[sdiy] 4 Pole state-variable filters

[Scott Bernardi]

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 - - -
> -  h t t p : / / w w w . u g w a r e h o u s e . o r g /  -
> --<T h e  P r o t e u s>-<Musician>-<Producer>-<Engineer>--

--
Scott Bernardi
sbernardi at attbi.com