Unsound - As I understand it class D doesn't need a lot of negative feedback since duty cycle is much more linear than transistor voltage in class AB output stage*. In addition it has inherent low output impedance since speaker is always connected to zero source impedance (GND, VCC) with very low resistance Mosfets. I would just guess that it is less than class A amps (gain before feedback is few hundred) and much less than most class AB amps (gain in order of few thousands). It is also worth mentioning that conversion of voltage to duty cycle is done in one stage oscillator to drive output Mosfets while traditional amplifier requires multiple output stages (hence delays) to get signal from input to output. Negative feedback causes, as Atmasphere mentioned, late summing with input signal and overshoots (time domain) or enhanced odd harmonics (frequency domain). It is called Transient Intermodulation TIM and was unknown until 70's. Some class AB amps even have saturation of output transistors that causes momentary gaps (charge trapped at the junction)with fast changing input signals (our brain compensates but makes us feel tired) - not even possible with class D since output transistors are in saturation anyway (time is analog quantity and not the voltage). For the same reason class d amp cannot become unstable.
Icepower has multiple feedbacks. One feedback, I believe, is for output voltage while another might be controlling time.
* Class AB has additional problem of different (changing) trans-conductance (gain) crossing from one transistor conducting to both transistors conducting (around zero). It is voltage dependent gain that needs negative feedback.
Icepower has multiple feedbacks. One feedback, I believe, is for output voltage while another might be controlling time.
* Class AB has additional problem of different (changing) trans-conductance (gain) crossing from one transistor conducting to both transistors conducting (around zero). It is voltage dependent gain that needs negative feedback.