Harmonics – The missing piece of a complex puzzle

A reviewer recently commented to me with his usual insight, on an amplifier with class-D power supply. The story went like this “I was impressed for the first half hour, the sound was so clean and I thought I was onto something. After half an hour, I don’t know why, but the music just became boring and clinical – it just didn’t sound like real music.”

There are any number of explanations for this syndrome which is not unusual. I would like to suggest that one probable reason has to do with something rarely spoken of – Harmonics – these are so influential on music but also highly complex.

To illustrate by example, my son recently wanted to upgrade his violin. The violin specialist related that the sound produced by a good violin will carry all the way to the back of a large concert hall whereas an inferior violin is absolutely incapable of such a feat.

The explanation given was that the overtones (harmonics) of the better violin interact with the primary notes to propagate them better through air. It’s a bit like sprinting – your legs do all the carrying but try not swinging your arms or swinging them in the opposite direction to normal. Harmonics may well be what arm swinging is to running. This is obviously a simplistic illustration of a highly complex subject but it should give pause for thought.

If  harmonics help sound waves travel in air, it’s not much of a stretch to surmise that they affect electrical waves traveling wires. Normally the sonic differences between wires is explained in terms of skin effect (the tendency for the current to flow down the outside of the wire) but this is doubtful as it only occurs at very high frequencies outside the audio bandwidth (intermodulation effects in this case are of a very low order). Others theorise that because the impedance (resistance) of any wire varies at different frequencies, it handles low frequencies differently to high frequencies. This is certainly true but not the whole story.

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