) ranged from 0.0003% from 20Hz to 5kHz, then up to 0.0005% at 20kHz.
THD ratio (unweighted) vs. frequency vs. sample rate (16/44.1, 24/96)
The chart above shows THD ratios at the unbalanced line-level output into 100k ohms as a function of frequency for a 16/44.1 (blue/red) and a 24/96 (purple/green) dithered 1kHz signal at the coaxial input. THD ratios are roughly equivalent between the 16/44.1 and 24/96 data, roughly between 0.0003 and 0.0005%, with the same 5dB increase in THD between right and left channels seen in the previous graph.
THD ratio (unweighted) vs. output (16/44.1, 24/96)
The chart above shows THD ratios measured at the unbalanced output as a function of output voltage for the coaxial input into 100k ohms from -90dBFS to 0dBFS at 16/44.1 (blue/red) and 24/96 (purple/green). The 24/96 outperformed the 16/44.1 data at lower levels due to the increased noise floor with the lower 16-bit depth data (the analyzer cannot assign a THD ratio for peaks that do not manifest above the measured noise floor). For the 16/44.1 data, THD ratios ranged from 2% at 200uVrms, down to just below 0.0005% at the maximum output voltage of 2.34Vrms. The 24/96 THD ratios ranged from 0.1% at 200uVrms, down to the same 0.0005% at the maximum output voltage.
THD+N ratio (unweighted) vs. output (16/44.1, 24/96)
The chart above shows THD+N ratios measured at the unbalanced output as a function of output voltage for the coaxial input into 100k ohms from -90dBFS to 0dBFS at 16/44.1 (blue/red) and 24/96 (purple/green). The 24/96 outperformed the 16/44.1 data due to the increase noise floor with the lower 16-bit depth data. For the 16/44.1 data, THD+N ratios ranged from 20% at 200 uVrms, down to just 0.002% at the maximum output voltage of 2.34Vrms. The 24/96 THD+N ratios ranged from 1% at 200uVrms, down to 0.0005% at the maximum output voltage.
Intermodulation distortion vs. generator level (SMPTE, 60Hz:4kHz, 4:1, 16/44.1, 24/96)
The chart above shows intermodulation distortion (IMD) ratios measured at unbalanced output for 16/44.1 (blue/red) and 24/96 input data (purple/green), from -60dBFS to 0dBFS, for the coaxial input. Here, the SMPTE IMD method was used, where the primary frequency (F1 = 60Hz) and the secondary frequency (F2 = 7kHz) are mixed at a ratio of 4:1. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 16/44.1 data yields IMD ratios from 2% down to 0.002% at 0dBFS. The 24/96 data yields IMD ratios from 0.1% down to 0.0005% from -10 to -5dBFS, then up to 0.001% at 0dBFS.
FFT spectrum – 1kHz, 16/44.1 at 0dBFS
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the unbalanced output into 100k ohms for the coaxial digital input, sampled at 16/44.1. We see signal harmonics dominate at the second (2kHz) and third (3kHz) position at roughly -110dBrA, or 0.0003%, but also visible at lower levels up to and beyond 20kHz. There is only one small power-supply noise peak—the left channel at 120Hz at -130dBFS, or 0.00003%.
FFT spectrum – 1kHz, 24/96 at 0dBFS
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the unbalanced output into 100k ohm for the coaxial digital input, sampled at 24/96. Due to the increased bit depth, the noise floor is much lower compared to the 16/44.1 FFT at a very low -150 to -160dBrA. We see signal harmonics ranging from -110dBrA to -150dBrA, or 0.0003% to 0.000003%, all the way to 20kHz (and beyond). Here again, the second (2kHz) and third (3kHz) signal harmonics dominate at roughly -110dBrA. We find power-supply-related noise peaks at the second (120Hz), fourth (240Hz), and eighth (480Hz) harmonics, at -130dBrA to -140dBrA, or 0.00003% to 0.00001%.
FFT spectrum – 1kHz, 16/44.1 at -90dBFS
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the unbalanced output into 100k ohm for the coaxial digital input, sampled at 16/44.1 at -90dBFS. We see the signal peak at the correct amplitude, and no signal harmonics above the noise floor within the audioband.
FFT spectrum – 1kHz, 24/96 at -90dBFS
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the unbalanced output into 200k ohm for the coaxial digital input, sampled at 24/961 at -90dBFS. We see the signal peak at the correct amplitude, no signal harmonics, and the same power-supply-related noise peaks as seen in the 24/96 0dBFS FFT above.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, 16/44.1)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the unbalanced output into 100k ohms for the coaxial input at 16/44.1. The input dBFS values are set at -6.02dBFS so that, if summed for a mean frequency of 18.5kHz, would yield 2.34Vrms (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%, and the third-order modulation products, at 17kHz and 20kHz, are at -130dBrA, or 0.00003%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, 24/96)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the unbalanced output into 100k ohms for the coaxial input at 24/96. The input dBFS values are set at -6.02dBFS so that, if summed for a mean frequency of 18.5kHz, would yield 2.34Vrms (0dBrA) at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz), is at -120dBrA, or 0.0001%, and the third-order modulation products, at 17kHz and 20kHz, are at -125dBrA, or 0.00006%.
Intermodulation distortion FFT (coaxial input, APx 32 tone, 24/96)
Shown above is the FFT of the unbalanced line-level output of the CD 50n with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBFS reference, and corresponds to 2.34Vrms into 100k ohms. The intermodulation products—i.e., the “grass” between the test tones—are distortion products from the amplifier and below the -140dBrA, or 0.00001%, level. This is a very clean IMD result.
Diego Estan
Electronics Measurement Specialist
Link: reviewed by Roger Kanno on SoundStage! Hi-Fi on March 1, 2024
General Information
All measurements taken using an Audio Precision APx555 B Series analyzer.
The Magnetar UDP900 was evaluated as a DAC and was conditioned for 30 minutes at 0dBFS (1.95Vrms RCA out) into 100k ohms before any measurements were taken. But as mentioned below, the headphone output was also measured.
The UDP900 is a universal 4k UHD Blu-ray player. It offers one digital input (asynchronous USB) allowing for its evaluation as a DAC. It is important to note that the Audio Precision (AP) analyzer does not have a dedicated digital-audio output over USB. Audio data over USB to the device under test (DUT) is achieved via a computer (in our case a Lenovo ThinkPad X1 laptop running Windows 11) running the APx software controlling the AP analyzer. The dedicated Magnetar Windows USB driver for the UDP900 was downloaded from the Magnetar website and installed on our laptop. The driver control panel allows for the selection of 16-bit or 24-bit two-channel data. This, along with the APx software controlling the sample rate, allowed for true 16-bit/44.1kHz, 24/96, and 24/192 audio data to be sent to the UDP900 DAC. The UDP900 has seven user-selectable digital-filter options, but for the digital measurements below, the default filter, labeled Brick Wall, was used.
The UDP900 has both balanced (XLR) and unbalanced (RCA) line-level analog outputs. Typically, we find very little performance difference between both types of outputs (other than an extra 6dB of gain over balanced). In the case of the UDP900, however, noticeably more THD was measured over the balanced outputs. Further, the balanced outputs yielded 7.5dB (as opposed to the typical 6dB) more gain than the unbalanced outputs. At 0dBFS (1.95Vrms over RCA and 4.6Vrms over XLR), the balanced outputs yielded 5dB more THD at 1kHz, and a very significant 20dB more at 20kHz (graphs included in this report) than the balanced ouptuts. For this reason, unless otherwise stated, the unbalanced (RCA) analog outputs were used. The UDP900 also offers a ¼ ″ TRS headphone output, which was also evaluated.
The analyzer’s input bandwidth filter was set to 10Hz–22.4kHz for all measurements, except for frequency response (DC to 1 MHz), FFTs (10Hz to 90kHz), and THD vs frequency (10Hz to 90kHz). The latter to capture the second and third harmonics of the 20kHz output signal.
Published specifications vs. our primary measurements
The table below summarizes the measurements published by Magnetar for the UDP900 compared directly against our own. The published specifications are sourced from Magnetar’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, 1.95Vrms output (RCA) 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.
Parameter | Manufacturer | SoundStage! Lab |
THD+N (1kHz 0dBFS, 24/96) | <0.005% | <0.006% |
Frequency response (24/96) | 20Hz-20kHz (±0.3dB) | -0.2dB at 20kHz |
SNR (A-weighted, 24/96, RCA) | >120dB | 122dB |
SNR (A-weighted, 24/96, XLR) | >130dB | 126dB |
Dynamic range (A-weighted, 24/96, RCA) | >120dB | 122dB |
Dynamic range (A-weighted, 24/96, XLR) | >130dB | 126dB |
Maximum output level (unbalanced) | 2Vrms | 1.95Vrms |
Maximum output level (balanced) | 4.2Vrms | 4.6Vrms |
Channel separation (1kHz 0dBFS, RCA) | >110dB | 142dB |
Channel separation (1kHz 0dBFS, XLR) | >140dB | 150dB |
Our primary measurements revealed the following using the USB input and the unbalanced line-level outputs (unless specified, assume a 1kHz sinewave at 0dBFS, 100k ohms loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Crosstalk, one channel driven (10kHz, 16/44.1) | -121dB | -118dB |
Crosstalk, one channel driven (10kHz, 24/96) | -148dB | -123dB |
DC offset | <-14mV | <-13mV |
Dynamic range (A-weighted, 16/44.1) | 101.7dB | 101.7dB |
Dynamic range (20Hz-20kHz, 16/44.1) | 99.0dB | 99.0dB |
Dynamic range (A-weighted, 24/96) | 122.5dB | 122.4dB |
Dynamic range (20Hz-20kHz, 24/96) | 119.8dB | 118.9dB |
IMD ratio (CCIF, 18kHz and 19kHz stimulus tones, 1:1, 16/44.1) | <-81dB | <-81dB |
IMD ratio (CCIF, 18kHz and 19kHz stimulus tones, 1:1, 24/96) | <-81dB | <-81dB |
IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1, 16/44.1) | <-70dB | <-70dB |
IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1, 24/96) | <-70dB | <-70dB |
Maximum output voltage (RCA) | 1.95Vrms | 1.94Vrms |
Maximum output voltage (XLR) | 4.60Vrms | 4.57Vrms |
Output impedance (RCA) | 51.8 ohms | 51.8 ohms |
Output impedance (XLR) | 280 ohms | 280 ohms |
Noise level (with signal, A-weighted, 16/44.1) | <28uVrms | <22uVrms |
Noise level (with signal, 20Hz-20kHz, 16/44.1) | <32uVrms | <32uVrms |
Noise level (with signal, A-weighted, 24/96) | <22uVrms | <22uVrms |
Noise level (with signal, 20Hz-20kHz, 24/96) | <23uVrms | <23uVrms |
Noise level (no signal, A-weighted, 24 bits)* | 1.38uVrms | 1.38uVrms |
Noise level (no signal, 20Hz-20kHz, 24 bits)* | 1.9uVrms | 1.9uVrms |
THD ratio (unweighted, 16/44.1) | <0.0059% | <0.0058% |
THD+N ratio (A-weighted, 16/44.1) | <0.0069% | <0.0069% |
THD+N ratio (unweighted, 16/44.1) | <0.0061% | <0.0059% |
THD ratio (unweighted, 24/96) | <0.0059% | <0.0058% |
THD+N ratio (A-weighted, 24/96) | <0.0069% | <0.0069% |
THD+N ratio (unweighted, 24/96) | <0.0061% | <0.0059% |
Our primary measurements revealed the following using the USB input and the headphone output (unless specified, assume a 1kHz sinewave at 0dBFS, 300 ohms loading, 10Hz to 22.4kHz bandwidth):
Parameter | Left channel | Right channel |
Maximum Vrms/0dBFS (100k ohm load) | 4.47Vrms | 4.45Vrms |
Maximum output power into 600 ohms (max volume) | 29.3mW | 29.0mW |
Maximum output power into 300 ohms (max volume) | 51.9mW | 51.4mW |
Maximum output power into 32 ohms (max volume) | 124.6mW | 123.0mW |
Output impedance | 39.9 ohms | 39.9 ohms |
Noise level (with signal, A-weighted, 16/44.1) | <31uVrms | <31uVrms |
Noise level (with signal, 20Hz-20kHz, 16/44.1) | <35uVrms | <35uVrms |
Noise level (with signal, A-weighted, 24/96) | <24uVrms | <24uVrms |
Noise level (with signal, 20Hz-20kHz, 24/96) | <26uVrms | <26uVrms |
Noise level (no signal, A-weighted, 24 bits) | <4.0uVrms | <4.1uVrms |
Noise level (no signal, 20Hz-20kHz, 24 bits) | <7.8uVrms | <8.1uVrms |
Dynamic range (A-weighted, 16/44.1, max output) | 101.6dB | 101.6dB |
Dynamic range (A-weighted, 24/96, max output) | 120.1dB | 120.1dB |
THD ratio (unweighted, 16/44.1) | <0.0041% | <0.0045% |
THD+N ratio (A-weighted, 16/44.1) | <0.0048% | <0.0053% |
THD+N ratio (unweighted, 16/44.1) | <0.0043% | <0.0046% |
THD ratio (unweighted, 24/96) | <0.0040% | <0.0043% |
THD+N ratio (A-weighted, 24/96) | <0.0047% | <0.0051% |
THD+N ratio (unweighted, 24/96) | <0.0041% | <0.0044% |
Frequency response (16/44.1, 24/96, 24/192 with Brick Wall filter)
The plot above shows the UDP900’s frequency-response (relative to 1kHz) as a function of sample rate. The blue/red traces are for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz, the purple/green traces are for a 24/96 dithered digital input signal from 5Hz to 48kHz, and finally orange/pink represents 24/192 from 5Hz to 96kHz. The behavior at low frequencies is the same for all digital sample rates—perfectly flat down to 5Hz. The behavior at high frequencies for all three digital sample rates is as expected, offering sharp filtering around 22k, 48k, and 96kHz (half the respective sample rate). The -3dB point for each sample rate is roughly 20.3, 44 and 81kHz respectively. The ripples (about +/- 0.2dB) in the frequency responses at higher frequencies are real—confirmed with steady-state measurements. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue, purple or orange trace) is performing identically to the right channel (red, green or pink trace), and so they perfectly overlap, indicating that the two channels are ideally matched.
Digital linearity (16/44.1 and 24/96 data)
The graph above shows the results of a linearity test for the digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the line-level unbalanced outputs of the UDP900. The digital input was swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output was analyzed by the APx555. The ideal response is a straight flat line at 0dB (i.e., the amplitude of the digital input perfectly matches the amplitude of the measured analog output). The 24/96 input data is perfect down to -120dBFS, while the 16/44.1 input data began to over-shoot significantly below -90dBFS. The 24/96 data yielded such superb results that we extended the sweep down. . .
Digital linearity (16/44.1 and 24/96 data)
. . . to -140dBFS. Above we see that even at -140dBFS, the UDP900 is only overshooting by 1dB. This is an exemplary linearity test result for the 24/96 data, but somewhat poor for 16/44.1 data (a good result would be flat down to -100dBFS).
Impulse response
The graph above shows the impulse responses for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s) for one sample period then back to digital silence, fed to the digital input, measured at the unbalanced analog outputs, for the left channel only. We can see that UDP900 DAC reconstruction filter exhibits symmetrical pre/post ringing as seen in a typical sinc function.
J-Test (USB input)
The plot above shows the results of the J-Test test for the USB input measured at the unbalanced line-level output of the UDP900. J-Test was developed by Julian Dunn the 1990s. It is a test signal—specifically, a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (i.e., 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sinewave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (e.g., 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA (fundamental at 250Hz) down to -170dBrA for the odd harmonics. The test file can also be used in conjunction with artificially injected sinewave jitter by the Audio Precision, to also show how well the DAC rejects jitter.
The USB digital input shows an average J-Test result, with a few peaks at the -125dBrA level and below, clearly visible both near the primary 12kHz signal peak, and below 1kHz. This is an indication that the UDP900 may be sensitive to jitter.
Wideband FFT spectrum of white noise and 19.1kHz sinewave tone (Brick Wall filter)
The plot above shows a fast Fourier transform (FFT) of the UDP900’s line-level output with white noise at -4 dBFS (blue/red) and a 19.1 kHz sinewave at 0dBFS fed to the coaxial digital input, sampled at 16/44.1 (purple/green). There is a steep roll-off above 20kHz in the white-noise spectrum, characteristic of a brickwall-type filter. There are no imaged aliasing artifacts in the audioband above the -130dBrA noise floor. The primary aliasing signal at 25kHz is at -100dBrA.
THD ratio (unweighted) vs. frequency vs. load (24/96)
The chart above shows THD ratios at the line-level output into 100k ohms (blue/red) and 600 ohms (purple/green) as a function of frequency for a 24/96 dithered 1kHz signal at the USB input. Also shown are THD ratios for the balanced output (pink/orange) into a 200k ohm load. The 100k and 600 ohms data are identical throughout the audioband, which is in indication that UDP900’s outputs are robust and can handle loads below 1k ohms with no difficultly. THD ratios from the unbalanced outputs into 100k ohms ranged from 0.005% from 20Hz to 800Hz, then up to 0.01% at 3kHz, then down to 0.006%at 20kHz. The balanced outputs yielded THD ratios from 0.005% from 20Hz to 100Hz, then a steady rise to 0.06% at 20kHz.
THD ratio (unweighted) vs. frequency vs. sample rate (16/44.1 and 24/96)
The chart above shows THD ratios at the line-level output into 100k ohms as a function of frequency for a 16/44.1 (blue/red) and a 24/96 (purple/green) dithered 1kHz signal at the optical input. THD ratios were identical and ranged from 0.005% from 20Hz to 800Hz, then up to 0.01% at 3kHz, then down to 0.006% at 20kHz.
THD ratio (unweighted) vs. output (16/44.1 and 24/96)
The chart above shows THD ratios measured at the line-level unbalanced output as a function of output voltage for the USB input into 100k ohms from -90dBFS to 0dBFS at 16/44.1 (blue/red) and 24/96 (purple/green). Also shown are THD ratios for the balanced output (pink/orange) into a 200k ohm load. For the unbalanced output, the 24/96 data outperformed the 16/44.1 data at low output voltages by roughly 20-30dB, with a THD range from 0.1% at 200uVrms to 0.0002% at 0.25Vrms, then up to 0.005% at the maximum output voltage of 1.95Vrms. The 16/44.1 data ranged from 10% down to 0.002% at 0.5 to 1Vrms, then up to 0.005% at 1.95Vrms. The balanced output (at 24/96) yielded slightly higher THD ratios (2-3dB) than the unbalanced output up to about 0.1Vrms. From 0.1 to 1Vrms, THD ratios over the balanced output were as much as 15dB higher than the unbalanced output.
THD+N ratio (unweighted) vs. output (16/44.1 and 24/96)
The chart above shows THD+N ratios measured at the line-level unbalanced output as a function of output voltage for the USB input into 100k ohms from -90dBFS to 0dBFS at 16/44.1 (blue/red) and 24/96 (purple/green). Also shown are THD+N ratios for the balanced output (pink/orange) into a 200k ohm load. For the unbalanced output, the 24/96 data outperformed the 16/44.1 data at low output voltages by roughly 15dB, with a THD+N range from 1% at 200uVrms to 0.0015% at 0.5Vrms, then up to 0.006% at the maximum output voltage of 1.95Vrms. The 16/44.1 data ranged from 10% down to 0.003% at 1Vrms, then up to 0.006% at 1.95Vrms. The balanced output (at 24/96) yielded slightly higher THD+N ratios (2-3dB) than the unbalanced output up to about 0.2Vrms. From 0.2 to 1Vrms, THD+N ratios over the balanced output were as much as 5dB higher than the unbalanced output.
FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the line-level unbalanced output into 100k ohm for the USB digital input, sampled at 16/44.1. The third (3kHz) signal harmonic dominates at -85dBrA, or 0.006%. There are also a multitude of low levels peaks from 100Hz to 20kHz just below the -120dBrA, or 0.001%, level.
FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the unbalanced output into 100k ohm for the USB digital input, sampled at 24/96. We see the same signal harmonic dominate at 3kHz at -85dBrA, or 0.006%, as is seen in the 16/44.1 FFT above. We find a power-supply-related noise peak at 120Hz at -130dBrA, or 0.00003%.
FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS, balanced output)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the balanced output into 200k ohm for the USB digital input, sampled at 24/96. Compared to the FFT above with the unbalanced output, here we see clearly visible higher odd-ordered signal harmonics (5/7/9/11kHz, etc.) from -95dBRa, or 0.002%, to -130dBrA, or 0.00003%, at 20kHz.
FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the line-level output into 100k ohms for the USB digital input, sampled at 16/44.1 at -90dBFS. We see the signal peak at the correct amplitude, with significant odd-ordered signal harmonics at -100dBrA, or 0.001% and below.
FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)
Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the line-level output into 100k ohms for the USB digital input, sampled at 24/96 at -90dBFS. We see the signal peak at the correct amplitude, no signal harmonics, and even-ordered power-supply-related noise (120/240/360Hz) dominated by the 120Hz peak at -125dBrA, or 0.00006%.
Intermodulation distortion vs. generator level (SMPTE, 60Hz:4kHz, 4:1, 16/44.1, 24/96)
The chart above shows intermodulation distortion (IMD) ratios measured at the line-level unbalanced output for 16/44.1 (blue/red) input data and 24/96 input data (purple/green), from -60dBFS to 0dBFS. Here, the SMPTE IMD method was used, where the primary frequency (F1 = 60Hz) and the secondary frequency (F2 = 7kHz) are mixed at a ratio of 4:1. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 16/44.1 data yields IMD ratios from 1% down to 0.005% at -10dBFS, then up to 0.03% at 0dBFS. The 24/96 data yields IMD ratios from 0.1% down to 0.002% at -15dBFS, then up to 0.03% at 0dBFS.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, 16/44.1)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the unbalanced line-level output into 100k ohms for the USB input at 16/44.1. The input dBFS values are set at -6.02dBFS so that, if summed for a mean frequency of 18.5kHz, would yield 1.95Vrms (0dBrA) at the output. We find it difficult to identify the second-order modulation product (i.e., the difference signal of 1kHz) amongst the array of noise peaks just below the -120dBrA, or 0.0001%, level, while the third-order modulation products, at 17kHz and 20kHz, are at -95dBrA, or 0.002%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, 24/96)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the line-level output into 100k ohms for the USB input at 24/96. The input dBFS values are set at -6.02dBFS so that, if summed for a mean frequency of 18.5kHz, would yield 1.95Vrms (0dBrA) at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz), is at -135dBrA (right channel only), or 0.00002%, and the third-order modulation products, at 17kHz and 20kHz, are at -95dBrA, or 0.002%.
Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, 24/96, balanced output)
Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the balanced line-level output into 200k ohms for the USB input at 24/96. The input dBFS values are set at -6.02dBFS so that, if summed for a mean frequency of 18.5kHz, would yield 4.6Vrms (0dBrA) at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz), is at -130dBrA, or 0.00003%, and the third-order modulation products, at 17kHz and 20kHz, are at -70dBrA, or 0.03%. Again, the result for the balanced output is much worse than for the unbalanced output.
Intermodulation distortion FFT (24/96 input, APx 32 tone)
Shown above is the FFT of the unbalanced outputs of the UDP900 with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 1.95Vrms. The intermodulation products—i.e., the “grass” between the test tones—are distortion products and are around the extremely low -120dBrA, or 0.0001%, level.
Diego Estan
Electronics Measurement Specialist
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