Competitive class D amp suggestions

I have been Class D fun since a few years ago when i bought my first class D amp. I like the concept, in general, and all the attractive features of this class of amplifiers. I tried 4 different ones, currently i  stayed with one of them that i consider to be the best among all four amps. I do enjoy and like it. At the same time,  my 5 watts SET amplifier (with more than 100 times higher distortion according to the specs) gives more natural and (surprisingly) notably cleaner sound (THD of the class D amp is 0.001). The soundstage  of the class D amp is not so bad but that of the tube one is still better.   

I remain attracted by class D amps though. 

Any fresh suggestions on reasonably priced class D amps (i mean excluding  non-reasonably priced class D amps, e.g., Merrill amplifiers)?

Any comments on non-reasonably priced class D amps are also welcome (so far i was not able to audition many class D amps and am curious if there are some which could really compete with Class A). 


Who here actually heard in their own system the Atmasphere class d amps? I'm in line to hear a pr when my dealer gets his demo set. 

I'd like to ask Ralph two questions about class d in general but I will use his class d to ask the questions:

1.  How do I equate a class d amplifiers power output with its power draw.  So for example, your class d amp is capable of producing 100 watts at full full power, how many watts would it draw?

2.  It seems that most class d amp designers are going for the lowest distortion possible. I think I've read correctly that Nelson Pass said that if 2nd harmonics are dominate, an amplifier will sound very musical for music that is not complex and 3rd harmonics are probably preferable for complex music.  I also believe I've read that your goal was to get distortion as low as possible and to have 3rd harmonics be the dominate of any remaining distortion.  Is there a particular reason for 3rd vs a blend of 2nd and 3rd?

I hope I've represented all of the above correctly..



+1 @snapsc

I just heard Mr. Pass mention 2nd order harmonics in an interview. But your question about whether 3rd order harmonics is pleasing for complex music is interesting.

And, while it may seem intuitive to presume that a system that can do complex material can easily tackle less complex music, maybe there is more to it than that.

And now for a movie reference that hopefully someone besides me, gets…

Bueller, Bueller, Bueller?   LOL.  I mean, Ralph.   

Nelson Pass is correct about the 2nd harmonic, great for simple music, but not for complex music. Here is a quote from the late Roger Modjeski on the topic as well:

"Once again, I remind people that 2nd harmonic is not benign on complex music, i.e. anything more than a solo. What people are missing is that large 2nd harmonic distortion also means there is large IMD and here I'm talking of the good old SMPTE test, 60Hz and 6kHz mixed at 4:1. The nice treble note riding on the 60Hz bass gets crushed in the valley of the 2nd harmonic wave. Doesn't anyone think about this? It's so obvious and easy to hear."

I have read a number of times where Ralph talks about 2nd and 3rd harmonics being pleasing to the ear, and where higher ordered harmonics are not. I have his Class D amplifiers and also his M60 monoblocks, as well as a Music Reference OTL and David Berning Quadrature ZOTL amps. The Atma-Sphere Class D is right there with all of them. In fact I have said to Ralph and a number of people who I have had listen to the Class D amps that they in some ways make the OTLs sound obsolete. There is some really cool things that Ralph is doing in his circuit that other Class D manufacturers are not, and it's evident in the sound.

Don't be concerned if Ralph does not pop in here. He is off on a month long bicycle trip riding along the Continental Divide. So his access to the Internet as well as time to respond on this thread may be limited.

Good for can't just be about music and Gear 🤣.

I can't seem to find it now but I think Ralph said that his goal with the Class D Monos was to get the distortion as low as possible and be sure that any residual distortion was dominated by the 3rd Harmonic....and based on how you describe the sound, I wouldn't be surprised if this is exactly what Tommy Obrien was doing at Cherry Amp...although he never actually said it.

What about the wattage draw question...if a class d amp is 90% efficient, does that mean that it draws 110 wats to produce a 100 watt output?