It's my understanding that class D power conversion modules typically use high levels of global feedback. The input signal is constantly being compared to the output signal (thousands of times per second) prior to the output signal being amplified. The output signal is only sent to be amplified once it matches the input signal and any necessary adjustments have been made. This high level of global feedback, which designers of more traditional amp topologies typically try to avoid at all costs, is a mainstay of class D amp design. My theory is that this high reliance on high levels of global feedback is responsible for class D amps' astounding neutrality and their performing so close to the ideal of 'a straight wire with gain'. Also, my theory is that this design results in excellent frequency response at all volume levels.
As I've stated I have no technical training on amplifier design or electronics. The above is based on personal reading about class D amplification combined with any small amount of rational thought and common sense I may possess. I may have this entirely wrong, however, and would welcome comments and thoughts on my theory from those with more technical knowledge on class D amps than myself.
while it is true that class-D amps use feedback to make them work & while you are right in stating that without global negative feedback a class-D power would not work, I don't think it is correct to correlate the use of global negative feedback to a class-D power amp's sonic quality.
The way class-D architecture was invented/designed/formulated, global negative feedback is part of its entity. So, just because you read global negative feedback you shouldn't relate it in the same way as you would to GNFB in a class-A, AB power amp. The class-D architecture needs GNFB while class-A, AB architectures have topologies that can do with little or no GNFB.
The class-D power amp is a continuous-time, discrete-voltage pulse width modulated system. The 1st gen of class-D power amps used (& still use) analog/linear power supplies (like the type you see in class-A, AB amps). And, now I'm observing that the next gen of class-D power amps are using switch-mode power supplies (which are themselves class-D power supplies). I think the audio SMPS has finally developed to a point where it is has a low enough noise floor & can handle large currents in a compact size.
Sonic qualities of a class-D power amp have to do with
* power supply design
* noise attenuation at the final output (the amp binding posts) - correct choice of filter
* managing the switching noise in the power output transistors i.e. reducing the switching noise impact on the analog circuits that form the overall class-D power amp
* routing of noisy & quiet signals
just to name a few items.
