I still don't see what the vactrol is for. What is driving it, and to what end?
Sorry, didn't see the question. Nothing is driving it in the schematic, but if you use one like pictured in the first post it just has an LED as the light source. Crudely, hang a resistor on it to limit the current and a rheostat-wired pot to vary the amount of attenuation (note the LDR jumper remains
unconnected, not connected as the proto board screen layer implies).
In testing it, I used one of my own power supplies and just took the negative rail, a resistor and varied the LED with the voltage control on the power supply board.
Yeah, thanks for that document [silent:arts]! Most of it is available on the Waltzing Bear site and I seem to remember seeing those handwritten pages elsewhere but can't remember where I found them either.