@carlsbad2 Tell us more.
@glennewdick
there is no digital (I.e. code) in a class D amp, period. your confusing the differences here.
I’m sorry, but the one who is confused is you. The technique used in class D (which I agree does not stand for ’Digital’) is the same PWM (or other pulse-based modulation) used to convert an analogue signal into a digital stream for CD or other digital medium and back into an analogue format. Neither more, nor less. If there are ’digital sound quality’ issues due to quantization or filtering, they would emerge in this transformation neither more nor less than in an ADC converting an analogue signal.
The fact that potentially the only operation performed on the pulse stream so obtained in a class D amp is amplification, and it is not treating the digital stream in other ways, is neither here nor there: they are 1s and 0s whether you like it or not: the transistor is either saturated or cut-off, and in fact any use in the linear zone is not only not-favoured; it is discouraged and unwanted. The analogue signal is not recoverable unless you use the same techniques to demodulate and filter the pulse stream that are used in a DAC (obviously with much higher currents and voltages, but again that is irrelevant).
I’d suggest you get a degree in EE, then perhaps we can google together from the same basis of understanding.