Ever wonder why harmonic distortion figures include the word total? Surely we don’t benefit from knowing partial harmonic distortion.

Or do we?

Harmonic distortion happens when higher frequencies that are not part of the music are added to the signal when passing through our equipment chain.

If we take a single tone, say 1kHz, then inevitably when we run it through our equipment, some extra harmonics are generated. These harmonics occur at odd and even multiples of the fundamental frequency.

So, 1kHz is the fundamental frequency in this example. Harmonics are then generated at even frequencies (2kHz, 4kHz, etc.) and odd frequencies (3kHz and 5kHz).

If we look at just one of these added harmonics that’s simply called distortion. If we look at all the generated frequencies in total (2kHz, 3kHz, 4kHz, 5kHz, etc.) that’s called THD or Total harmonic distortion.

THD is all the added frequencies together that are not supposed to be there.

Paul McGowan / PS AUDIO

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