Test Gear

Eurorack module prototyping and testing power supply thing: Part 1

I was looking at my workbench not too long ago


And I thought if I had a ‘real’ power supply with banana jack connectors most of this rat’s nest would get cleaned up. In addition to the mess, the ATX supply + converter board has some other problems. Most notably that the 24 pin cable is fairly stiff which pushes the converter board into the work area and since the ground and power terminals are close to each other this makes it easy to short and I have blown a couple of fuses on it. Now if I was sane I would pick up a used HP3630. It’s a pretty typical triple output power supply perfect for prototyping a euro rack module. However I’m just a little crazy so I’ve decided to build my own.

Let’s see how far I get before I decide to go buy an HP3630.


The basic design is to output three voltages: +12 V, -12 V, and +5 V. Output connections will be made via banana jacks and a 16 pin IDC connector the same the would be used to power a euro rack module in the rack. The point of this project is to reduce the three intermediate steps I use now to a single step. So the power supply should plug directly into the wall with all of the associated fun stuff that implies.

Everything above can be handled with a ±12 V output switching supply and a regulator to get 5 V. So I decided to add current measurement and display for each of the output voltages.

Design – Switching supply

To start designing a switching supply is going to be way to complicated for this project so I decided to purchase one. Based on my previous experience with Meanwell supplies I picked a ±15 V dual output supply. Using 15 V instead of 12 V means that any opamps used as part of the the current measurement won’t have to run on the high rail; as well as, allowing any output irregularities to be trimmed out with regulators.

The Case

Now that the switching supply has been chosen and get a rough idea of how big of a case to use for the project. I picked a ~20x15x7 cm case and stared drilling.

Next time we’ll take a look at regulation and the display.

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