I spent a bit of time raking through my box of bits, trying to figure out what I was up to earlier in the year. I’d been planning on building a MFOS WSG, but got distracted by the Super Simple Oscillator. I think I’d decided to build a few to go alongside the WSG, two banks of three (low, mid, high), each bank with it’s own simple RC filter.
Looking through a spreadsheet of parts ordered and parts still needing ordered, it looks like I was planning on adding the Channel A & B Zany Oscillator Trigger Out to my WSG build. I think the plan was to feed this into the SSO’s via a vactrol as outlined in:
By the looks of things, I was assuming that I could patch this CV into all three SSO’s in a bank, rather than having a singular CV input for each SSO. Is that a thing…? Or do I need a separate CV input for each SSO, and a CV multiplier module…?
To start with, the trigger out circuit you’ve linked produces something that’s not intended as a control voltage but a trigger — it’s either on or off, and it’s on for only a brief moment at the start of each cycle of the oscillator. So in the best case if you tried to use it as a pitch control voltage it’d only affect the pitch value very briefly. The duration of the output pulse is on the order of RC = .047 µF x 100k = 4.7 ms — a very brief blip indeed. Probably not what you want.
But to drive a vactrol you need a current on the order of 10 mA. The trigger out produces a voltage; to get a current you need to put its 5–7 V signal through a series resistor. To get 10 mA you need R = (5 to 7 V)/.01 A = 500 to 700 Ω. (Might vary somewhat depending on the vactrol LED and LDR.) Vactrols are slow, though, so trying to get one to respond well with a 5 ms pulse is not likely to work well.
If nevertheless you go ahead and put a 500 Ω resistor to the LED to ground, that’s in parallel with the trigger out’s 100k resistor to ground. It’s so much smaller a resistor (1/200th of 100k) the 100k will hardly matter. With the vactrol added, as soon as the LED starts conducting the RC time becomes 200 times shorter! About 24 µs. Almost certainly not what you want and almost certainly nothing the vactrol can deal with gracefully.
A way around the resistance problem is to use an op amp as an LED driver; then you can send the output of the trigger to the op amp and it’ll cause the LED to light up without changing the trigger’s RC. But again, with this trigger output, the pulse duration is probably too short.
As for your actual question, if you have multiple vactrols driven by op amps, then a single control voltage source could be connected to all of them and it ought to work. But trying to drive multiple vactrols directly with a control voltage, rather than via op amps, is going to be very problematic at best.
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Thanks for the detailed reply! It sounds like I was barking up the wrong tree, possible in the wrong forest. I think we’ll just ditch that plan and have the WSG and the SSO’s as separate modules that output to the same place. That’ll save me a fortune in vactrols… 
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