Propeller Head Plaza

Technical and scientific discussion of amps, cables and other topics.

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Re: transient test - Part II

Posted by john curl on July 31, 2003 at 10:34:18:
IM distortion is powerful, but it is not really better than harmonic distortion, in general. You will notice that a triple-tone IM component is the most sensitive of all, but it is only twice a harmonic in level.
For example you can use sine-square IM for TIM, but you can also use extended bandwidth harmonic distortion to get essentially the same results. You just have to swallow the criticism that the extended bandwidth harmonics are NOT audible. Of course, there is a correlation to actual music signals that have the same time rate of change for a portion of the cycle as really high frequency test tones, but it takes a leap of faith and experience to take it for granted. Also, PIM is a function of non-linearity and open loop bandwidth in a feedback amplifier.
There are other distortion mechanisms that develop separately from IM-harmonic distortion producing sources. These are DA and Hirata based distortion. They are separate issues.