[sdiy] 4 Pole state-variable filters

[greg montalbano]

Ya, I built that puppy some years ago, and can recommend it highly.
Sorry I can't donate any details (don't have my construction notes any more),
  but it's definitely worth the trouble -- you get a pretty good education 
in multi-mode filter construction, and a fine piece of hardware (didn't 
sound like anything else modular that I had at that time).
One thing I COULD offer is to scan the article that came with the schematic
(was part of the SSM DATA BOOK for 1979).

~GMM

At 09:09 AM 2/10/02 -0800, you wrote:
>There was an article by Bob Chidlaw in EN #99 that had a nice design for a
>4pole state var, with a dual feedback scheme ("Q" and "R") that gave dual
>peaks.  His design used a SSM2040 filter chip, I have a partial schematic
>(no control circuitry, opamp pinouts not marked) using LM13600's. I haven't
>tried it yet, so maybe you can be the guinea pig.
>Note that RV1 and RV2 are dual pots, configured to simulate reverse log
>pots. Also, you might want to put some trimpots feeding the + inputs of the
>OTA's for control rejection.
>http://home.attbi.com/~sbernardi/elec/4polestatevar2.pdf.
>
>The Proteus wrote:
>
> > Hello all,
> >
> >         Are there any good references in text or online on 4-Pole
> > state-variable filters? I'm finally getting back into design, and would
> > like to construct a filterbox that has HP, LP, and BP outputs, and would
> > hate to build up discrete sections for each filter. I've got both the
> > Musical Engineers' Handbook and the Electronotes PCC at my disposal, as
> > well as Chamberlin. Any help would be greatly appreciated.
> >
> > Regards,
> >
> > Proteus
> >
> > - - - T h e  U n d e r g r o u n d  W a r e h o u s e - - -
> > - - - Subversive - Tools - For - A - Chaotic - Planet - - -
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>
>--
>Scott Bernardi
>sbernardi at attbi.com