[sdiy] What would be THE best, most versatile VCF available on DIY community ?

[David G Dixon]

> this is something that has long bothered me...when looking at 
> schematics that use the CEM chips or SSM chips, is it 
> possible to simply transfer the entire design to OTA's? 
> (13700s) or is there some sort of MAGIC (something in the 
> patent?) in those chips which makes them hard to copy?
> 
> for instance.....the Anderton Multiple Identity 
> Filter...could you make the same thing with OTAs? in his 
> introduction he mentions making it with SSM chips instead of 
> CEM chips...I took that as a good sign.

There's no magic.  Any filter can be made with OTAs and buffers (or VCAs and
integrators).  The key (and I say this not to sound like a pedantic jerk,
but simply because it is true and never fails if you know how to use it) is
to derive the transfer function of the filter you're trying to emulate and
then use algebra to figure out where to put the various inputs and outputs
and feedbacks in your own version of it.