when you understand how amps work then it gives you and idea of the differences in the output signal and HOW THEY CONTROL THE DRIVER.in the case of 80 to 100db levels where your not pushing the gear near its limits and use enough processing to eliminate any issues yes it is hard to distinguish. class D switches off or on. a a/b c g h are all of linear design. meaning the have a "rise " and "fall" in a linear fashion. class d is anything but linear. the fundamental structure of the wave form is an actual SQUARE WAVE that needs filtration and inductive load.
if you have recordings in high enough resolution the natural characteristics that make each individual sound unique. no amplifier will sound as realistic as the instrument itself but it can get really **** close. that being said every time you convert a signal from one form to another you get losses. its a scientific fact. D/a to A/D now is pretty **** good but it will not match the pure form of the signal. if the signal is digital in nature creating an analog signal you will have losses. same with analog to digital. thats excatly why sampling rate and bit-rate matter. there is MORE INFORMATION BEING "READ"
will the calls D/t amps sound good properly designed? absolutely will it sound better than analog amps? by nature of the processing to recreate the waveform you are creating a unnatural wave form in which sound is made using essentially DC signals that have a pulse width and very fast rise/falls times and relying on the inductive and capacitive nature of the capacitors and inductor in the circuit.
the only reason the voltmeter reads it as AC is because it goes threw the meter.