[sdiy] CV-vactrol circuit

David G Dixon dixon at mail.ubc.ca
Sat Jul 4 03:34:05 CEST 2015

Niroke, I simply cannot imagine trying to do what you are trying to do,
without a basic understanding of voltage, current, and basic circuits.
These things are usually not solved by trial and error without some
underlying knowledge of electronics.

If you already have that knowledge, please excuse my impertinence.  However,
if not, then I would spend some time boning up on basic circuits before
trying to do what you're trying to do.

> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl 
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of 
> niroke at tampabay.rr.com
> Sent: Friday, July 03, 2015 4:16 PM
> To: Synth-diy at synth-diy.org; Gordonjcp
> Subject: Re: [sdiy] CV-vactrol circuit
> Gordon,
> I have no experience with anything digital, but if you mean I 
> could have panel settings and midi control over parameters, 
> that could work.  I'd have to have someone walk me through it 
> all.  I was trying to stick with CV because I have a 
> decent-sized modular and several MIDI/CV interfaces including 
> an MCV24.  
> Neil,
> It was my understanding that the two trimmers in the vactrol 
> circuit allowed one to adjust the CV to only swing to the 
> desired resistance.  Most of the vactrols I've seen go up to 
> several megaohms. 
> ---- Gordonjcp <gordonjcp at gjcp.net> wrote: 
> > On Fri, Jul 03, 2015 at 08:58:51PM +0000, 
> 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! 
> > > 
> > 
> > You could try digital pots, maybe?  Does it *have* to be a 
> control voltage?
> > 
> > --
> > Gordonjcp MM0YEQ
> > 
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