On Wed, 19 Sep 2007 22:00:37 -0400, Deek wrote:

Wes Stewart wrote:

SNIPPED

So a bandpass filter for example is a distortion generator?

Absolutely! The output does NOT replicate the input. That is distortion!

Your definition of distortion is limited to harmonic distortion. There are other
forms of distortion that have been used throughout the industry for years.

Don't put words in my mouth. I asked *you* whether *you* thought a
BPF was a distortion generator. Now we know your position. Any
device that doesn't have DC to daylight frequency response and a
perfect, infinite headroom, linear transfer function causes
distortion. Gotcha.


When the output does not faithfully replicate the input, including any gain
factor, it is distortion. So, a bandpass filter absolutely introduces distortion
when it is used to exclude components of a broad band of signals.

Better
tip off all of those BC stations and recording studios that are using
equalizers.

recording studios know exactly what they are doing. they are selectively
distorting the audio to achieve a desired effect. See my other post on this topic.

Uh huh. So recording studio personnel know what they are doing, but
when I said earlier:

"Since the purpose of a communication system (unless you're just
peddling hardware) is to communicate, then one has to look at the
trade-off between distortion and intelligibility. If purposefully
"distorting" the signal by frequency shaping, compression, clipping or
any combination thereof improves the intelligibility at the other end
of the circuit then "distortion" is a good thing, semantics aside."

I didn't know what I'm talking about. Right?


A brief course in Fourier transforms will convince you that a distorted sine
wave signal is still a series of sine waves, the fundamental, the 2nd, 3rd, 4th
harmonic, etc. The existence of those harmonics is by definition DISTORTION.

And of course you believe that you are the only one in this discussion
that understands Fourier transforms.



I see. So a perfect sine wave run through a perfect clipper will
generate a 2nd harmonic?


In the general cse the distortion products for all frequency components have to
be considered in the analysis. The coefficients for any one or more frequency
components can have a zero value.

Why are you slipping into the "general case" when everything else you
have put forth is in absolute terms?


A perfect sine wave running through a perfect clipper will produce a square wave
that is harmonically an infinite series of odd valued frequency components.

Which is different from "a series of sine waves, the fundamental, the
2nd, 3rd, 4th harmonic, etc."


A device that cause an amplitude variation as a function of frequency does not
replicate the input signal. By definition that is distortion [I naver stated
that it is harmonic distortion. Your definition of distortion is incomplete.]

You are "distorting" what I said, I never offered any definitions.