Doepfer

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: [Doepfer_a100] 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?
> >
>