Arfa, please see my other post. Most class D amplifiers are analog, not
digital..

The web in general, would seem to disagree with you on that one, William
....


http://www.pcmag.com/encyclopedia_te...i=55417,00.asp

http://www.pcmag.com/encyclopedia_te...i=55350,00.asp
http://en.wikipedia.org/wiki/Electronic_amplifier
http://www.answers.com/topic/class-d-amplifier
http://www.maxim-ic.com/glossary/ind...063/Tm/class-D

and many many more examples. The signal in a class D amplifier is only
analogue at its input, and at the speaker terminals after the low pass
filter that removes the HF PWM component. Thus, the whole amplifier is
fundamentally digital in the way that it amplifies the signal applied to
it.

The Web is wrong. Most switching amps are analog. That is, everything varies
continuously, rather than in quantized steps.

By the way, Arfa, you're doing something intellectually invalid -- you're
"appealing to authority", rather than thinking for yourself, or explaining
what's going on.

For those who would like to read about the correct explanation of "analog
versus digital", please refer to the following references. (I can't find my
college textbooks, and I don't really think any of these are very good,
because the best explanation is graphical.) Sampling is an analog process,
that involves multiplying the signal by the sampling function, which
produces a convolution in the frequency domain. NO QUANTIZATION OCCURS. If
those convinced that sampling = digitization, let them tell me what the bit
depth is.

http://en.wikipedia.org/wiki/Nyquist...mpling_theorem

http://graphics.cs.ucdavis.edu/~okre...ingTheory.html

http://www2.egr.uh.edu/~glover/apple.../Sampling.html

Here's a quote from the last reference. Note especially the third and
next-to-last sentences.

"The signals we use in the real world, such as our voices, are called
"analog" signals. To process these signals in computers, we need to convert
the signals to "digital" form. While an analog signal is continuous in both
time and amplitude, a digital signal is discrete in both time and amplitude.
To convert a signal from continuous time to discrete time, a process called
sampling is used. The value of the signal is measured at certain intervals
in time. Each measurement is referred to as a sample. (The analog signal is
also quantized in amplitude, but that process is ignored in this
demonstration. See the Analog to Digital Conversion page for more on that.)"

The following is directed at everyone in this group -- and is not a
rhetorical question -- why is it, that when someone _explains_ to you, in a
fairly clear manner, why what you and millions of other people believe to be
true, but _is not_ -- you don't believe them? Aren't you able to think for
yourselves?

The fact that most people do not understand, and refuse to understand, the
difference between analog and digital is, to me, a little frightening,
because it touches on the willingness of human beings to believe what they
want to believe -- or worse, what "experts" tell them -- rather than the
truth.

Disclaimer: When I was a young'un, I thought that if I believed something,
it was so. In retrospect, this is ludicrous, but most people are like that.
It was many years before I recognized this error of thinking.