Class D

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.

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!!