[sdiy] Synthancon VC-Resonance

[John Luciani]

On 5/2/06, nathan settembrini <nathansettembrini at gmail.com> wrote:

> Hi,
> I am doing a project for the Theory of Music Synthesizers class at Georgia
> Tech.  We have put together the Synthacon VCF filter
> (http://www.cgs.synth.net/modules/cgs35_syntha_vcf.html )
> and are trying to add voltage controlled resonance to the circuit.  We have
> tried using a JFET as a voltage controlled resistor to replace the pot but
> think we were overdriving the amp and getting a lot of noise.  The other
> thing we tried was using a Vactrol to replace the pot, but can't figure out
> a way to get the resistance low enough (without supplying rediculous amounts
> of current) to replace the 1k pot.  Does anyone have any ideas?

There is probably a way that is more clever but a voltage controlled
current-sink is
a trivial circuit to make and should be able to replace the pot.
Requires an op-amp, a couple of resistors and an N-channel FET.

If you look in the "Load Schematic" section of the document at

http://www.luciani.org/geda/util/matrix.pdf

you will see a schematic for a circuit called "Load Cell" which is the
current sink.

(* jcl *)

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