I am learning too. Thats why we are here. Everyone can help in some way, that way we all get better at our hobby. And, the products get better too.
I found this in an article about audio amp classes.
About.com-Anthony Armstrong. Complete article:
http://stereos.about.com/od/homestereotechnologies/a/amp_op_classes.htm
Class D
These amplifiers are erroneously called "digital" amplifiers by the press and many audio "experts." Here's the skinny on Class D:
While some Class D amps do run in true digital mode, using coherent binary data, most do not.
They are better termed "switching" amplifiers, because here the output devices are rapidly switched on and off at least twice for each cycle.
Depending on their switching frequency, they may be "switched on" or "off" millions of times a second.
Class D operation is theoretically 100% efficient, but in practice, they are closer to 80-90% efficiency.
This efficiency gain is at the cost of high-fidelity.
Think of Class D amps as being similar to a switchable power supply, but with audio signals controlling, or modulating, the switching action. To do this, you use a technology called Pulse Width Modulation (or PWM, a technology found in many CD players).
According to experts, audio signals can be used to modulate a PWM system to create a high power audio amplifier at fairly low voltages using very small components. Class D audio uses a fixed, high frequency signal having pulses that vary in width based on input signal amplitude. So, for example, a deep bass note creates a large pulse in the carrier signal. This can be translated into a musical signal by the on/off nature of the output devices.
