I appreciate everyone's suggestions thus far. Time to find my solder.

--- In Doepfer_a100@yahoogroups.com , "Tim Stinchcombe" <timothy@...>
wrote:

>
> There is nothing particularly special about the design, it is

simply

> one of the standard state-variable configurations, albeit using the
> inherent integrator action of a (compensated) op amp - it is to be
> found in at least one of the filter books that I have. The only
> real 'novelty' aspect in the Polivoks appears to be the use
> of 'programmable' op amps to provide a variable cut-off frequency.

It

> should be relatively simple to add another op amp in order to make
> the high-pass output available, and the method of setting the

current

> which 'programs' the op amps could possibly be improved, as the
> transistor-resistor set-up is dealing with some pretty small

currents

> (nano-amps), and I dare say is very sensistive to differences in
> individual components, perhaps making initial set-up tricky (but

this

> is pure conjecture, I've not tried actually breadboarding the

circuit

> to find out).
>
> Tim
>
> --- In Doepfer_a100@yahoogroups.com , <hardware@> wrote:
> >
> > We designed a Polivoks filter about one year ago but we stopped

the

> project
> > as Shawn Cleary of Analogue Haven informed us that such a filter

is

> under
> > development by the Polivoks inventor Vladimir Kuzmin. It should

be

> available
> > soon from Analogue Haven.
> >
> > Best wishes
> > Dieter Doepfer
> >
> >
> > > -----Ursprüngliche Nachricht-----
> > > Von: Doepfer_a100@yahoogroups.com
> > > [mailto: Doepfer_a100@yahoogroups.com ]Im Auftrag von mss_panzer
> > > Gesendet: Samstag, 2. Juni 2007 22:27
> > > An: Doepfer_a100@yahoogroups.com
> > > Betreff: 1 Filter Suggestion
> > >
> > >
> > > So when might we be able to see a Polivoks VCF Perhaps based

on

> the A-
> > > 124 design, with a HP/LP mix potentiometer and a solo BP pot
> > >
> > > Anybody have any thoughts on this
> >
>