Hello phillyb,
I've shared, and continue to share, your enthusiasm for high end class D amplification for over 6 years now. Class D, in my experience, not only has the clear advantage over more traditional amp types in size, weight, operating temperature, relative cost and electrical efficiency, it also provides excellent overall sound quality results that are already very competitive with the other amps regardless of type or price. I also agree with you that this amp technology is still in its ascendancy.
My only hesitation in universally and fully recommending class D amplification to everyone, is the concern that not everyone seems to share our enthusiasm in its sound quality performance.
Many individuals have claimed for years that they perceive deficiencies in the sound quality performance of class D amps and some have even developed and promoted their own theories as to why, such as georgehifi's consistent proclamations that the class D carrier signal switching frequency is too low and needs to be north of 1 MHz to avoid sonic artifacts in the audible range.
The main issue has been the reality that I, and apparently many other class D amp lovers/users, have completely failed to notice any of these supposed sq deficiencies in their own varied and preferred class D amps. This has naturally resulted in users doubting the sincerity of the class D amp naysayers' claims of sq deficiencies.
Yes, virtually all agree that there were sq deficiencies in much earlier examples of class D amps but not on the numerous better examples produced within the last decade or so. The truth is that if class D amp users perceive none of these claimed sq deficiencies in their own amp's performance then, by definition, none exist since our perceptions literally are each of our realities.
I still believe it's important to keep an open mind, however, especially in this hobby. So, even though there remains a complete lack of legitimate scientific evidence supporting these supposed claims of deficiencies in the sq performance of class D amps, I still don't think it's wise to dismiss the remote possibility that these sq deficiencies actually do exist and that some individuals may be sincerely perceiving them.
After all, it's well known that there are gaps in scientific knowledge and that there's a high probability that important future discoveries will be made about the dynamic and technical forces involved in class D audio reproduction and perception. Perhaps, it will be discovered that some individuals are just more sensitive to certain yet to be identified and measured characteristic(s) of class D amplification.
Because of the above, I strongly suggest that anyone interested in the high quality sq performance and other benefits provided by a high end class D amp, should audition one prior to purchase to guarantee complete satisfaction.
Enjoy,
Tim