Subject: [linux-audio-dev] Re: Cheby amp code
From: Steve Harris (S.W.Harris_AT_ecs.soton.ac.uk)
Date: Sun Nov 03 2002 - 18:34:58 EET
On Sun, Nov 03, 2002 at 05:08:33 +0100, Tim Goetze wrote:
> the peak value of the chebyshev-shaped output will be the sum of all
> coefficients calculated in this manner. the further the incoming sine
> is scaled down (from [-1,+1]), the less the harmonic mix will match
> the wanted amplitudes.
Hmm, I suspect that this sames the cheby unsiutable for what we want, the
output from a guitar appears to be far fronm a sin.
> for the amp code, this would mean we should probably try the
> following: compress/expand the incoming signal to fit exactly into
> [-1, 1] (normalize). the coefficient tables need some treatment, too
> -- we want the output sum to be 1, and the relative strengths of the
> harmonics to match.
>
> i'm not up to understanding all implications of the fact that the
> incoming signal is not a pure sine; neither do i have a recipe for
> preparing the coefficient tables -- if we scale the individual
> coefficients by 1/sum their mix will not match what we want.
I think we should probably abandon the cheby approach for now, this
combined with the freqency dependency problem probably makes it a looser
:(
- Steve
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