Class D

@georgehifi - How is that any different from digital audio, where DACs get by (very well I might add) with switching frequencies well below a Mhz? And in DACs, there isn’t a practical way to do global feedback since the input is digital, so it’s much more difficult to eliminate filter effects.

George, -200

Stop posting tired graphs, of an older technology that no longer represents state of the art.  Are you familiar with the saying correlation does not equal causation?   You are using the ignorant premise that because one Class-D amplifier has lots of phase shift that all Class-D must.  THAT YOU REFUSE TO LEARN what it means to include the filter in the feedback loop shows your dogmatic ignorance.

What is really funny is you idolize Soulution, even though the person who designed it is not the person quoted ..... well guess what SUNSHINE, Soulution uses a ton of feedback, just like Atmasphere has said repeatedly. A TON.  They do it by having a large gain bandwidth.  Really this is 2nd year circuit in University for engineers. Oh right, you don't actually have an engineering education. Silly me.

How is that any different from digital audio,

The amount of power the filter has to contend with in Class-D amps compared to a dac, now your showing how ridiculous your statements are.

https://www.stereophile.com/images/1212levin.side.jpg note the size of the 4 x!! output switching frequency filter coils in this $53K ML Class-D they had to use, and that’s a monoblock. They tried to series them all up from what I was told, to get a quicker/shallower roll off, as not to effect the phase down into the audioband like this https://ibb.co/vvwzGV5, but it was a disaster as I believe they reacted with each other at certain frequencies and rang, which was what they were trying to get rid of in the first place "switching frequency noise"

Fig.2 Mark Levinson No.53 Reference, small-signal 10kHz squarewave into 8 ohms (no AP testing low-pass filter).

An amplifier with a switching output stage produces ultrasonic noise. However, with no signal, the No.53 had 7mV of noise with a center frequency of 197kHz present at its speaker terminals, which is significantly lower in level than with a conventional class-D amplifier.

(The Anthem Class-D amplifier for example) https://www.stereophile.com/images/1212AM1fig02.jpg

But it worked in getting rid of the switching noise in the $53k ML class-d by here is the 10khz!!!!! square wave with NO external AP testing filter used, almost perfect https://www.stereophile.com/images/1212ML53fig02.jpg, no embedded switching noise, "unheard of for a class-D", except for Technics SE-R1 with does it by moving everything (switching frequency and low order low pass filter) up much higher to 1.5mhz.

How is that any different from digital audio,

The amount of power the filter has to contend with in Class-D amps compared to a dac, now your showing how ridiculous your statements are.

Seems George does not understand how LC filters work.

note the size of the 4 x!! output switching frequency filter coils in this $53K ML Class-D they had to use, and that’s a monoblock.

Without talking with the designer I cannot be sure, but looks like they may be toroidal air-cores or a very low permeability magnetic material to fix a perceived issue (that quite possibly does not exist). This caused it to be large. Designers do crazy things all the time.  Class-D is a big step up for many amplifier designers used to somewhat cookie cutter designs.  There really is not stopping anyone from using a 2 stage LC filter at a high frequency, well other than there is no sonic value to doing so.


https://www.stereophile.com/images/1212AM1fig02.jpg


That's about 450Khz, which with most speakers will never make it to the driver. Point?

@georgehifi - I usually try hard not to get personal on these forums, but you’re continued spewing of misinformation is getting on my nerves. A lot of people on this forum count on knowledgeable people to explain how things work. But you just spout ridiculous drivel. And you keep doing it despite a number of experts like atmosphere and audio2design explaining in straightforward terms why your wrong. But instead of trying to understand what they are saying, you keep regurgitating the same old arguments which don’t even apply to what is being talked about.

I think you better quit while you’re behind. Who knows how much more ridiculous your counter-arguments will become.