Class D Technology

Assuming nothing is there to start with isn't a phase shift of 0 = 0?

Nope! The point is that if you don't have the bandwidth in the amp it will cause phase shift at lower frequencies- down to about 1/10th the cutoff frequency is then its considered negligible (of course, 'negligible' by whom is a different story; obviously some designers don't care about that so much). IOW the ear might hear 20-20KHz but to reproduce that in an amplifier without phase shift you need 2Hz to 200KHz if you really want to do it right (the same rule applies on the bottom end; otherwise the bass loses impact due to phase shift). For this reason Stuart Hegman, who designed the h/k Citation 1 and Citation 2 was a big fan of wide bandwidth. 

I did not know vinyl has frequency bandwidth so high.   Most home hifi always talked of 20-20K frequency response.     Is this in practice or theoretical?   I'd agree theoretically vinyl could do more but practically its news to me.   The best digital (higher res) sounds as good as most vinyl to me these days.   RTR is better but look where that got us practically.

Its not just theoretical.

Its true that most LP systems don't spec past 20KHz but you would be very much mistaken if you think it stops there. Most phono cartridges and phono sections made since the mid 1960s go much higher than that (although it does not show in the specs as at the time there was no thought that it made any difference). Our cutter head is an early Westerex 3D, made about 1959 and it has no worries cutting 30KHz which can then be played back by a 1970s Technics on a 1970s h/k receiver (the Westerex mastering system has a filter that cuts it off at about 42KHz). By contrast RTR does not have this sort of bandwidth; about 25KHz or so is the best you're going to get at 15 i.p.s. IOW LPs have wider bandwidth than tape and its been that way since the inception of reel to reel. 

Every time a new system has come into the scene the previous knowledge of the prior engineering often goes by the wayside for a while until the new technology gets its pants on. This happened with digital; its only been recently that its begun pressing bandwidth past 20KHz and we're seeing the same thing with class D right now.  In time this will all get sorted out as the technology improves to the point that such bandwidths are routine; until then essentially what you will see is the industry collectively placing its head in the sand as if these facts don't exist. But this is not rocket science and we've known that bandwidth is essential going on half a century now. But people have short memories when new technology comes in... Look how long people put up with unruly fuel injection while carburetion was pretty figured out and actually performed better. But fuel injection was 'new' so people put up with it. Now days its sorted and no-one would consider a carburetor. But literally it took 3 decades to get there!

Al, thanks for that.

I was aware of the phase shift concerns and recall looking at measurements and reviews prior to buying to get a feel for what is going on.   Knowing no gear measures perfectly in all regards I decided to give it a try and was glad I did. 

I have to say to whatever extent my amps and gear may be imperfect or not, listening enjoyment is not affected.  I can listen for hours and never grow fatigued or tired.   That's not something I could lay claim to with my system prior to Class D. 

So as we know  in the end it always comes down to what one hears and can enjoy or not.    Measurements help scope out the likely candidates in advance, and their technical strengths and weaknesses but never tell the whole story regarding how things actually sound.

So while nobody including me has argued that more bandwidth done right is always a good thing, I do still think its unfair to dismiss Class D technology and products as a whole these days based solely on that.   The benefits will far outweigh the disadvantages for many  but probably not so much for those who are put off for whatever reason.

Shibui,
Thanks for your real world experience driven insight. I will always place more weight on actual use and listening experiences than the hypothetical/theory argument. Ironic given the contrary opinion of some on this threat that tube and class D amplifiers are superb driving your 1 ohm load Apogee speakers.
Charles

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!