Mapman- I won't speak for Ralph but I think you are missing something important here. We are not talking about an amp that is filtering or transforming anything. The issue here is that, supposedly, we perceive certain kinds of distortion (can't remember if its odd or even harmonics) as more harsh or objectionable than others. So, (to make up an example) 0.10% distortion of those harmonics sounds "worse/louder" than 1% distortion of those to which our "ears" (actually brains, I think) are less sensitive. Remember the numbers are made up and I also believe that even within the odd vs. even harmonic dichotomy, there are certain specific harmonics to which our ears are more sensitive.
I only say "supposedly" because I don't have any independent knowledge of the science nor am I an auditory physiologist or experimental psychologist. However, this explanation is consistent with what I remember from my long ago undergrad days about differential response to various kinds of stimuli. This also jibes with what I have heard w my own ears; that ss amps that measure 1X% THD do not, in many cases, sound as good as tube amps that measure 10X% THD.
If your hypothesis is that minimizing THD is an important design goal for an audio amplifier, then many would say that, based on their listening tests, your hypothesis cannot be experimentally verified. That statement does not deny that minimizing distortion is not an important design goal, just that minimizing THD (which is measured in a very specific way) cannot be shown to be an important design goal.
Another way to think of this is that it may be a case of "if your measurements don't match up your experience, maybe you're measuring the wrong thing." In this case, measuring THD may not be the right thing. I think Ralph would suggest a weighted measurement that assigns the most "weight" to those harmonics to which we are most sensitive. Call it WHD (Weighted harmonic distortion) or what have you. The relative weight assigned to each harmonic would have to be determined experimentally, in order for this concept to be applied in practice. When you think about it, THD is actually a specific type of WHD, in which the weight is "1" for each harmonic.
I'll stop now before I dig myself in too deep.
I only say "supposedly" because I don't have any independent knowledge of the science nor am I an auditory physiologist or experimental psychologist. However, this explanation is consistent with what I remember from my long ago undergrad days about differential response to various kinds of stimuli. This also jibes with what I have heard w my own ears; that ss amps that measure 1X% THD do not, in many cases, sound as good as tube amps that measure 10X% THD.
If your hypothesis is that minimizing THD is an important design goal for an audio amplifier, then many would say that, based on their listening tests, your hypothesis cannot be experimentally verified. That statement does not deny that minimizing distortion is not an important design goal, just that minimizing THD (which is measured in a very specific way) cannot be shown to be an important design goal.
Another way to think of this is that it may be a case of "if your measurements don't match up your experience, maybe you're measuring the wrong thing." In this case, measuring THD may not be the right thing. I think Ralph would suggest a weighted measurement that assigns the most "weight" to those harmonics to which we are most sensitive. Call it WHD (Weighted harmonic distortion) or what have you. The relative weight assigned to each harmonic would have to be determined experimentally, in order for this concept to be applied in practice. When you think about it, THD is actually a specific type of WHD, in which the weight is "1" for each harmonic.
I'll stop now before I dig myself in too deep.