# DIY Power Supply Thread - Questions and Help **URL:** \ **Category:** DIY STUFF\ **Created:** [January 27, 2020, 6:26pm UTC](https://lookmumnocomputer.discourse.group/t/diy-power-supply-thread-questions-and-help/117 "2020-01-27T18:26:23Z")\ **Posts on this page:** 1\ **Showing post:** 198
**Author:** ![fredrik](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/fredrik/32/682_2.png) [@fredrik](https://lookmumnocomputer.discourse.group/u/fredrik)\ **Post date:** [June 20, 2021, 10:08pm UTC](https://lookmumnocomputer.discourse.group/t/diy-power-supply-thread-questions-and-help/117/198 "2021-06-20T22:08:11Z")
An op amp cannot generate voltages outside its supply rails (most cannot even hit the supply rails). There are ways to generate a negative supply rail from a positive supply, but they require non-trivial circuitry (and/or non-trivial PCB layouts). I’d recommend getting a real supply, e.g. one of the frequency central ones. They’re cheap and easy to build and troubleshoot. See these threads for more pointers: > [@Power supplies choices?](https://lookmumnocomputer.discourse.group/t/power-supplies-choices/357): > > so im starting this topic as I get a lot of questions regarding power supplies, and there are a heck of a lot of options! the great thing is with this format is the power supply is the same as eurorack. so with that in mind. you can use the options open to eurorack. I guess it limits out things like the 4ms power as that has a eurorack power input module. but there are lots of options! the go to for me is the mfos style wall wart power supply and I always suggest either the wall wart one by mf… > [@DIY Power Supply Thread - Questions and Help](https://lookmumnocomputer.discourse.group/t/diy-power-supply-thread-questions-and-help/117): > > Power Supply Thread! For all of your Questions and Answers. Feel free to share all of your Power Supply Related Topics here! I will start with a Help Request. I am building a 9v Power Supply for reasons undefined that will be shared in this forum later, but I need to add a 7.5v rail. I figure I can do this with a [L78S75CV](https://www.st.com/resource/en/datasheet/l78s.pdf) and I am wondering what else needs to attach to the rail, any caps or diodes, etc. I ask for assistance so I do not make any grave mistakes, since this is deali… (might move this post to the latter in a bit) --- _[View the full topic](https://lookmumnocomputer.discourse.group/t/diy-power-supply-thread-questions-and-help/117)._