Full detailed sound at 30 - 40 - 50 dB

There is always more to it...

@atmasphere 

Hi Ralph. I have a follow up question if you don't mind, as I mentioned I would be re-reading/re-digesting the rather informative information you've already provided.

Regarding the "weighting' where distortion is more problematic depending on which harmonic the distortion occurs, I note that manufacturers - including your own product specifications - provide "total harmonic distortion" and in some cases "intermodulation distortion". Other than subjective listening, how might a customer objectively derive from specifications alone at which harmonics the distortion is occurring? I guess what I'm asking is, is there a way to understand the individual numbers that comprise "total" harmonic distortion? Thanks.

Other than subjective listening, how might a customer objectively derive from specifications alone at which harmonics the distortion is occurring?

That is a good question. You can get some of that from the spectral analysis. this can be tricky- I've seen some of this done on our amps, but the methodology is was incorrect (one speaker terminal got accidentally grounded by the test equipment) so the readings were off. If the measurement technique doesn't introduce problems, this can be one way of sorting things out. 

But if the total is low, the  components must be even lower (or theoretically at most equal).

But if the total is low, the components must be even lower (or theoretically at most equal).

Right, but atmasphere is stating that "a 7th harmonic at 0.005% is a much bigger sin in terms of coloration than a 2nd harmonic at 1%". So even a very low THD still begs the question, "at what harmonic"?

+1 for good tone controls. :)