[sdiy] ot: class d audio amp

[Glen]

At 10:26 AM 10/20/03 , Cornutt, David K wrote:

>Bleagh.  Isn't class D one of the circuits that they use
>for RF amps, that only amplify part of the waveform?
>I don't think I've ever heard of anyone using one as
>an audio amp.

The "D" is for "Digital" in this case. 

I saw a very old article once about building a class D amp with 555 timers
and some support circuitry. I believe it used PWM of a high frequency
square wave, filtered the result, and then sent it to a speaker. It was
supposed to be pretty power-efficient, and suitable for battery power. Of
course, this particular circuit wasn't meant to be Hi-Fi, but I have heard
of other class D audio amps that were supposed to give good quality. 

Come to think of it, a 1-bit DAC is pretty much the same idea, albeit at a
lower power level, if I'm not mistaken. I would certainly consider that a
usable level of audio fidelity.

later,
Glen Berry