Class D Technology

1. They are extremely quiet, having THE HIGHEST S/N Ratio and THE WIDEST DYNAMIC RANGE of any amp type, with almost no audible background noise and highly detailed.  I can turn my volume control to maximum without any source playing, put my ear an inch from the tweeter panel of either speaker, and there is absolutely no sound. Is this possible with a class A amp?

Yes, and with tube amps too.

The reason? Your volume control setting is saying something about your preamp and sources but nothing about the amp. We make tube amps that have to be quiet on speakers that are 107 db... try putting your amps and preamp on a set of speakers like that and see how much noise you have then. Low noise is not a weakness nor advantage of class D amps.

Dynamic range isn't a particular strength or weakness either- it is the same as any good amp.

The real strengths of Class D are low cost, high efficiency (about 85%) and because of the latter, smaller size as large heatsinks are not as important. Class D was first proposed in the late 1940s and can be done with tubes. Its a fairly simple technology which is why its also inexpensive to build. **Those** are the strengths; what an individual designer brings to the table and how well its executed is going to have a big effect on how the amp sounds and performs. There is nothing inherent in the technology otherwise that make it inherently better. The reason its showing up in spades is the semiconductor industry is really wanting to make switching transistors right now instead of linear transistors, so audio manufacturers hare having a much harder time getting linear devices as easily as they did in the past and can read the writing on the wall.

If you want to demystify what class D is all about, I recommend reading this article, which really demonstrates how simple class D really is:
 https://hackaday.io/project/4369-class-d-subwoofer-amplifier-out-of-scrap

Yet you, Mr. Designer, dismiss Class D as nothing more than midfi.......

That's general idea, but simple it is not. None of current class D amp modulators uses triangle waves.  If anything it is more sinewave and closely resembles modulator use in Delta-Sigma converters, that produce similar output.  SACD is also a product of such Delta-Sigma modulator and it is basically class D output signal (PWM).  In addition to modulator alone there are different configuration of output stages, output filters, multiple feedbacks etc.  Let just say that it is so "simple" that it took whole PhD work of Karsten Nielsen (Icepower) at University of Denmark to describe theory behind it - much less actual implementation.  Once you take FPGA approach to class D you will find that it is very, very complex.

 

The real strengths of Class D are low cost, high efficiency (about 85%) and because of the latter, smaller size as large heatsinks are not as important.

Lower cost for manufactures, which seems to result in higher margins instead of reduced retail prices. Manufactures have to of course be careful of cannibalization.    

Yet you, Mr. Designer, dismiss Class D as nothing more than midfi.......

Apparently you've not read this thread or you would not have said that; IOW this statement is false.

Lower cost for manufactures, which seems to result in higher margins instead of reduced retail prices. Manufactures have to of course be careful of cannibalization.

This is true- and is a time-honored technique in the world of audio going back a good 60-70 years. First I can recall is when they went from electro-magnet speakers to permanent magnets. Permanent magnet speakers are cheaper to make but we didn't see the price go down way back then. After that it was the transition from high efficiency loudspeakers to lower efficiency types as transistors came in; lower efficiency speakers are cheaper to make but we didn't see the price go down all that much. Then there was the transition from tubes to solid state. Solid state amps are a lot cheaper to build- no filament circuit and no output transformer but the price really didn't go down.  Then we went from LP to CD and CDs are lot cheaper to build but we didn't see the price go down (instead we saw the price of LPs go up after the record industry sorted out that there was still a demand...). Now we're seeing class D supplant traditional solid state in many ways but for some reason they aren't particularly cheaper even though they are cheaper to make.