Sorry if this comes off as overly pedantic, but I don't believe this statement is actually correct and I wanted to clear up any misconceptions.
There should be no correlation between the physical position of the volume control knob and distortion except how it affects the signal level that reaches the amplifier circuit input. Perhaps noise, but not distortion.
The way this works is this:
- Let's say you have an amplifier that clips with 2V input, and that it has gain of 20X (26dB). This amp will clip with a source voltage of 100mV driving it (2V/20 = 0.1V).
- Let's also say you find the perfect listening volume is attained with an average of 1mV driving the amplifier. That will be amplified by 20X to 20mV average, allowing another 4X of amplification (12dB of 'headroom') .
EXAMPLE A:
Let's say audio source
A has an average output level of
0.1V (100mV). This source has 100X more output voltage than necessary to clip the amplifier driving the speakers. You will need to put a volume control on the input and turn it down enough to attenuate the input by 100X, or -40dB.
Let's say that puts the volume control at exactly 12 o'clock in its rotation, or 50% (half-way up).
EXAMPLE B:
Now, let's say audio source
B has an average output level of
0.01V (10mV). You will need to attenuate this signal less to take it down to our sweet spot of 1mV average signal to the amplifier circuit's input. The signal will need to be attenuated by 10X (-20dB) from 10mV average down to 1mV average.
Let's say that means the volume control will now be at 3 o'clock in its rotation, or 75% (three-quarters of the way up).
In both cases, Ex. A and Ex. B, we've used the volume control to attenuate the incoming average signal level to 1mV.
It does not matter at what position the volume control is set. What matters is the signal level applied to the input of the amplifier.
If an amplifier distorts with even a tiny signal on it just because you turn its volume control up to 75%, then there is something very wrong with that amplifier.