[sdiy] Final VCA

[Tim Parkhurst]

On 3/7/06, Antti Huovilainen <ajhuovil at cc.hut.fi> wrote:
> Hi
>
> I'm looking for a circuit suitable as synth voice final VCA (low CV
> feedthrough, lowish noise). Low parts count, max one trimmer, linear CV
> (this is a must). Cheap too. Something that's still available in two-three
> years (when I maybe get the project done).
>
> What other options do I have besides LM13700 (which supposedly has pretty
> high CV feedthrough)?
>
> Is it possible to get discrete differential pair to work well enough with
> only one trimmer?
>
> THAT corp parts are not suitable due to cost & exponential control.
>
> Antti
>
> "No boom today. Boom tomorrow. There's always a boom tomorrow"
>   -- Lt. Cmdr. Ivanova
>

How about using the Analog Devices 2164? Its a quad exponential VCA,
but Charlie Lamm has schematics (and a PCB) that uses two sections to
get linear response.  This means you can get two, high quality linear
VCAs out of one chip (there are a few support chips involved, but you
get the idea). The 2164 is also available from Digi-Key. Charlie
apparently sells the PCB and the 2164, so here's a link

http://www2.charlielamm.com/synth/duallinearvca.php


Tim (high quality but not linear) Servo
--
"Imagination is more important than knowledge." - Albert Einstein