Subject: Re: [linux-audio-dev] [ann] unmatched - a LADSPA amp tone
From: Tim Goetze (tim_AT_quitte.de)
Date: Thu Oct 24 2002 - 02:50:29 EEST
Steve Harris wrote:
>Stacking the valve plugins is the key to making them sound interesting.
ah, now i dig it. maybe you could make a note about the intended
use in the valve doc?
>> i've copied (950 + 50 silent) samples of each into
>> http://quitte.de/fender-sine.wave -- the quitte.de quota is
>
>Cheers. Just looked at it. It was what I was expecting from your
>description.
good. do you think the 44100/12 oscillation is a speaker
or output transformer effect?
>> >Infact, this should just happen, if you use the crossover plugin and
>> >put the output through your speaker cone IIR you should see a similar
>
>> yup, it definitely looks more like it on the scope. but the
>> aliasing the crossover introduces is simply unbearable. i think
>> i'll go for a ride and show some waves to the guy who fixed my
>> fender amp recently, he knows a lot about the circuitry.
>
>The crossover plugin was a shot in the dark, based on a vague description
>of the effect by someone who understood the electronics. Now I have seen
>your recording, and have applied some brain power to it it's obvious what
>I did wrong, and how to fix it.
now i've seen your code i know where a good deal of
what i have called aliasing is from. :)
did you mean to start the sample loop at index 1 in
crossover_dist_1404.xml? 0 sounds much better. i'm
afraid it still aliases a little, but it does look
like it's basically doing the right thing iiutc.
the problem with both the valve and the xover i think
is that the further you drive them, the edgier the
discontinuity gets. it would have to be computed at
sub-sample resolution, and interpolated in a band-
limited fashion for the real 'hard driving' i think.
my reasoning is that the problem we are facing here
is the same as in the generation of band-limited
square (or sawtooth, if you will) oscillation.
tim
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