# Need help with first Diy VCO to eurorack **URL:** \ **Category:** DIY STUFF\ **Created:** [December 29, 2023, 5:14pm UTC](https://lookmumnocomputer.discourse.group/t/need-help-with-first-diy-vco-to-eurorack/6835 "2023-12-29T17:14:33Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![flikker](https://avatars.discourse-cdn.com/v4/letter/f/8baadc/32.png) [@flikker](https://lookmumnocomputer.discourse.group/u/flikker)\ **Post date:** [December 29, 2023, 5:14pm UTC](https://lookmumnocomputer.discourse.group/t/need-help-with-first-diy-vco-to-eurorack/6835/1 "2023-12-29T17:14:33Z")
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 ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [December 29, 2023, 5:44pm UTC](https://lookmumnocomputer.discourse.group/t/need-help-with-first-diy-vco-to-eurorack/6835/2 "2023-12-29T17:44:05Z")
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`. ---
**Author:** ![flikker](https://avatars.discourse-cdn.com/v4/letter/f/8baadc/32.png) [@flikker](https://lookmumnocomputer.discourse.group/u/flikker)\ **Post date:** [December 29, 2023, 6:06pm UTC](https://lookmumnocomputer.discourse.group/t/need-help-with-first-diy-vco-to-eurorack/6835/3 "2023-12-29T18:06:04Z")
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+ ? ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [December 29, 2023, 6:39pm UTC](https://lookmumnocomputer.discourse.group/t/need-help-with-first-diy-vco-to-eurorack/6835/4 "2023-12-29T18:39:36Z")
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. ---
**Author:** ![flikker](https://avatars.discourse-cdn.com/v4/letter/f/8baadc/32.png) [@flikker](https://lookmumnocomputer.discourse.group/u/flikker)\ **Post date:** [December 29, 2023, 7:19pm UTC](https://lookmumnocomputer.discourse.group/t/need-help-with-first-diy-vco-to-eurorack/6835/5 "2023-12-29T19:19:04Z")
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](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/7/e/7eb47f5d98f2d211e42e702389bf8906d608e5f8.png) thanks again ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [December 29, 2023, 9:21pm UTC](https://lookmumnocomputer.discourse.group/t/need-help-with-first-diy-vco-to-eurorack/6835/6 "2023-12-29T21:21:50Z")
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. ---
**Author:** ![flikker](https://avatars.discourse-cdn.com/v4/letter/f/8baadc/32.png) [@flikker](https://lookmumnocomputer.discourse.group/u/flikker)\ **Post date:** [December 29, 2023, 11:22pm UTC](https://lookmumnocomputer.discourse.group/t/need-help-with-first-diy-vco-to-eurorack/6835/7 "2023-12-29T23:22:30Z")
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.