This is from an audio engineer

In reply to:

Class D is a like a digital switch, 1 or 0, open or closed, on or off. Everytime a change is made, inertia slows the process down a tad. Class A amps on the other hand (rarely found in mobile audio, but all over pro audio) are always on, which allows a faster response...better slew rate. This is why people do not like Class D amps, however, they do work extremely effiencently, especially in the lower frequencies.

The ultra-sonic mess they referred happens all around us. The accepted human hearing range is 20 Hz - 20kHz...right? Anything above is ultrasonic. And what happens to such frequencies in a speaker...they create heat, and lots of it...not a good thing. Okay, back to the filtering out of ultrasonic frequencies, this is basicallly an anti-aliasing filter. I'm not going to get into the details right now because I've been awake for over 24 hours right now.



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