Class D

@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.

Sorry, again, your show how ridiculous your statements are.

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.

This statement is wildly incorrect!


Although digital and class D amps both employ switching, it is important to understand that one is digital and the other analog. However the primary difference between the two is the the order of ones and zeros has significance with digital as does the word length. With class D it does not (there is no word length for starters....) and it is always switching states at its switching frequency. In a class D amp its the width of the on and off states that has significance, as these widths describe the audio signal.

As a result the filters are vastly different. The filter in a digital system is usually operating at a *much* lower frequency than a class D amp. So this isn't just about power!!

This statement is wildly incorrect! So this isn’t just about power!!

It’s more about power, because you can’t see the forest for the trees, with what Mark Levinson tried to do by series up "low order" output filters (so they don’t burn out) and trying to get a steeper roll off as not to introduce phase shift into the audio band in the upper mid/highs, which they achieved, but it had then other problems. https://www.stereophile.com/images/1212ML53fig02.jpg
Instead the simpler fix of of doing what Technics SE-R1 did and just raise the switching frequency to 1.5mhz.

It’s more about power, because you can’t see the forest for the trees, with what Mark Levinson tried to do by series up "low order" output filters (so they don’t burn out) and trying to get a steeper roll off as not to introduce phase shift into the audio band in the upper mid/highs, which they achieved, but it had then other problems

This comment really says you don't understand what's going on here. ML didn't do what you're describing. Its obvious from the internal photos that the circuit employs what is known as an 'H' bridge output (which tends to be common in higher powered class D amps). Its also common to see two chokes as a result- one for each half of the bridge circuit. Without knowing further details of the circuit its unwise to speculate further, but the fact of the amp being an H bridge is easy to see if you know what to look for.


The waveform at the link is a 10KHz squarewave. There is a small amount of overshoot, and what looks like a bit of an oscillation on top of the waveform as it is consistent with each iteration so does not appear to be a measurement error. As square waves go, that's not a bad looking one- most power amps will round the leading edge (if open loop/zero feedback you need 100KHz bandwidth to make that leading edge look right).


So I don't see the 'other problems' to which you referred by including that link. I might add though that more modern class D amps do make a better showing of this sort of thing. When you attack a technology based on older examples, it really doesn't help your argument!