Subject: Re: [linux-audio-dev] Re: Cheby amp code
From: Tim Goetze (tim_AT_quitte.de)
Date: Mon Nov 04 2002 - 14:54:56 EET
Steve Harris wrote:
>On Sun, Nov 03, 2002 at 07:48:55 +0100, Tim Goetze wrote:
>> >OK, why do they use two shapers? Or is it one cheby and one non polynomial?
>>
>> two chebyshevs, blend factor depending on incoming amplitude.
>
>Thats interesting, cos liiing at your waterfall plot it doesn;t seem liek
>that should be enough.
afai understand the paper, they've been doing this as an academic
exercise. ivory towers and so on ...
>I odnt think that Line 6 and co. are using chebys, I think there using
>something more like our first attempt. That's not based on any knowledge
>or anything, just a hunch.
yep, it seems unlikely the more i think about it. the peak
problem when lots of strong harmonics are generated could be
tackled with a phase-shifting filter. but we'd still need to split
the input into multiple bands to come up with purer sines (i've
done some more experiments with two mixed sines and a chebyshev
shaper: the output is badly garbled, with unpredictable peaks).
but pod distortion waveforms don't look like they use chebyshev
polynomials at all.
tim
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