Class D Technology

I have used the Bel Canto Ref600 mono amps for almost 5 years now, currently driving a pair of ATC SCM 19v2 loudspeakers. 99.9% of the time I don’t detect any issues with their performance. Perhaps that 0.1% anomaly could be attributed to their Class D design, but I can’t say with absolute certainty. What I can say is I agree with what some others have said concerning the synergy between the amps and loudspeakers (a relatively flat impedance curve is optimal), and power source and power cables also come into play. I am pretty discerning and sensitive to the quantity of the sound of my system, and I have tried other amps, but the fact that I continue to stick with the Bel Canto Ref600 mono amps for almost 5 years now speaks for itself. Their sound quality was only reinforced after I purchased their new E1X controller/DAC. So I guess you could say I am biased, but as the old saying goes, “the proof is in the pudding”, and I am really enjoying my system.

Happy listening, and remember to enjoy the music!

if it weren't for efficiency & power, would there be any reason to own a Class D amp?

Class D amps rock the category of watts per dollar, which makes them a good choice for powered subwoofers where the goal is control and damping of large drivers while imaging and spatial information doesn't matter.

Do they beat Class A in any other categories that count for sound quality?

Power and control, both of which are harder to achieve economically with Class A.  Otherwise, Class D does not beat Class A in my experience comparing Class A Lamm M1.2s and Clayton M300s with Class D Ncore NC1200 via Acoustic Imagery.  I owned all of those amps and compared them directly in my system over an extended period.  The Class A amplifiers were way better at portraying music naturally and believably, which seemed to relate to the spatial representation of the individual sounds and instruments.  The NC1200 amps also did not beat better Class AB amps, IME.  Better sound quality seems to be the current goal of Class D designers, with pockets of manufacturers and owners claiming that certain topologies and products are getting closer or achieving the goal but so far, the marketplace has not seemed to fully agree in the long term.

     Hello mitch2,

      From some of your past replies on other threads, I remember learning of your disappointments with the performance of some high quality class D amps you've tried in your system.  From what I've read, however, the class A Lamm and Clayton amps sound and perform about as good or better than just about any other amps, regardless of amp type.  I also believe they're both much more expensive mono-block amps than the Acoustic Imagery and many of the other higher quality class D amps. 
     So, I just wanted to point out that class D amps offer what I believe many would consider very good full range sound quality, typically at a very reasonable price and, therefore, would be considered a better bargain and amp option by those with limited budgets.  
     Yes, the main benefits of current class D amps are still power and control, unsurpassed electrical efficiency, ridiculously low distortion and noise floor levels, extremely small size, weight, operating temperatures and relative price. 
     Sure, their overall full range sound quality may not currently and universally be considered the best in absolute terms.  As class D technology continues its steady upward trend in overall full range sound quality performance in absolute terms, however, I believe it currently represents the best, and certainly the most affordable, pathway to high-end sound quality. 
      In my opinion, it'll also likely just be a matter of time before it's universally considered the premiere amp type, especially considering its near-future DSP technology inclusion and potential.  It should at least be very interesting.

Tim  

Tim
Class D absolutely rocks watts per dollar (except of course for gallium-nitride transistor versions) so if they get the other stuff sorted they will be hard to beat.  My only comparisons were the Acoustic Imagery Atsah which are a Ncore NC1200 implementation that I owned for over a year, and H20 amps that I had here for a very short time.  I was initially impressed with the NC1200 Atsahs because of their dense tonality and hard hitting bass but after a longer period of listening and comparing there seemed to be something just a little off, or missing.  It took me a bit to figure out that my issue was with spatial cues that lead to realism.  The NC1200 amplifiers were not inexpensive when they first came out and even the Atsahs at the lower end of NC1200 were still $10K.    
As to Class A, that doesn't necessarily get everyone to the finish line either, even if you neglect the heat and electrical costs.  So much is related to amplifier-speaker synergy as well as the types of music preferred by the listener.  In my case, the Lamms were not powerful enough to adequately drive my power-hungry Aerial speakers on the rock, pop, and blues music I most often listen to.  The Claytons were much closer at 300wpc and they were just outstanding on tone but still displayed a bit of reticence on particularly dynamic passages.  There are always trade-offs.  My upgraded SMc/McCormack Class AB monos finally gave me enough clean power to properly drive my speakers through the most dynamic music, while also getting me sonically close to the dense tone, staging, and extension provided by the Class A Claytons.  They are not necessarily better amplifiers than the Claytons but for my situation, speakers, and musical/listening preferences they are.  

+1 noble100, I was an enthusiast of class D amplification from the start. I replaced my (medium quality) class AB amp (Cambridge A3i) with one of the first class D amps (Rowland 102) based on the one of the cheapest Icepower modules (200ASC) and was very impressed. Recently I replaced it with class AB Benchmark AHB2 rated class A in Stereophile. It is a better (wonderful) amp overall (cleaner, better extensions etc.), but the difference was small, taking into consideration 3x higher cost (in comparison to Rowland that was well made and expensive). Class D technology is only going to improve in time while everything else is pretty much done. There are still some new designs, like my Benchmark AHB2 amps, that dissipate less and have non-recursive NFB, but class D is the future IMHO.