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.

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.



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.


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.

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.

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.]