Yes, that'd be the best place for it.Attached is a modified #37 to determine where to put the SW1 reset capacitor. I would bet on to the left of the resistor
Depends on the unit. Read this for more info.Can i use 2 - 12v units connected together in series as a dual voltage unit?
Where are you located?i'll see what single 12v power suppliers they have.
Even with single supply, requiring two op amp channels per control, you can build two controls per board with a quad op amp like you were talking about before, if you want.One conrtol per ic keeps is simple and should not affect const much.
That is a decoupling capacitor, a universal requirement for analog circuits. The general rule is one cap to ground per IC power pin, located as close as possible to the IC and with short leads. In you case one of the power pins already is connected directly to GND, so one cap per part.Circuit #29, on the upper right of the drawing, showes a capacatior between gnd and +12v..
Does that mean I install one at the soruce?
The LM324 will work fine. It's a somewhat mediocre amplifier but you're just using it as a switch anyway, so nothing to worry about there. And you can order cheap PCB's from a site like jlcpcb.searching for parts.
I decided to use a quad op amp to save cost of pcb and socket.
Is LM324M the correct one?
What should i search for to get the printed circuit board?
Yeah, I mentioned this approach (using 555'5) in post #28 but no one picked up on it.Here's another version using a CD4069 inverter.