[sdiy] CV-vactrol circuit

Scott Gravenhorst music.maker at gte.net
Fri Jul 3 23:09:01 CEST 2015

<niroke at tampabay.rr.com> wrote:
 >I'm trying to add external control to my TR-9090's voice
 >parameters, and I'm sure if that was as simple as patching in to
 >a CV summing point, it would have been done by now. The 909
 >circuits don't lend themselves to voltage control. From what I
 >know, I can control the parameters with a vactrol in series with
 >the variable resistor. If you have a better solution, I'm eager
 >to hear it!

Have you looked at H11F1?  They might be a lot more cosistent from unit 
to unit and it's basically the same thing as a vactrol, just that it's 
an LED that shines onto a MOSFET transistor.  They will handle AC signals.

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