Passive volume pedal controlled by cv?

[durwin]

So I'd like to build a volume pedal in a small enclosure to be controlled by a Moog MP-201 - seems counter intuitive I know but it means I can get LFO's in to it etc.

The catch is, I need it to be a passive system so that it doesn't screw with my fuzz impedances...

Any thoughts? 

[Mark Hammer]

Simplest thing is to use a CV to drive an optoisolator.  The CV lights up an LED which makes the input leg or ground leg of a virtual voltage divider drop its resistance.  That's often how many compressors work, like this one: http://dt.prohosting.com/hacks/what1.gif

[PRR]

Welcome.

Any volume control screws with impedances.

[ElectricDruid]

What Mark said. Something optoisolator/vactrol-based is as close to passive as you'll get and still have CV control.

Otherwise, you'd be looking at some active way to control volume with a CV - a VCA of some type, perhaps a 13700 OTA, or something discrete, like the Minimoog design (which would be appropriate, at least for your application!)

T.

[wavley]

What Mark and Paul said.

Take a look at the Moog MF Boost, it has CV control for the Gain knob, I use an old DOD FX17 because it has a CV out with mine.  For all intents and purposes it's a volume pedal for me because it's always on (I like the tone control), you can set the minimum with the gain knob and sweep up to maximum.  I keep my stuff that want to see a pickup before that or I use the Jack Orman pickup simulator circuit and then they don't care about buffers or wah pedals and play nice with everything.