I lack the technical knowledge of
@restorer-john ,
@March Audio , and
@pma . But as a layperson reading through this discussion, particularly the disagreements between March Audio and Pavel/pma, I see pretty clearly that pma is able to produce signals and tests that can reveal certain
design characteristics of Class D amps. But - and I think this is part of March Audio's point - I have not yet seen any decisive evidence that these design
characteristics are design
flaws.
So for example, if I use a Class AB amp and I drive it hard enough to put it into Class B mode, it will have switching distortion, yes? So should the possibility of switching distortion on an amp running in Class B mode be more or less of a concern to me than the possibility of a Class D amp exhibiting some phase nonlinearity in frequencies above, say, 15kHz?
My answer is, I don't know. I don't know because I don't know how to compare those two different kinds of nonlinearities (aka deviations from perfect fidelity) - but also because I don't know how likely I am to run into either one. Do I really listen to my music loud enough to trigger my amp into Class B mode, and if so, can I even hear any switching distortion? Conversely, are any of my source components even able to produce the phase issues pma displays? And if so, if those phase nonlinearities occur above 15kHz, can I even hear them? (My 50 year-old ears can still hear up to slightly above 17kHz last I tested them with a frequency generator, but at my age I can only hear above 15kHz if I turn my head so one of my ears is more or less directly facing the speaker's tweeter. So I very much doubt I am hearing much above 15kHz when listening to actual music from my normal listening position.)
I'm not saying we shouldn't pursue and discuss these issues. I'm just saying that all topologies have certain characteristics, and I think those characteristics do not correlate in any simple or obvious way with audible problems or design flaws.