Need help with first Diy VCO to eurorack

DIY STUFF
1

Hey, I’m fairly new to modular synths and building diy components, I learned to build the Reverse avalanching oscillator (super simple osc) and it worked after a while on breadboard now soldering everything on a plate.
Now I was always powering the oscillator via 2, 9volt batteries in serie, but I want to connect it to a 10pin (or 16PIN? I think is overkill?) power cable so I can connect it to my eurorack power supply via a 10 pin to 16pin cable.
The 10 pin connector has 3 GND connections, 1 +12v and 1 -12v, what is the difference between the Ground and the -12v? and where do I connect the + and - I connected earlier to the batteries? I’m confused can someone clear things up for me??

Thank you very much in advance

2

Voltages are measured relative to ground, so +12 V is 12 volts above ground and -12 V is 12 volts below ground. The voltage difference from +12 V to -12 V is 24 V.

If you were using 2 9 V batteries in series presumably that’s because you’re using a transistor that needs more than 12 V to oscillate. But you should be able to connect what was connected to battery + to +12 V and battery - to -12 V. That will give a total of 24 V across the transistor+LED, versus your previous 18 V; should work but might behave a little differently than it did.

However if you have an output jack whose sleeve terminal formerly was also connected to battery - it should now be connected to ground.

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3

Wow, thank you so much for a fast answer! You’re the man.
However, it’s not entirely clear because my battery- is the same as my ground in my circuit, wouldn’t it also work to just connect the ground to ground and +12 to battery+ ?

4

Then you’d have only 12V across the transistor and LED. With some transistors that will work but some need more than 12V. Try both ways.

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5

There is just one thing I don’t understand here and that is that I don’t know where to connect my audio output jack now, because I don’t have a separate ground and -12v in my circuit? I’m still a bit confused, using exactly this circuit:

Schermafbeelding 2023-12-29 om 20.18.28
Schermafbeelding 2023-12-29 om 20.18.28862×454 146 KB

thanks again

6

In your existing circuit there is

  • a higher voltage (+18 V)
  • ground (0 V)
  • and a lower voltage (0 V, the same as ground)

Transistor+LED connects between the higher and lower voltage and output jack connects between output and ground.

With Eurorack power, you could try the same thing but with +12 V for the higher voltage. But if that isn’t enough to make it oscillate you can use

  • a higher voltage (+12 V)
  • ground (0 V)
  • and a lower voltage (-12 V)

and again, transistor+LED connects between the higher and lower voltage and output jack connects between output and ground.

7

Okay! haha this felt kind of stupid on my part but I think its clear now
Gonna try it out now with a -12v and ground. Thank you so much.