[sdiy] Moog filter maths

[Rob B]

Honestly, with ram being so cheap these days, it might actually be easier to
just do a matrix of the various waveforms of a moog filter or whatever and
just interpolate for the various settings between the knob changes.
Basically, do a big multisample.. Maybe even with that you could somehow
figure out what is happening rather than trying to do it mathematically,
which would lead you into some treacherous and time-consuming code that
still might not work all that well. I mean, at low signal levels, you start
even noticinig effects produced by layout, grounding, etc, that make one
moog filter version sound different than the last, and, as far as the 303 is
concerned, its such a piece of junk that you can line up any 3 or 4 of them,
put them on the same settings and end up with completely different sounds.

There is quite a bit of reason to believe that matriculation of samples is
what they do on rebirth. (no pun intended btw ;) reason-rebirth? hehe..

Esp when you look at the waveforms on a scope.. Rebirth becomes *very*
suspicious at that point, and for a 303 you only have 6 knobs, so its rather
easy to emulate in that manner.

Still, by using various filter models in a piecewise method, you might be
able to do it. Watch what the filter acts like at various points, then use a
filter that behaves in that manner until some point, then interpolate
between that model and the other.

I doubt you or anyone else will *ever* figure out the empirical calculations
that will deal with every variable within a moog filter, but, if you do,
while you are at it you can prlly finish up Einsteins unified field equation
too. ;))

Rob

----- Original Message -----
From: matti <matti at devo.com>
To: Synth DIY LIST <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, October 27, 2001 9:06 PM
Subject: Re: [sdiy] Moog filter maths


> On Sat, 27 Oct 2001, Paul Maddox wrote:
>
> > Dear all,
> >
> >   Is there anyone who's been mad enough to do the maths for the moog
ladder
> > filter?
> >
> >   Im learning DSP, and Ive been told its impossible to do in a DSP..
> >
> >   I take the word impossible as a challenge!
> >
> >   Probably best to reply off list :-)
>
> Actually, I'm quite interested in what can be come up with. I don't know
> alot about DSP But I'm trying. Certainly there are others on sdiy that
> want to talk about.....sdiy.
>
> -
> the bills were all due yesterday
> you've failed
> you're through
> you've failed
> you're through
>