"William Sommerwerck" wrote in message
...
OK. I understand why you might contend that a PWM signal is an
alternative
analogue version of the original (conventionally understood) analogue
signal. However, I still believe that calling a class D amplifier
"analogue", and insisting that it is not in any way 'digital' is likely
to
be confusing to the vast majority of conventionally schooled electronic
service engineers, as opposed to those who have sufficient understanding
and
interest in the math of signal digitization and processing to feel
otherwise.
I've known some pretty bright service technicians. In fact, one of them is
one of the most-intelligent and best-educated people I've ever known. Why
should I patronize them by assuming they can't understand?
As far as my quoting web references goes, most normal people consider
this
resource to be the repository of all human knowledge, and the dog's
********
of reference media. Whilst it is of course not always right on
everything,
where there is collected opinion from many many different and respected
sources, and that opinion is broadly consistent, surely any reasonable
person could not be considered stupid, or without thought of their own,
for
accepting it as a lesson. How else do we learn about any subject other
than
to either research it, or be taught it by someone considerd to be an
expert
? Thus, I make no apology for using the 'net as a research tool, and for
citing links to the data I have found.
I use the Web as a research tool, and often refer to (and correct!)
Wikipedia. But I don't assume that because somethingt is on the Web or in
Wikipedia, it's necessarily true.
'
I still contend that there is no real name for the process employed
in a class D amplifier.
There is. It's (usually) analog pulse-width modulation.
Perhaps we need to coin a new name for it. As it's similar in concept to
a
switch mode power supply, maybe we should call it a 'switch mode
amplifier'.
Nothing wrong with that.
OK. I'm going to take one last stab at this. You are right. But at the same
time, you are wrong also. You are applying an out of date definition to a
grey subject, and trying to make it black and white by using that
definition.
To use the linguistic analogy again. Thirty years ago, the word "gay" meant
happy and carefree. Then it was hijacked by homosexuals to describe
themselves in what they felt was a less contentious way. Now if I want to be
linguistically accurate, the word, thirty years later, still means nothing
other than happy and carefree. But a gazillion homosexuals around the world
would disagree with me very strongly. Are they wrong, and me with my lone
voice, right ? No, neither of us is right or wrong. I am theoretically
right, and they are practically right, because the word has now been
accepted into modern language to mean something other than its 'real'
original definition.
The same is true of the word "digital". Thirty years ago, your narrow
definition of a digital signal being one that has been quantized into
representative numbers, was correct. You could not have applied an analogue
audio signal to a Z80 data line, and have expected it to have been able to
do anything with it. However, now, you could apply a two level PWM audio
signal, which you contend is really still analogue, to a port pin on a
completely digital uP IC, and it would have no problem being able to
manipulate that signal, given the appropriate code to do so. The world of
electronics has moved on since the original definition of digital, and the
lines between analogue and digital signal processing, have become much more
fuzzy in the process, to the point where the original 'narrow' theoretical
definition of digital, no longer hacks it in the real world.
Whether or not you like it, or think it right, the word "digital" now tends
to encompass any means of data transfer between devices or equipments, or
any signal processing technology, which employs just two levels. Any
engineer working in the real world of electronics will tell you this. The
many millions of people who believe this, and publish on the web, are *not*
wrong, just because you believe that they are.
Yamaha for instance, define a PWM audio signal as being digital, and with no
apology, see
http://www.global.yamaha.com/news/2003/20031002.html
Do you honestly consider that the designers at a well respected company such
as they, are wrong ?
Likewise, Sanken and Sanyo describe their PWM class D amplifier ICs as being
"digital". Wrong also ?
And Tripath with their famous TA2020 IC used in many home cinema systems ?
Kenwood ? Sony ? JVC maybe ? All wrong to call their PWM based class D
amplifiers, "digital" ?
If you really believe this, then might I suggest that you try e-mailing a
few of their technical or design departments, and put it to them that they
are wrong, and outline your reasoning, based on your definition of the word,
and then report back what they have to say to you ?
Again, I say that you are not wrong, in theory, but neither are you right in
practice, when referring to today's much-changed world of electronics.
Arfa