The Future of Audio Amplification

the noise problem is dealt with through good layout and compact (surface mount) design.

Really then no one one yet has been able to rid of this, and they are mightier minds than you. Only Technics has so far been able to reduce it greatly, with double the switching frequency speed and then the normal output low order filtering of it.

As you can see in this simulated 1khz square wave shot, the ideal is the "grey" square wave no ringing.
The "red" is the what’s available today and it hasn’t changed, the last photo below is whats representative of today’s class-D’s
The Technics is the "blue" uses the GaN transistors, very fast quickly settling and reduced ringing, much closer to resembling the ideal grey square wave.
https://ibb.co/87Kh2mV

And now bench tests of Stereophile, use a special very low power high order -100db line filter between amps output and test gear input.
(Audio Precision’s auxiliary AUX-0025 passive low-pass filter),
Which eliminates noise between amp’s output and test gear input so reader can’t see it anymore.

1khz square wave with AUX-0025 filter in place:
https://www.stereophile.com/images/1212AM1fig03.jpg

1khz square wave without AUX-0025 filter in place:
https://www.stereophile.com/images/1212AM1fig02.jpg

Cheers George

The esthetic beauty of tubes is appealing to many (and deemed silly to others), and with modern technological improvements accumulated over a century or so of refinement, tube amps are currently good enough to still be considered among the best sounding music reproduction devices out there. I think it's based on the relative simplicity of their designs along with the linearity of tubes relative to other things, and hats off to Class D designers for making efficient and explosively powerful amps that work well and fit into small spaces (like live sound speakers). However, for many of us tubes are simply more fun...I was floored when I first heard the little single ended amp I now use, and felt that everything I knew was sort of wrong. Dynamic range from 12wpc? Yep...matched with efficient speakers of course. Noise? No problemo...Heat? Only 4 tubes there sparky, and they last a long time. I can live with the thousands of SS A/B and D watts I use mixing live shows, and my 10 or 12 tube watts in my hifi rig...as long as tubes are available.

Tubes are way cool and if not for deciding to try the latest and greatest new amp technology (Class D) first I might well have headed down the tube amp path several years back but hasn’t happened and I have little interest these days. Technology does in fact keep advancing and you don’t know what is possible until you try it so older technologies face more challenges these days than before perhaps.
Looks do count though and tube amps still look way the coolest by far.

George , Have you researched Exogal or Lyngdorf ? What's your opinion on these 100% digital amplifiers ÷

The Technics is the "blue" uses the GaN transistors, very fast quickly settling and reduced ringing, much closer to resembling the ideal grey square wave.
https://ibb.co/87Kh2mV

And now bench tests of Stereophile, use a special very low power high order -100db line filter between amps output and test gear input.
(Audio Precision’s auxiliary AUX-0025 passive low-pass filter),
Which eliminates noise between amp’s output and test gear input so reader can’t see it anymore.

1khz square wave with AUX-0025 filter in place:
https://www.stereophile.com/images/1212AM1fig03.jpg

1khz square wave without AUX-0025 filter in place:
https://www.stereophile.com/images/1212AM1fig02.jpg

Hm. Seems to make a difference about what you might know about what you are looking at.

In the first link above, no frequency is specified! Its clearly marketing and nothing else.
In the second set of links, what we are seeing appears to be the residual imposed on the square wave. Nothing unexpected. Since the filter is low power, so is the square wave depicted. These links IOW really don’t show anything other than that at the output of a class D amp, there is a residual sine wave as I mentioned before.

Really then no one one yet has been able to rid of this, and they are mightier minds than you. Only Technics has so far been able to reduce it greatly, with double the switching frequency speed and then the normal output low order filtering of it.

:) That’s funny! The reason the Technics has lower residual is because for a given filter turnover frequency (probably about 80KHz), the higher the switching frequency the lower the residual. No mystery- just faster switching times. IOW, what you referred to in the Stereophile links as the ’noise’ is a red herring- its not at all what you **seem** to think you’re talking about.