Troubleshooting 1v/oct VCO

I’ve been having some issues getting Sam’s 1V/octave VCO module to work, and haven’t found much written about it on the forum. As far as I can tell the saw, and triangle waves both work fine… the square wave not so much :sweat_smile:.

Slightly adjusting the pulse width or PWM knobs causes the square wave to cutoff completely. My guess was that the value of the pots used for these two knobs needed to be adjusted, but I swapped them out several times with different resistor values, and nothing changed. The other problem is that the CV for the PWM doesn’t seem to have any effect on the pulse width.

Have any of ya’ll run into similar issues while trying to build this module?

I did. Check your grounds, make sure you doint have any ground loops near pots or otherwise. This is almost for sure your issue. Triple check the wiring, and make sure everything that needs to be to ground is.


I checked the circuit again, and I didn’t see any ground loops. I see the schematic says to connect the cv in and pwm in to the tip of the jack socket. Should the sleeve of each jack socket be connected to ground?

Yes they should.____

Thanks! Maybe it IS just a ground loop i haven’t found then. My circuit is a bit of a rat’s nest.

Checked it again this morning, and found what was causing the problem. Turns out I put a 470R where there was supposed to be a 470k resistor.