Eversolo Play Streaming Integrated Amplifier Measurements

Link: reviewed by AJ Wykes on SoundStage! Simplifi on September 1, 2025

General Information

All measurements taken using an Audio Precision APx555 B Series analyzer.

The Eversolo Play was conditioned for 1 hour at 1/8th full rated power (~8W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.

The Play offers two analog inputs (line level and phono configurable MM or MC, both over RCA), two digital S/PDIF inputs (RCA coaxial and TosLink optical), an HDMI input, an ethernet connection for streaming, line-level subwoofer outs (RCA), and a pair of speakerlevel outputs. For the purposes of these measurements, the following inputs were evaluated: coaxial digital (RCA), analog line-level, and phono MM and MC.

Most measurements were made with a 2Vrms line-level analog input, 0dBFS digital input, and 8.5/1.6mVrms for the MM/MC phono configurations (this yielded 10W into 8 ohms with volume at maximum). The signal-to-noise (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 60W (in this case, the 60W was achieved with the volume at maximum with both 2Vrms and 0dBFS in).

Based on the accuracy and repeatability at various volume levels of the left/right channel matching (see table below), the Play volume control is likely operating in the digital domain. Consequently, all analog signals are digitized at the Play’s inputs so the unit may apply volume and bass management. The volume control offers a total range from -79dB to +20.9dB (speaker-level outputs) in 0.5dB increments, from -99.5dB to 0dB.

Because the Play is a digital amplifier technology that exhibits considerable noise above 20kHz (see FFTs below), our typical input bandwidth filter setting of 10Hz-90kHz was necessarily changed to 10Hz-22.4kHz for all measurements, except for frequency response and for FFTs. In addition, THD versus frequency sweeps were limited to 6kHz to adequately capture the second and third signal harmonics with the restricted bandwidth setting.

Volume-control accuracy (measured at speaker outputs): left-right channel tracking

Published specifications vs. our primary measurements

The table below summarizes the measurements published by Eversolo for the Play compared directly against our own. The published specifications are sourced from Eversolo’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 (10Hz to 1MHz), assume, unless otherwise stated, a measurement input bandwidth of 10Hz to 22.4kHz and the worst-case measured result between the left and right channels.

Our primary measurements revealed the following using the analog/digital input (unless specified, assume a 1kHz sinewave at 2Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

* limited by clipping of the analog-to-digital converter (ADC)
** above this continuous power level, protection circuit may engage

For the continuous dynamic power test, the Play was able to sustain 132W (1% THD) into 4 ohms using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (13.2W) for 5 seconds, for 5 continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the Play stayed relatively cool to the touch.

Our primary measurements revealed the following using the analog phono (MM configuration) input (unless specified, assume a 1kHz sinewave at 8.5mVrms, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Our primary measurements revealed the following using the analog phono (MC configuration) input (unless specified, assume a 1kHz sinewave at 1.6mVrms, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

* max achievable at 1% THD

Frequency response (8-ohm loading, line-level input)

In our measured frequency-response (relative to 1kHz) chart above, the Play is nearly flat within the audioband (20Hz to 20kHz). At the extremes, the Play is 0.25dB down at 20Hz and 0.4dB up at 20kHz. The -3dB point is just shy of 60kHz with steep attenuation due to the digitization and anti-aliasing filter applied at the analog input, because internally, the Play only processes digital signals. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.

Phase response (8-ohm loading, line-level input)

Above is the phase-response plot from 20Hz to 20kHz for the analog input. The Play does not invert polarity, but due to the sampling by the ADC and the inherent delays associated with this process, the overall phase shift is significant at 1 million degrees at 20kHz.

Frequency response (8-ohm loading, line-level analog input with bass management on)

Above is the frequency-response plot with bass management applied (80Hz cut-off frequency). The purple/green plots are at the speaker-level outputs and relative to 1kHz, blue is the sub-out relative to 20Hz. The cross-over value is at the correct frequency, and the attenuation slope appears to be 18dB/octave.

Frequency response (8-ohm loading, MM phono input)

The chart above shows the frequency response (relative to 1kHz) for the phono input (MM configuration). What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (i.e., zero deviation would yield a flat line at 0dB). We see a very relatively flat response from 20Hz to 20kHz: 0dB at 20Hz, +0.3dB at 100Hz, +0.5dB at 20kHz.

Frequency response (8-ohm loading, MC phono input)

The chart above shows the frequency response (relative to 1kHz) for the phono input (MC configuration). We see essentially the same frequency response as with the MM configuration. Since the input impedance did not change when measured between MC and MM configurations, it would appear the only difference between the two settings is different gain applied to each.

Frequency response vs. input type (8-ohm loading, left channel only)

The chart above shows the Play’s frequency response as a function of input type. The dark green trace is the same analog input data from the previous graphs. 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 pink/orange is 24/192 from 5Hz to 96kHz. The analog-in frequency response is identical to the 24/192 digital input (but for a restricted low-frequency extension). The behavior at low frequencies is the same across all digital input types: -0.4dB at 5Hz. The behavior at high frequencies for all digital input types is typical: the 16/44.1 plot shows brickwall filtering  just past 20kHz; the 24/96 data plot shows brickwall-type filtering right around 48kHz; and the 24/192 plot shows a gentler slope, with a -3dB point at 60kHz.

Digital linearity (16/44.1 and 24/96 data)

The chart above shows the results of a linearity test for the coaxial digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the speaker-level outputs of the Play. For this test, 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 would be a straight flat line at 0dB. Both digital input types performed similarly, approaching the ideal 0dB relative level at -110 dBFS, then yielding perfect results to 0dBFS. At -120dBFS, the 16/44.1 input data overshot the ideal output signal amplitude by 2-4dB, while the 24/96 data overshot by only 1-2dB.

Impulse response (24/44.1 data)

The graph above shows the impulse response for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s) for one sample period then back to digital silence, measured at the speaker-level outputs of the Play. We can see that the Play utilizes a reconstruction filter with no pre-ringing, but significant post-ringing.

J-Test (coaxial)

The plot above shows the results of the J-Test test for the coaxial digital input measured speaker level outputs of the Play. 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. In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least-significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (e.g., 250Hz, 750Hz, 1250Hz, etc). Note that the alternating peaks are in the test file itself, but at levels of -144dBFS and below.  The test file can also be used in conjunction with artificially injected sinewave jitter by the Audio Precision, to show how well the DAC rejects jitter.

We see several peaks in the audioband at -105dBFS and below. This is a relatively poor J-Test result, and an indication that the Play’s DAC may have poor jitter immunity.

J-Test (optical)

The plot above shows the results of the J-Test test for the optical digital input measured speaker level outputs of the Play. We see essentially the same poor result as with the coaxial input, though this one is slightly worse.

J-Test (coaxial, 10ns jitter)

The plot above shows the results of the J-Test test for the coaxial digital input measured speaker-level outputs of the Play with sinewave jitter injected at 2kHz at the 10ns level. We see the tell-tale peaks at 10/14kHz at the -70dBFS level. Further evidence of the poor jitter immunity. The optical input produced a similar result.

J-Test (coaxial, 100ns jitter)

The plot above shows the results of the J-Test test for the coaxial digital input measured speaker-level outputs of the Play with sinewave jitter injected at 2kHz at the 100ns level. We see the tell-tale peaks at 10/14kHz at the -50dBFS level. Further evidence of the poor jitter immunity. Again, the optical input produced a similar result.

Wideband FFT spectrum of white noise and 19.1kHz sine-wave tone (coaxial input)

The plot above shows a fast Fourier transform (FFT) of the Play’s speaker-level outputs with white noise at -4dBFS (blue/red) and a 19.1 kHz sinewave at 0dBFS fed to the coaxial digital input, sampled at 16/44.1. The sharp roll-off above 20kHz in the white-noise spectrum shows the implementation of a brickwall-type reconstruction filter. There are only small (-125dBFS and below) aliased image peaks in the audioband. The main 25kHz alias peak is highly suppressed at -100dBrA. The second, third, and fourth distortion harmonics (38.2, 57.3, 76.4kHz) of the 19.1kHz tone are between -60dBrA and -70dBrA.

RMS level vs. frequency vs. load impedance (1W, left channel only)

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8 ohms or 2.83Vrms) as a function of frequency, for the analog input swept from 10Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .

. . . is the same but zoomed in to highlight differences. Zoomed in, we can see significant deviations (2dB) at high frequencies from 4 ohms to no load, which is an indication of a very low damping factor, or high output impedance. This is typical of many class-D amplifiers. Below 5kHz, deviations are within 0.3dB. The maximum variation in RMS level when a real speaker was used was, as expected, at high frequencies, with a 0.3dB deviation between 6kHz and 20kHz. Below 2kHz, deviations with a real speaker load are small and within about 0.1dB.

THD ratio (unweighted) vs. frequency vs. output power

The chart above shows THD ratios at the output into 8 ohms as a function of frequency (20Hz to 6kHz) for a sinewave stimulus at the analog input. The blue and red plots are for the left and right chanels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 61W. The power was varied using the volume control. All three THD plots are tightly clustered together, except between 3kHz and 6kHz at 61W. THD ratios ranged from around 0.04% at 20Hz, down to 0.005% from 100Hz to 3kHz, then up to between 0.006% (10W) and 0.04% (61W) at 6kHz.

THD ratio (unweighted) vs. frequency at 10W (phono input, MM and MC)

The chart above shows THD ratios as a function of frequency plots for the phono input (MM configuration blue/red traces, MC purple/green) measured across an 8-ohm load at 10W. The input sweep is EQ’d with an inverted RIAA curve. THD ratios were lower for both the right channel (5-10dB) and for the MM configuration. For MM (left channel), they ranged from roughly 0.1% to 0.01%. For MC (left channel), they ranged from 0.5% to roughly 0.01%.

THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms

The chart above shows THD ratios measured at the output of the Play as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right) and a 4-ohm load (purple/green for left/right), with the volume at maximum. THD ratios for the 8-ohm load ranged from 0.01% at 50mW, down to 0.002% at 0.5W to 3W, then up to 0.005% at the “knee,” at just past 68W. The 1% THD mark was reached at 75W, but is due to the ADC clipping. THD ratios for the 4-ohm load ranged from 0.01% at 50mW, down to 0.002% at 0.5W to 2W, then up to 0.02% at 20W, then 0.01% at  the “knee,” at around 110W. The 1% THD mark was reached at 142W.

THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms

The chart above shows THD+N ratios measured at the output of the Play as a function of output power for the analog line-level-input, for an 8-ohm load (blue/red for left/right) and a 4-ohm load (purple/green for left/right), with the volume set to maximum. THD+N ratios for the 8-ohm load ranged from 0.07% at 50mW, down to 0.005% at the “knee.” THD+N ratios for the 4-ohm load ranged from 0.1% at 50mW, down to 0.01% at  the “knee,” with a bump to 0.02% at 20W.

THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)

The chart above shows THD ratios measured at the output of the Play as a function of load (8/4/2 ohms) for a constant input voltage that yielded 5W at the output into 8 ohms (and roughly 10W into 4 ohms, and 20W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find that THD ratios for all three loads are closely clustered together, other than between 800Hz and 1kHz, where the 2-ohm load yielded 10dB higher results. Otherwise, THD ratios ranged from 0.05% down to 0.005%.

THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)

The chart above shows THD ratios measured at the output of the Play as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). Generally, THD ratios are closely clustered together, with real speaker THD ratios hovering above and below the resistive dummy load data with +/- 5dB. The dummy load ranged from 0.03% at 20Hz, down to 0.005% from 100Hz to 1kHz, then up to 0.01% at 6kHz.

IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)

The chart above shows intermodulation distortion (IMD) ratios measured at the output of the Play as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method was used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). Generally, IMD ratios were higher into the real speaker loads, with the three-way speaker yielding the worst results at between 0.02% and 0.05%, compared to the resistive load at 0.005% across most of the sweep. The 2-way speaker ranged from 0.007% to 0.04%.

IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)

The chart above shows IMD ratios measured at the output of the Play as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method was used, where the primary frequency (F1) is swept from 250Hz down to 40Hz and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). We find very similar IMD ratios into all three loads, a constant 0.02% from 40Hz to 500Hz, then down to 0.004% to 1kHz.

FFT spectrum – 1kHz (line-level input)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s second (2kHz), third (3kHz), fourth (4kHz), and fifth (5kHz) harmonics are evident at -90/-100/-110-/120dBrA respectively, or 0.003% to 0.0001%. Subsequent signal harmonics can also be seen around the -120dBrA level. Below 1kHz, we see small power-supply-related noise peaks at 60Hz and 120Hz, right around -120dBrA, or 0.0001%.

FFT spectrum – 1kHz (MM phono input)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the analog phono input configured for MM. Signal harmonics are slightly higher in level compared to the line-level FFT above (-80 to -110dBrA). Power-supply-related noise peaks can be seen at 60Hz and more predominantly at the odd harmonics (180/300/420/540/660 Hz etc) from -90dBrA, or 0.003%, to -110dBrA, or 0.0003%.

FFT spectrum – 1kHz (MC phono input)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the analog phono input configured for MC. Signal harmonics are difficult to distinguish from the myriad noise peaks reaching roughly -90dBrA, or 0.003%. The signal’s second (2kHz) harmonic can, however, clearly be seen at -70/80dBrA (left/right), or 0.03/0.01%. Power-supply-related noise peaks are again dominated at 60Hz and the odd harmonics, from -70dBrA to -90dBrA, or 0.03% to 0.003%.

FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 16/44.1. We see odd/even signal harmonics at -110dBrA to -120dBrA, or 0.0003% to 0.0001%. Noise peaks to the left of the signal peak are non-existent above the -130dBrA noise floor.

FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 24/96. We see essentially the same signal harmonic profile as with the 16/44.1 FFT above.

FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)

Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and no signal or noise related harmonic peaks.

FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)

Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and two small random noise peaks at a very low -140dBrA, or 0.00001%.

FFT spectrum – 50Hz (line-level input)

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the analog input. The X axis is zoomed in from 40 Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most predominant (non-signal) peaks are the signal second (100Hz) and third (150Hz) harmonics at around -80dBrA and -90dBrA, or 0.01% and 0.003%, with other signal harmonics seen below -110dBrA. The worst-case noise peak is at 60Hz at -110dBrA, or 0.0003%.

FFT spectrum – 50Hz (MM phono input)

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the phono input with the MM configuration. The X axis is zoomed in from 40 Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most predominant (non-signal) peaks are the signal second (100Hz) and third (150Hz) harmonics at around -70/-80dBrA (left/right) and -80dBrA, with other signal harmonics seen at and below -100dBrA. The worst-case noise peak is at 60Hz at -90dBrA, or 0.003%.

FFT spectrum – 50Hz (MC phono input)

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the phono input with the MC configuration. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most predominant (non-signal) peak is the signal second (100Hz) harmonic at around -50/-60dBrA (left/right), or 0.3% and 0.1%, with other signal harmonics seen at and below -80dBrA. The worst-case noise peak is at 60Hz at -70dBrA, or 0.03%.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the analog input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -100dBrA, or 0.001%, while the third-order modulation products, at 17kHz and 20kHz, are around -90dBrA, or 0.003%.

Intermodulation distortion FFT (line-level input, APx 32 tone)

Shown above is the FFT of the speaker-level output of the Play with the APx 32-tone signal applied to the analog input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the “grass” between the test tones—are distortion products from the amplifier and are at and below the low -110dBrA, or 0.0003%, level.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 16/44.1)

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 16/44.1. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -120dBrA, or 0.0001%, while the third-order modulation products, at 17kHz and 20kHz, are around -90dBrA, or 0.003%.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 24/96)

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the coaxial optical input at 24/96. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -120dBrA, or 0.0001%, while the third-order modulation products, at 17kHz and 20kHz, are around -90dBrA, or 0.003%.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MM phono input)

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the phono input configured for MM. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -90dBrA, or 0.003%, while the third-order modulation products, at 17kHz and 20kHz, are at the same level.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MC phono input)

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the phono input configured for MC. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -80dBrA, or 0.01%, while the third-order modulation products, at 17kHz and 20kHz, are at -85dBrA, or 0.006%.

Squarewave response (10kHz)

Above is the 10kHz squarewave response using the analog input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the Play’s slew-rate performance. Rather, it should be seen as a qualitative representation of its limited bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (e.g., 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. Due to Play’s limited bandwidth, we can see overshoot in the corners. In addition, we can see the 450kHz switching oscillator frequency used in the digital amplifier section visibly modulating the waveform.

Squarewave response (1kHz)

Above is the 1kHz squarewave response using the analog input, at roughly 10W into 8 ohms, with a 250kHz restricted bandwidth to remove the modulation from the 450kHz oscillator. Here we see a relatively clean square wave reproduction, with just some over-shoot in the corners.

FFT spectrum of 400kHz switching frequency relative to a 1kHz tone

The Play’s class-D amplifier relies on a switching oscillator to convert the input signal to a pulse-width-modulated (PWM) squarewave (on/off) signal before sending the signal through a low-pass filter to generate an output signal. The Play oscillator switches at a rate of about 450kHz, and this graph plots a wide-bandwidth FFT spectrum of the amplifier’s output at 10W into 8 ohms as it’s fed a 1kHz sinewave. We can see that the 450kHz peak is quite evident, and at -30dBrA. There is also a peak at 900kHz (the second harmonic of the 450kHz peak), at -60dBrA. Those peaks are direct results of the switching oscillators in the Play’s amp modules. The noise around those very-high-frequency signals are in the signal, but all that noise is far above the audioband—and therefore inaudible—and so high in frequency that any loudspeaker the amplifier is driving should filter it all out anyway. 

Damping factor vs. frequency (20Hz to 20kHz)

The final plot above is the damping factor as a function of frequency. Both channels show a relatively constant damping factor from 20Hz to 2kHz, then a steep dip, characteristic of many class-D amps.  At low frequencies, the damping factor is high at around 130/120 (left/right), but at 20kHz the damping factor dips to a very low 10.

Diego Estan
Electronics Measurement Specialist