Anthem P2 Stereo Amplifier Measurements

Link: reviewed by Doug Schneider on SoundStage! Hi-Fi on August 1, 2025

General information

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

The Anthem P2 was conditioned for 1 hour at 1/8th full rated power (~40W 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 P2 is a two-channel amplifier with two sets each of balanced (XLR) and unbalanced (RCA) inputs and two sets of speaker level outputs. An input of 320mVrms was required to achieve the reference 10W into 8 ohms. There is a third input option—XLR -6dB—which is balanced but reduces gain from 29dB to 23dB. Unless otherwise stated, the XLR input was used (29dB of gain); however, 1kHz 10W FFTs are provided in this report for all three input selections.

Our typical input bandwidth filter setting of 10Hz-22.4kHz was used for all measurements except FFTs and THD versus frequency, where a bandwidth of 10Hz-90kHz was used. Frequency-response measurements utilize a DC to 1MHz input bandwidth.

Published specifications vs. our primary measurements

The table below summarizes the measurements published by Anthem for the P2 compared directly against our own. The published specifications are sourced from Anthem’s website, either directly or from the manual available for download, or a combination thereof. Assume, unless otherwise stated, 10W into 8 ohms and a measurement input bandwidth of 10Hz to 22.4kHz:

* 9.6k ohms for each individual differential input

Our primary measurements revealed the following (unless specified, assume a 1kHz sinewave at 320mVrms at the input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

For the continuous dynamic power test, the P2 was able to sustain about 580W into 4 ohms (~3% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (58W) 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 top of the P2 was warm to the touch.

Frequency response (8-ohm loading)

In our frequency-response plot (relative to 1kHz) above, measured across the speaker outputs at 10W into 8 ohms, the P2 exhibits a close-to-flat frequency response across the audioband (0/-0.2dB at 20Hz/20kHz). The P2 is only about -0.1dB down at 5Hz. The -3dB point is at roughly 150kHz. 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)

Above is the phase-response plot from 20Hz to 20kHz for the balanced line level input, measured across the speaker outputs at 10W into 8 ohms. The P2 does not invert polarity and exhibits, at worst, only -10 degrees of phase shift at 20kHz, due to its extended bandwidth.

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

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8ohms or 2.83Vrms) as a function of frequency, for the analog line-level 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. Here we find the maximum deviation between an 4-ohm load and no-load to be just under 0.04dB up to 2kHz. Beyond 2kHz, the deviations are as high as 0.18dB at 20kHz. This is an indication of a very high damping factor or low output impedance. With a real speaker, the deviations from 20Hz to 4kHz were lower at roughly 0.02dB.

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 for a sinewave stimulus at the analog line-level input. The blue and red plots are at 1W output into 8 ohms, purple and green at 10W, and pink and orange at 300W. All THD results below about 1kHz are tightly grouped (within 5dB), hovering around the 0.0005-0.001% level. The 1W and 10W data rise to the 0.005-0.01% level at 20kHz, while the 300W data rise to 0.03% at 20kHz.

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 P2 as a function of output power for the analog line-level input for an 8-ohm load (blue/red) and a 4-ohm load (purple/green). The 8-ohm data were fairly constant at 0.001% from 50mW to the “knee” at 300W, then up to the 1% THD mark at 351W. The 4-ohm data were fairly constant at 0.002% from 50mW to the “knee” at 500W, then up to the 1% THD mark at 573W.

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 P2 as a function of output power for the analog line-level input for an 8-ohm load (blue/red) and a 4-ohm load (purple/green). The 8-ohm data ranged from 0.01% at 50mW, down to a low of 0.001% from 20W to 300W, then up to the “knee.” The 4-ohm data ranged from 0.02% at 50mW, down to a low of 0.002% from 20-500W, then up to the “knee.”

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 P2 as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yielded roughly 100W at the output into 8 ohms (blue), 200W into 4 ohms (purple), and 400W into 2 ohms (pink). The 8-ohm and 4-ohm data track closely (within 2-3dB), ranging from 0.0005% at 20-200Hz, then up to 0.04% at 20kHz. The 2-ohm data yielded 0.001% at 20Hz with a steady climb to 0.04% at 20kHz. This shows that the P2 is perfectly stable into 2 ohms, with low THD ratios even at 400W.

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 P2 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). At very low frequencies, the two-way speaker yielded the highest THD ratios (0.02%). In the 100Hz to 6kHz range, THD ratios into all three loads ranged from 0.0004% at 2kHz (two-way speaker) to 0.001% from 150Hz to 5kHz (three-way speaker) to a steady rise from 0.0006% (100Hz) to 0.002% (6kHz) for the resistive load. The highest THD result at 20kHz was from the three-way speaker at just over 0.01%.

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 P2 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). The IMD results into the resistive load range from 0.001 to 0.002% across the sweep. The results into the two-way speaker range from 0.0006% to 0.004%, while the three-way speaker results range from 0.001% to 0.007%.

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 P2 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). All three plots are within 4dB of one another with a constant 0.003-0.005% across the sweep.

FFT spectrum – 1kHz (XLR 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 balanced analog line-level input. We see that the signal’s second (2kHz), third (3kHz) and fourth (4kHz) signal harmonics dominate at -100dBrA (2kHz) and -110dBrA (3/4kHz), or 0.001% and 0.0003%. Other signal harmonics can be seen at and below the -120dBrA level, or 0.0001%. There are power-supply noise-related harmonics at and below the -120dBrA, or 0.0001%, level throughout most of the audioband.

FFT spectrum – 1kHz (XLR -6dB 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 balanced analog line-level input using the -6dB (23dB of gain versus 29dB) setting. The signal harmonic profile using this setting is worse, although it’s not clear whether this is due to the setting itself or the doubling of the input signal to achieve the same 10W at the output. Higher-order signal harmonics (5kHz and above) reach the -110dBrA, or 0.0003%, level all the way up to 100kHz. This is not seen in the FFT above using the standard XLR input. Power-supply noise-related harmonics are the same as the standard XLR FFT above.

FFT spectrum – 1kHz (RCA 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 unbalanced analog line-level input. The FFT is very similar to the FFT using the RCA input. The main differences between RCA and XLR inputs are: a -110dBrA versus -120dBrA noise peak at 60Hz; smaller higher-order power-supply related peaks at -140dBrA instead of -120dBrA; a slightly lower noise floor (-150dBrA instead of -145dBrA), likely overall due to fewer components used and therefore less uncorrelated noise; a more prominent cluster of noise peaks centered around 16-17kHz reaching -120dBrA instead of -130dBrA.

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 balanced analog line-level 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 most dominant (non-signal) peak is the signal’s second (100Hz) signal harmonic at -105dBrA, or 0.0006%. Subsequent signal harmonics are at the -120dBrA, or 0.0001% level, while power-supply-related noise peaks are at and below the same level.

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 balanced analog line-level input. The input RMS values were 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 products (i.e., the difference signal of 1kHz) are at -110dBrA, or 0.0003%, level, while the third-order modulation products, at 17kHz and 20kHz, are a little higher at just under-100dBrA, or 0.001%.

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

Shown above is the FFT of the speaker-level output of the P2 with the APx 32-tone signal applied to the 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 just below -120dBrA, or 0.0001%.

Square-wave response (10kHz)

Above is the 10kHz squarewave response using the balanced analog line-level 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 P2’s slew-rate performance. Rather, it should be seen as a qualitative representation of the P2’s relatively wide 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. In this case, we see a very clean result, with no ringing in the corners and only very mild softening.

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

The final graph above is the damping factor as a function of frequency. We find very high damping factor values, around 500 from 20Hz to 2kHz. Above 2kHz, there is a dip in damping factor, reaching 100 at 20kHz. This is a very strong damping factor result.

Diego Estan
Electronics Measurement Specialist