SergeModular

They are Serge's own OTA design. The small OTA assemblies (we
called them "clones") are a givaway, and these are on all those
latest filter designs. This is the same circuit that Serge used in
the VCAs (hence, "cloned") and I packed it into this small module
(kinda laughable by today's standards) at Serge's constant
prodding: "Make it tighter, tighter!" Don't know if someone has re-
laid those out --they certainly were a candidate since they were
very hard to unsolder or repair. The transistors were very tightly
matched with our own in-house calibration unit.

--- In SergeModular@yahoogroups.com, "John Loffink" <jloffink@a...>
wrote:

> State Variable designs since all three filters provide low, high

and

> bandpass outputs. More than likely they use OTAs for the voltage

control

> circuitry.
>
> John Loffink
> The Microtonal Synthesis Web Site
> http://www.microtonal-synthesis.com
> The Wavemakers Synthesizer Web Site
> http://www.wavemakers-synth.com
>
>
> > -----Original Message-----
> > From: kirkdegiorgio [mailto:kirk.degiorgio@b...]
> >
> > I've been doing some newbie research into the actual circuits of
> > VCF's and wondered what design the Serge filters are based

around?

> > I've read some brain-boggling facts about diode ladders,

transistor

> > ladders, sallen-key, OTA based designs, etc but am not much the

wiser

> > lol... but out of curiosity what category would the Serge filter
> > designs come under?
> >