Competitive class D amp suggestions

@snapsc Thankyou for that link, that is tremendous information.

This leads me to wonder about the virtues of Purifi module Class D amps. Tests reveal the near total absence of any audible 2nd and 3rd harmonics.

I guess it depends on the maker using Purifi technology, but I have recently been reading all I can about March Audio.

So "good" is bad. True.. While I haven’t auditioned, I remain cautious.

I am very sad that Ralph’s Class D is designed only for Nth America and Canada (and perhaps a few others) electricity supply, otherwise I’d be placing my order.

AGD? Hmm. If I really have to, kinda thing.

Actually, I don't know how the second and third order harmonics are dealt with in class d amplifiers in general, and in GaN class d  amplifiers, in particular. Any input on the subject would also be appreciated. 

Perhaps because they are there but rather inaudible to mortals.  This review puts a March Audio (Purifi based) amp through the tests.  Some lower order harmonics *do* exist (maybe contrary to what I said previously) but at barely there levels.

I have not seen any GaN tests.  Some may exist, but not for AGD or Atmas that I am aware of.  I can't recall the dude at AGD even mentioning harmonics in his rather infrequent announcements..

Perhaps what we need is an amp with variable second and third harmonic controls, so that we can dial in the exact mix that we prefer.  

This can be done with digital signal processing, or something similar. I think its a good idea - that is I think what Nelson Pass used on test subjects to reach his optimal tweaking of included harmonics.

I don't know how difficult it would be to realistically implement in an analogue amp intended for home use.. Probably would be expensive - just a wild guess.

@niodari THD takes a mere weighted sum of gain, the second and third degree harmonics. More refined parameter would measure the distortion of the gain, second and third order harmonics separately.

Yeah, and SINAD. This is probably not the right forum to discuss issues of specific weightings as it is quite a mathmatically beguiling issue. This, I think, is understood.

I look at a threshold metrics. Should they be met, then a visual of what else is presented is worthy of further examination - this is perhaps three or four other parameters, on a good day.

And this is becoming reasonably well understood by many inquisitive folk, with thanks to a small number (one?) of .educational resources that did not exist until recent years,  Plus valued contributions by exceptionally knowledgeable people.

In unrelated news, Topping has recently released a new version of its D90SE DAC, called the D90LE, and that is unremarkable in the current context.

What may be of interest, perhaps for educational purposes only, is that included in the new firmware is the option to simulate either tube harmonics or transistor harmonics (or neither).  Specifically, just 2nd and 3rd harmonics, fixed for either option.

Scroll over three quarters way down here to "Sound simulation", and there are images of the fundamental and its two prominent harmonics spikes (sadly the images are not very clear).