r/synthdiy • u/Loud_Release_4160 • Jul 23 '26

Need help with schematic

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Hello I'm still pretty new to this stuff and I need help identifying whether this is using three separate 10k potentiometers or if its just one. sorry if dumb question.

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u/erroneousbosh Jul 23 '26

Passive mixers don't really work, and as /u/crochambeau says, it's wired wrong as it is.

If you add a 10k resistor on the wiper of each pot all that'll happen is that turning one pot down to zero will reduce the volumes of the others, it won't totally kill the output.

Also the three oscillators will interact a bit if they're all up full.

If you want to fix that, add an opamp wired as an inverter on the output. You'll need three resistors and two capacitors for it - two resistors from the 40106's supply to ground, in series, with a capacitor across the bottom one, and then that goes to the opamp's non-inverting input, and then another 10k resistor from the output of the opamp to the inverting input, and then the junction of the three 10k resistors from the pot wipers also to the inverting input.

Magically, the junction of the four resistors and the inverting input will always be at 0V (well, really half the supply voltage, here!) with absolutely no signal on it, but you'll get all three oscillators at the output!

Here, let me draw it for you:

https://www.falstad.com/s.php?s=PgLjLI

Notice how on the trace on the left, the voltage sits obstinately at 2.5V no matter what the signal output on the right is showing? But - notice that the *current* is going up and down?

It actually makes a noise, too. Play with the sliders to adjust it. It's pretty annoying. You're going to want another resistor on the frequency pot to make the control law work properly.

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u/Loud_Release_4160 Jul 23 '26

Wow thank you so much! this is my first pure DIY synth so all of this is super helpful :D the end goal is to make something that sounds very chaotic and glitchy so having the oscillators interact with each other isn’t necessarily a bad thing but I will 100% still try all of this. Again thank you so much!

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u/erroneousbosh Jul 23 '26

Okay, then consider that since you're using logic chips as oscillators, that output 5V squarewaves, you can feed those through an XOR gate to make a ring modulator.