[linux-audio-dev] Re: Cheby amp code

[Tim Goetze]

Steve Harris wrote:

>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.

if we normalize the incoming signal, apply the shaper(s), then scale
down, it just might work -- it will get the harmonic mix right at
least.

>> 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
>:(

yep, it doesn't seem to be getting easier the more we look at it.
the above approach could bring us close, but it does need xfading 
and two chebyshev shapers.

been thinking about how to do a hard clipper with sinc some more
today, without real results though.

tim