Computer PSU for pedals?

EricssonB · #1 12-09-2012, 03:22 PM

Does anybody run a computer PSU to power their pedal chains?

Sounds like plenty of overhead and good power.

I don't see a problem with it. All of my pedals run fine on 12VDC, and should I come across one that needs to be throttled down, then I could put a resistor on the plug. Not a big deal.

Aaron_D · #2 12-09-2012, 03:23 PM

Are you modding it? There are no barrel type connections on a typical PC power supply.

EricssonB · #3 12-09-2012, 03:26 PM

Quote:

Originally Posted by Aaron_D

Are you modding it? There are no barrel type connections on a typical PC power supply.

Oh, of course.

Jazz Ad · #4 12-09-2012, 03:45 PM

A typical computer PSU goes for 300 watts. With the loss in voltage conversion it gives you roughly 30A in 9V, which is about 30 times whay you need.
They use a fan which makes noise, can get stuck and overheat. Filtering a lot of air at ground level isn't a very good idea either.
The case is pretty thin and if you step on it it is likely to get damaged.
You will need to modify the hell out of your power supply to get 9v from 12v and properly control the power supply with a step controlled switch like the ones used in pc case.
A PSU delivers unfiltered current on the 12v rails, which means noise. To use it for audio you need to add filters. It uses common grounding which for pedals must be avoided every time you can.

The real question would be, why would you bother using a tool that wasn't designed for your task, when there are excellent readily available solutions to power your pedals?
What's the goal?

oerk · #5 12-09-2012, 03:54 PM

Echoing Jazz Ad's advice. It's really not the right tool for the job.

That said, I'm using a 19V/2.3A laptop power supply, with 7809 and 7812 voltage regulators with very good results. This gives me clean 9V and 12V rails at 1A each.

Jazz Ad · #6 12-09-2012, 03:57 PM

A laptop power supply is completely different. Much closer to our needs.

EricssonB · #7 12-09-2012, 04:01 PM

Quote:

Originally Posted by Jazz Ad

The real question would be, why would you bother using a tool that wasn't designed for your task, when there are excellent readily available solutions to power your pedals?
What's the goal?

I have a bunch of pedal warts and would like to power them with one power supply, and I just happen to have a PSU laying around. Figured why not.

Sounds like I should just grab a dedicated unit for ~$20.

¯\( ツ )/¯

Quote:

Originally Posted by Jazz Ad

A laptop power supply is completely different. Much closer to our needs.

I have one of these laying around!

delta7fred · #8 12-09-2012, 04:29 PM

PC power supplies need a load on (at least) the +5V supply to work correctly. About 1 amp seems to work ok (4.7 ohm 10 watt resistor on a suitable heatsink).

The old AT power supplies turned on/off by switching the mains supply.
Edit. yours is one of these.

Reducing the +12V to +9V within the box is not an easy (or safe) exercise and while you could do it externally with one or more 9v regulators (LM7809 etc) you might as well build an analogue power supply from scratch rather than messing with switched mode stuff.

Or buy one designed for the job!

Edit
Laptop supply is much better but still needs bringing down to 9v.

Bakkster_Man · #9 12-10-2012, 07:43 AM

Going to echo that for the effort to modify a PC power supply to do 9V, you might as well build your own isolated power supply. That's the big issue, is that every output of a PC supply will share the same ground, beyond the overkill factor and the need to still regulate the voltages down to 9V as well. It might also be incredibly noisy power, since I believe most PC supplys use a switching power converter for efficiency, which wouldn't be suited for musical use.

Grab a multi-tap transformer and toss it in the same case so you have isolated power. You would at least be able to reuse the AC input, some caps, and the case.