Who tried Class D only to return to S/S or Tube

Firstly, let’s get a major misconception out of the way: class d amps are not digital, they are analogue.  And not all class d amps have square wave performance as shown above, though listening to square waves doesn't seem too common...Hard to place any real value in the opinions of those who do not even understand the basics of the technology or misrepresent the performance of high quality, state of the art class d.

Secondly, amps are part of a system. They don’t perform or sound the same in all systems. Some may be great in one system and not so great in another. This is true not only for class d but for class a, a/b, etc. Sweeping generalizations based on limited experience or use are worthless.

Thirdly, the objective performance of many class d amps is better than nearly anything any tube amp is capable of, and in the case of Hypex ncore, better than nearly any ss amp one can buy. Subjective performance can not be argued as it is a matter of individual taste. There are many many people who have dumped their ss or tube amps in favor of class d. Claiming the technology is "not there yet" is a bit behind the times and ignores the fact that not only is it "there", but it is replacing class a and a/b ss and tubes amps in large numbers.

Enjoy whatever works for you. No need to put down what others enjoy.

+1 Kuribo

At the risk of sounding like a broken record - switching amplifiers are simply another major amplifier class to choose from. 

Consider the list of major amplifier designers who currently offer a switching amplifier along with their traditional designs. As well as the list of powered speaker designers that use switching amplifiers. 

Have to agree with "georgelofi" - the "ClassDAudio" (brand) SDS-470C is superb and rivals any "hi-end" amp... after burn in and left on and warmed up.  

Though, I do vacillate a bit between my JC-1's, Atma-Sphere M60's, and the SDS-470C.  Depending on the speakers I'm using... I think I find... that one, or another may sound a "wee bit better" than the others.  

But... think... I may end up settling on the SDS-470C... since... they all sound so similar... and the SDS-470C... is small, low-temperature, and hassle-free.  Not to mention - that at it's price it is a "huge bargain!"

The thing is... there is not a big difference in the sound of any of them - so, I really couldn't recommend any one over the others - except in the context I note above.  And... I tend to think that's likely true of several of the class d amps and hi-end amps - that there are only very subtle differences in the sound of any of them that one person or another will find make one better than another.  But, in reality such subtle differences are not really so significant as to definitively determine that to be true -  "Beauty is (only) in the mind of the beholder."

"Once the technology is there and they put that switching frequency way up higher, then and only then will they be able to filter the s**t out of it away from the audio band and leave a nice clean square wave, and only then will Class D have become of age"

Stereophile picture is about right:  1% of about 50V switched at 400kHz.  I’m not sure why it bothers you - you cannot possibly hear 400kHz.  Speaker will respond to average value.  There is distinctive possibility of tweeter modulating this wave with other frequencies, but this would be true only if tweeter’s membrane could move at 400kHz - not likely.  Also any effective radiation from speaker cable would require about 1/10 wave antenna that is 750m/10=75m.  I wouldn’t worry about that with few meter cables.  There is still possibility of cable to cable capacitive coupling but, because of shielding it would me minuscule amount further filtered by amp’s input filters.  There is some phase shift at 20kHz (about 20%), but it is usually the case of any amplifier bandwidth limited to 60kHz (my Rowland 102). Improvement in Mosfets speed will allows better initial linearity that is right now pretty good to start with.  Class D amplifiers suffer less delay (being one stage only) than multistage class AB amps reducing effects of TIM (resulting in softer sound).  Output impedance is also low by design, even without feedback.

Second generation of class D amps was better but I’m not even sure why.  Bel Canto’s Ref1000 got additional power supply caps and inductors.  That possibly reduced noise on the power cable (Power Factor Correction) but Icepower module used in both generations of this amp has line and load regulated power supply (uncommon in class A or AB amps).  My Rowland 102 is plugged into Power correcting Furman conditioner (big cap and inductor plus filters). Second generation of class D amps served one important task - it allowed some critics to remove foot from their mouth.

If top designers like Jeff Rowland, who is very sensitive to noise issues, don’t see any problems in class D or SMPS (that he uses in class AB amps), then I wouldn’t worry about it either and would judge it only on the merit of sound - it is the only thing that counts.  If it sounds good then it is good.