[sdiy] mixing poles

[Grant Richter]

The Wiard Boogie Filter does this using fast Vactrols. The diagram  
even shows the OTAs as resistors, duh.
You will need to add inverters on the 12 and 24 dB outputs like the  
original b2 and b4.
Here is the original schematic, you could use the CEM chip and just  
replace the 4051stuff with a 4 input mixer.

http://www.musicsynthesizer.com/Circuitry/Multi-Function%20VCF.htm

On Dec 6, 2006, at 12:48 PM, David Moylan wrote:

> Has anyone here done any work mixing the individual pole outputs  
> from a
> 4-pole LPF?  I came across information about the Oberheim expander
> multimode filter and the idea looks really interesting.
>
> http://www.emulatorarchive.com/AM/AM3000/AM3372/am3372.html
>
> The Oberheim uses discrete settings which I'm guessing is to  
> facilitate
> patch storage, but theoretically you can just use a 4 input mixer  
> and go
> nuts.  Or maybe there are only so many combinations that might be  
> useful
> (but who's to say what's useful).
>
> Something rings a bell here with the Oakley Superladder, but I don't
> have a schematic.  Tony?
>
> Dave