Audiophilepure

Rather than testing total harmonic distortion at full scale at 1kHz as many do, I prefer to understand what the amplifier is doing over a broader range of frequencies and at a more reasonable output level. So, I do a frequency sweep from 10Hz to 20kHz at 5 watts RMS into 8Ω instead. For reference, 5 watts will usually produce somewhere between 85-105dB sound pressure level depending on the connected speaker’s efficiency. I personally find 85dB to be quite loud for extended listening sessions. (I usually listen in the 75-80dB range for longer sessions to protect against hearing damage.) At 5-watt levels, we see that total harmonic distortion is dominated by 3rd-order products up to about 2.5kHz where 2nd-order distortion takes over. At 20kHz, distortion is about 0.04% which is very close to the manufacturer’s published <0.03% THD.

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