[sdiy] State-variable VCF issue

[patchell]

    If you look at the State Variable Filter in this document:

http://www.silcom.com/~patchell/smb1/smb.pdf

    It is on Page 19.

    U72A is used to control the Q (resonance) of the filter.  I provide
an option to run the input of the filter through this OTA, which will do
what you describe below with pots.  However, I generally find that this
makes the filter sound somewhat "thin".  Sounds better making
distortion...

Tim Ressel wrote:

> Hey gang,
>
> My state-variable filter seems to clip alot and do
> other nasty things. I recall the old Paia 4700 series
> filter used a dual pot for the Q control with one
> section attenuating the input as the Q is increased.
> This had the effect of keeping the resonant peak at
> the center frequency from clipping. I would like to do
> something like this, but I have voltage controlled Q
> with a 3080 replacing the Q pot. Has anyone seen a
> circuit that say uses a second 3080 on the input? I
> don't know if the sense of the current for the input
> 3080 would be the same or opposite that of the Q 3080.
>
> Help??
>
> --Tim
>
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--
 -Jim
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