Competitive class D amp suggestions

@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.

@clio09 ”Too much out there at a fraction of the cost that is a better value in my opinion.”

Yes you pointed out you are a value shopper and it is not a good value. Some people are going for the the best sound they can get. This is their market. But for them it is completely worth the cost. Hence, fr them it is a good value. Values are personal.

@ghdprentice, maybe I should have stated my point a different way. I know too many people who when doing comparisons think along the lines of, "Well it cost $100,000 so it must be better...". To your point, I do go for value, but I go for the highest quality of sound I can attain as well. In addition to moderately priced components I have some very expensive components in my system. All components in my system were chosen for their value, regardless of their price, and because they contribute to the overall enjoyment of my system.

@noske So far,  for me this is a most relevant forum to discuss this since am not aware of other possibilities and i know nothing about electronics. As i have already mentioned, i was not aware of these things before i had a look on the article which seems to be very useful and well written. 

An average is no good if you wish to have an information about the distortion of the harmonics of a particular degree, unless you adjust the weights respectively,. but then you will have different functions, i.e., using current terminology different  "THD" for different harmonics. If ones wishes to have a single universal measure, we may give a large weight to the gain and relatively small or 0 weight to the second and third degree harmonics. But then we will practically ignore the higher order harmonics, which we know are good for may people (who likes tube stuff)! Or a manufacturer may decide which of the "THD"s specify in their products. 

@snapsc , you may be correct about the design strategies of the Cherry amps, Tommy also liked tubes. I think these are second and/or third order harmonics that made me enjoy so much the Megaschino, and my tube SET amp as well. I suggest that it is precisely this tube-like effect of the higher order harmonics that makes the sound so enjoyable. 

Creating alternative "THD" measures seems to me to be a best simple solution to reflect a more precise picture of what is really happening. In fact, we have here a kind of multiobjective and threshold  optimization problem. Our first objective is to minimize the first order harmonics that is also referred to as the gain if i am not mistaken, and also we aim at somehow maximize (!) the distortion in higher order harmonics. Or we may try to maximize the distortion of 2nd and 3rd degree harmonics where we wish to keep the distortion  of the first degree harmonics (the gain) no larger than a certain claimed threshold (for example, 0.001%). Redefining THD in this way,  the producers of the tube amplifiers will  bravely be able to put real distortions that their equipment have.  I don't know about electronics and the limits of the distortions, i.e., would a very large distortion of the 2nd and 3rd order harmonics be good, and what is an ``ideal'' balance between the second and the third order harmonics? 

At this point, with my humble knowledge, i suggest that all this THD (and perhaps other spec parameters) theory is just a b*****t (created by engineers who do not know much about mathematics). It is a non-relevant and non-informative parameter which does not disclose actual balance between the harmonics of different orders.

Electric engineers succeed to develop exceptionally sounding equipment, but the existing parameter for measuring their ``distortion'' seem to me to be useless. 

Electric engineers succeed to develop exceptionally sounding equipment, but the existing parameter for measuring their ``distortion'' seem to me to be useless. 

Engineers have other measurement tools: distortion vs frequency (rising distortion is an indication brightness and harshness may be present), distortion spectra at one Watt and also at 06dB of full power and distortion spectra measured at different frequencies.

If you know what you are looking for, these measurements can tell you how the amp will sound. I agree THD isn't a good marker.