Class D Technology

I agree with George that switching frequency should be increased, since 50-60kHz bandwidth limitation introduces around 20deg phase shift at 20kHz (causing wrong harmonics summing), but I’m not even sure I can hear such nuances. There are many highly praised amps that have similar bandwidth, I’m sure.

Switching frequencies are up around 600-800khz at the moment, except for that Technics above.
The problem is the switching noise output filter has to handle the full power of the amp and can only be low order, otherwise it will burn out. And being low order it has an effect down into the audio band. If the switching frequency is 3-5MHz then it can do it’s job well away from the audio band without having phase, fr, ect limitations effects .

Just look at the ringing artifacts in Stereophiles 1kzH square waves of Class D, they now test with a inline heavy filter to make this (ringing) disappear, that Audio Precission’s filter they use makes the test wave look clean, but it’s a con job as it’s done at very low power so it doesn’t burn out, in real use it would last a microsecond.
I have asked JA to include both unfiltered (normal) and filtered square waves, just so readers can see the real deal.
Read comments at the bottom of the page, no answer from him.
http://www.stereophile.com/content/bel-canto-eone-ref600m-power-amplifier#G7miwIhm5pj5EDlK.97

Cheers George

I don’t buy the "gas guzzler" A/B vs. "green" class D arguments for the latter. Kilowatt hours are cheap and relatively clean until you pile up a WHOLE lot of ’em. With typical audiophile usage patterns, and the fact that we’re a VERY small segment of the population, there’s no significant ecological impact here.

The extreme case would be a 100+ Watts pure Class A amp user, who leaves amps on 24/7, switching to a class D amp. Then yes, you’re going from a $1,000+ yearly power bill to like 100 bucks. But that’s an outlier. With more sane usage patterns -- e.g. a class A/B tube amp that you turn on/off as needed -- the difference is close to negligible. And as far as ecological impact, class D probably makes things worse overall, due to the fact that audiophiles ship ’em over, decide they don’t like the sound, and then ship ’em right off again.

If you want to be eco friendly, and be a little compromised at the moment, then sure get a ClassD.
Or pay the bucks and get "maybe the new Technics SE-R1 Class D".
http://www.technics.com/us/products/r1/se-r1.html#overview
Cheers George

I have two integrateds, an Audio Research VSi55 running KT120s and a Peachtree Grand X-1 (Class D).  Through both pairs of speakers I own, Wilson Benesch Arc and BMC PureVox (both retail for $6500, whether these qualify as low-fi, mid-fi or otherwise is a matter of perspective and budget), I'd choose the Peachtree every day.     It sounds every bit as nice as the Audio Research, but runs cool, keeps the electric bill low, and takes up very little space while putting out huge power.  I guess admittedly there are a few cold days each winter where it's nice to use the Audio Research to both play music and heat the room, but otherwise it collects dust.   So I guess in my case, the future arrived 3 years ago when I bought the Peachtree. 

All that stuff about switching frequencies and flux capacitors and quantum math, I don't know anything about that.   I just press the power button, hit play, and sweet music comes out.  For all I know there's a team of hamsters inside the Peachtree playing little tiny violins.  I leave all that stuff to you engineers...if it sounds good, that's all I need to know. 

George, I looked at the link you provided.  Yes they use filters for the purpose of measurements to eliminate residue of switching frequency that is otherwise completely benign. This small residue (about 1%) has no effect on the sound.  Speaker membrane will react (move) to its average value only.

I don’t buy the "gas guzzler" A/B vs. "green" class D arguments for the latter. Kilowatt hours are cheap and relatively clean until you pile up a WHOLE lot of ’em. With typical audiophile usage patterns, and the fact that we’re a VERY small segment of the population, there’s no significant ecological impact here. 

According to this pouring used car engine oil to kitchen sink is OK (does not have environmental impact) since very few people do it.

And as far as ecological impact, class D probably makes things worse overall, due to the fact that audiophiles ship ’em over, decide they don’t like the sound, and then ship ’em right off again

That's funny.