> me like to see a MOTM filter similar to the Buchla 292? As you Buchla heads
> probably know, the Vactrols in the 292 give it that wonderful "plucked,
> woody sound." I have the MOTM 410 VCF which utilizes the Vactecs, but this
> module is set up more like a phaser than a conventional VCF.
> I thought it would be great to have a simple Vactrol based VCF with the
> typical FREQ, RES, controls. Any ideas?
Personally I love vactrols in phasers and in the 410, but I ∗hate∗ them in ordinary
filters. I once built a clone of the Buchla Lowpass Gate (switchable from VCF
to VCA and something in between), and it has Vactrols, and it has these "certain
qualities". But it is so outright ∗annoying∗ when you want to do snappy envelopes
and it's just not possible. You just cannot cut off this darn release tail.
Any ideas? Two:
(1) Get a fairly good approximation with a VCLAG in the CV path to the filter.
This is not a perfect emulation, because the Vactrol's time constant is nonlinear,
but try it and see if it isn't good enough for your application. (And, as the LAG
is a VCLAF, you can also emulate some of the nonlinearities by feeding the CV
to the VCLAG's signal input ∗and∗ the VCLAG's CV input.)
(2) Rather than making each and every filter in a Vactrol-based and a Vactrol-less
version, we could make an extra "VACTROLIZER" Module: A CV processor that
runs the CV thru a real Vactrol circuit to get a CV output signal for modulating
any filter you want.
The 2nd option is something I have not built yet, but which I will surely do in
the near future.
JH.