Competitive class D amp suggestions

@niodari The first harmonic is the fundamental frequency of the note itself.  So that's the big spike to the far left.  Thus the other harmonics begin with the second.

The reason why the same note/frequency played on a violin and a clarinet sounds different is--simplistically--because different instruments produce different combinations of harmonics... rather like different models of amplifiers!

@snapsc 

The interesting thing from the March Audio review/test is that although the distortion is very low, the remaining distortion is mostly 2nd and 3rd.  The question  becomes "although it has great bass and an extended top end, is it musical"...or is possible that the distortion possibly too low for optimal musicality?

They sounded pretty darn good and musical when I heard the older 120W/ch version.
But I am more in the camp of “give me a wire with gain”, and not in the “spice to taste” camp.
Did hear some Devore O/98s with a Jadis that  sounded nice in LA (SoCal). I did not bust out the iPhone for an SPL reading, but they sounded loud.
They were musical, but not overly quiet in the “low distortion” way.

Horses for courses I suppose??

And as Ralph says here:

Most of them tend to have unmasked higher ordered harmonics at a low level, and because the ear uses the higher harmonics to sense sound pressure, its keenly sensitive to their presence! Also because the ear assigns a tonality to all forms of distortion, this causes most of said amps to sound harsh and bright even though they might have less higher ordered harmonics than a tube amp! This is how important the masking that the 2nd and 3rd provide can actually be.

The speaker (and amp) had a quietness about them.
(And the speakers having low distortion is likely a very big part of that.)

Historically I have usually found it rare to find quiet speakers. It is always a sign that something magical is happening.
I usually find this when I cannot hold a conversation and bust out an SPL measuring app and find it is playing 90-100 dB(A).
But it does not sound as loud as a system playing at 80 dB(A) in a somewhat perplexing way.

I only have found that happening when the speakers and amp have a low distortion, so I have no reason to suspect anything else than what @atmasphere is saying about “the ear” using the harmonics to determine loudness as being likely true.

Personally I do not likely opt for musicality via high distortion over having low distortion electronics and drivers in a speaker that is also not plagued by resonances. While both can sound good with most music… it just seems easier to get good piano and vocals out of a system that is lower distortion and more free of resonances.

But, then again… I have only heard a limited number of systems, and never heard Atmasphere gear in person. I am intrigued by his electronics… so it is (IMO) a low risk decision.
Similarly with the MA gear, it measures very well… and… I have heard it and it also sounds very nice.

Ralph, thank you for the explanation. One thing I’m still not clear about is why people describe class a and high bias a/b as being warm sounding especially if their overall distortion is on the higher side?

Nord Acoustics NC500 MKII Dual Mono

Amazing Amp, my new favorite. I like it better than my PS Audio M700s and/or BHK 300.

One thing I’m still not clear about is why people describe class a and high bias a/b as being warm sounding especially if their overall distortion is on the higher side?

The distortion can be quite low! The tricky bit is knowing what is meant by 'warm'; to some this is a bit of extra mid bass energy. I see it as 2nd harmonic and of course it can be both. I think you'll find though if you delve deeper that those comments do not apply to all. Nelson Pass is aware of how distortion affects tonality so he is careful in his designs to make sure he's got a bit of 2nd going on to help out in that regard.