Class D is just Dandy!

Delta Sigma processing = digital. :)

Most Class D amps are not digital. Weird. :)

Delta Sigma is not digital. It is a process used for digital encoding and there is a nuance there; its safer to say that data in a memory system is 'digital' (1s and 0s). It is also a good process for encoding for class D operation and is attractive because it allows for direct playback of a class D amp from a digital source, although unless there is some upsampling the clock speeds of most digital sources are far too slow for good class D operation.

All, not most, class D amps are an analog process. The funny thing is, if you want, you can use digital chips (for the most part, inverters) in the class D process. But it is very much an analog process.

Atmasphere,

If you use a delta-sigma encoding process, you are converting analog to digital, no? This AD conversion makes the amps "digital" a step most Class D amps do not need.

Otherwise, please show an example of a Class D amp which uses Delta-Sigma conversion which is not "digital"

it allows for direct playback of a class D amp from a digital source,

There's your hint Eric from Ralph , think about it.

Cheers George

@erik_squires 

If you use a delta-sigma encoding process, you are converting analog to digital, no?

No- not exactly. You are converting from analog to a pulse train. Very convenient for going digital from there, which is why its used in the digital encoding process. But despite that its still an analog process.

I get that this is hard to understand but when you see how much its affected by layout, the need to squelch oscillations and the like, that's when its obvious that despite the way its used, its actually an analog process. Digital stuff does not oscillate. Analog stuff can.

A lot of people think delta-sigma (also known as Pulse Density Modulation or PDM) is digital though (specifically 1-bit). I invite them to build the circuit; in solving the problems of making it work despite it being the circuit in a known-good diagram, that's when you really get that most circuitry that handles digital signals is actually analog. Put another way, the resulting signals are *treated* as if they are digital. I think some would say I am cutting the hair pretty fine, but that really is the truth of it.

BTW, we've moved beyond proof of concept and our scan speeds are up to 0.5MHz now (target is 3MHz, but we won't be able to do that with our through-hole prototypes due to afore-mentioned layout issues that are prone to oscillation at the higher rates). Its sounding pretty good too.