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Links: 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

frequency response phono mm

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

frequency response phono mc

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

phase response phono mm

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

phase response phono mc

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

thd ratio unweighted vs frequency_phono mm mc

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

thd ratio unweighted vs output voltage mm mc

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

thd+n ratio unweighted vs output voltage mm mc

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

thd+n ratio a-weighted vs output voltage mm mc

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

fft spectrum 1khz mm

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

FFT spectrum 1khz phono mc low

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

fft spectrum 50hz phono mm

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

fft spectrum 50hz phono mc low

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

intermodulation distortion FFT 18kHz 19kHz summed stimulus phono mm

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

intermodulation distortion FFT 18kHz 19kHz summed stimulus phono 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

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