Class D Technology

My good buddy Glen (shibui). A fantastic friend, an all-around great guy, and an ardent and experienced audiophile/music lover with a superb-sounding system. What more could anyone ask?

Phase shift and wrong summing of harmonics argument might look plausible (I claimed it myself) if not for the fact that my speakers already limit bandwidth to 22kHz creating larger phase shifts in comparison to 65kHz amp's bandwidth.  This 65kHz amp's bandwidth is responsible for about 20deg phase delay at 20kHz (that I cannot hear) and about 10deg delay at 10kHz (that I can hear).  One can argue that this phase delay might be beneficial since many speakers have positive phase shift at these frequencies.  I don't have data for my speakers, but I picked one of the speakers reviewed by Stereophile.  As you can see on the phase diagram (dotted line) speaker actually accelerates phase at the highest frequencies.  Phase delay caused by the bandwidth limit of my amp would improve summing of harmonics (Al, am I missing something?).  
http://www.stereophile.com/content/monitor-audio-platinum-pl300-ii-loudspeaker-measurements#Oze7AYHq...

There are many class A or AB amps that have bandwidth much lower than 200kHz (including Krells that have -3dB at about 100kHz) but nobody makes claims about  bad sounding highs.  It is a little of negative placebo effect - if you really believe that class D cannot sound good it will not.  

As for the hefty H2O power supply - it is unregulated and as such requires huge bank of capacitors to keep voltage steady and to filter out 120Hz ripple.  Jeff Rowland uses only very quiet SMPS, line and load regulated that operate at 1MHz switching frequency that is very easy to filter out.  In fact, he uses SMPS in preamps (Capri), where efficiency is not important, to lower the noise.  SMPS got bad rap from crude computer applications.  Either way works but traditional "linear" supply generates a lot of switching noise.  Also low inductance capacitors (like slit foil) are very expensive.  Why only a few companies use SMPS?  Perhaps because it is not easy to design good switcher and also because of market demand.  Many people believe that it has to be very heavy to work right.  Tiny ferrite transformers can carry at high frequencies as much power as huge transformers operating at 60Hz - not to mention wide supply voltage range and DC operation.  SMPS in mapman's amp can deliver 36 amperes for a full second!

BTW has anyone ever noticed a reviewer complain about phase shift when reviewing gear at a show? They can find all kinds of faults but seldom if ever that. Are they not listening right or is it just not there? Gotta wonder.....

It is a little of negative placebo effect - if you really believe that class D cannot sound good it will not.

I suspect some truth there as well. I went in not totally sure but willing to believe anything. I think.

SMPS in mapman's amp can deliver 36 amperes for a full second!

And....loving it!

I had a fellow agoner over to listen to my gear a while back. He is a fan of David Berning ZOTL amps. I heard these at CAF last summer and liked those very much as well. He indicated he really liked my setup running off the C5i which is latest and greatest Icepower and pure digital integrated amp as well with both phono and line level analog inputs. I do not know the bandwidth. Its a non issue in regards to what I hear personally so I haven’t even given it a thought. But I still gotta know so need to look it up. The ZOTL tube amps I heard and the C5i had quite a bit in common in regards to the sound IMHO. More evidence its the overall execution that matters more so than the technical approach of individual quality parts.

Kijanki 11-21-2016
One can argue that this phase delay might be beneficial since many speakers have positive phase shift at these frequencies.  I don't have data for my speakers, but I picked one of the speakers reviewed by Stereophile.  As you can see on the phase diagram (dotted line) speaker actually accelerates phase at the highest frequencies.  Phase delay caused by the bandwidth limit of my amp would improve summing of harmonics (Al, am I missing something?).  

No, I don't think you're missing anything, Kijanki, and that's an interesting point.  As is frequently the case it's possible that non-ideal behavior in one part of a system can to at least a loose approximation offset or compensate for non-ideal behavior in another part of a system, and turn out to be subjectively preferable.  And it is true that dynamic speakers in particular commonly have impedances in the top octave or two that are inductive, meaning phase angles that are positive.  On the other hand, though, there are of course many other factors besides impedance and bandwidth that contribute to a speaker's overall time domain performance.

Best regards,
-- Al