How much distortion can we hear?

[Guerilla]

Don't always believe what you think.

And if I had written can indicate?

 

[DF96]

Two mistakes commonly made:
1. "THD tells us nothing" - this is foolishness dressed up to look like a higher form of wisdom. It is sometimes used to justify favouring high distortion amplifiers.

The THD metric tells us nothing . .

. . as it has no basis in reality whatsoever, it is not science, but religion.

THD is an attempt to construct a single number from harmonic amplitudes. It turns out to be a weak way to do this, as it takes no account of the relative audibility of distortion of different orders. There are alternatives, such as weighted versions of THD, but none of them has become really popular.

People who think THD is all important are mistaken; people who think THD is irrelevant are even more mistaken.

A fraction of a percent of any form of "distortion" is not noticable to the normal human ear.

Not sure I agree. A fraction of a percent of low order distortion is often not noticed; a similar amount of high order distortion could sound unpleasant.

 

[bimo]

People who think THD is all important are mistaken; people who think THD is irrelevant are even more mistaken.

I agree.
The quality of amplifier is not just about THD.
It is difficult to compare the sound quality of 2 amplifier with different THD.
For fair comparison, all other things, except THD must be same.