DIY Eurorack: The Power Supply (PSU) Prototype

Ergonomic, visual, size – there might be several reasons for creating your own Eurorack case. They are all applicable for me, but actually it’s more the way that is the goal. Deutsche Version

ClicksClocks Eurorack Power Supply Prototype

The first step to build my very own and unique case for my modular synthesizer in Eurorack format is taken. I finished the prototype of the power supply (PSU). As mentioned in an older post it is a copy of the original Doepfer PSU. To put it in nice words, I reverse engineered it. As several people mentioned this PSU might be the reference on the market for internal power supplies. I think the toroidal or ringcore transformer has clear advantages in case of low electromagnetic interference, which is important for audio usage, especially when you want to have a build-in power supply. One massive external PSU would have been an option, but I decided to build all internal with four supplies. Each delivers up to 1200 mA, which should be enough for a case of the same size as the Doepfer Monster Case.

PCB Layout for ClicksClocks Eurorack PSU

The PCB was created using Eagle. It was the first time I used this software and it is of huge benefit. I have a background in electronics and electrical engineering. But I completed my education over 20 years back. At this time we learnt everything from scratch, without any computer. Which means we had to glue the layout manually on transparent film.
In Germany we have the so called Dual Education System which gives you a solid basis in the particular field. I think I still benefit from it.
Anyhow, with Eagle it was pretty easy to create the layout. You start drawing the schematics, which is the logical basis for the PCB layout. Which is calculated and generated from the schematics. All you have to do is optimizing the layout. Be aware that your layout has to fit with the settings of your PCB supplier. Some suppliers offer their settings as download on their webpage. In my case this was Multi CB and they have a design guide, which is of great help for designing your PCBs with Eagle. In addition I had some very useful information from Dieter Doepfer. He was very supportive and gave me some details about the layer thickness of the PCBs for the power supply and the busboard. Thanks for that.
The Eurorack PSU board

Most of the parts were ordered at Distrelec. This company has online shops in many European countries. During the research I compared prices from most of the common online shops in Germany (Conrad, Distrelec, Reichelt, Voelkner etc.). Distrelec seems to have the best offer for most of the parts.
Here is an rough overview for most of the parts. A detailed part list will be send on request.

  • Distrelec – resistors, capacities, integrated circuits, potentiometers, terminals, leds, rectifier
  • Top Print – transformer and hardware
  • Reichelt – heat sink
  • Multi CB – PCB

After finishing the soldering the only thing you need to do is the adjustment of the LM 317 and LM 337 to the exact +12V and -12V, but that’s it.
All in all, if you don’t count all the hours spent on research, creation of the layout, soldering etc. all this is profitable for five boards. But be aware, if you have never used a soldering iron before it might be difficult to achive it. And even if it is only a copy, you will need to have some knowledge to understand what you doing. Sorry if this sounds a bit sententious.

If you need additional information please contact me or write a comment.

TECHNICAL DISCLAIMER: Please be aware that the power supply carries mains voltage (115 or 230 V AC). According to the safety rules the installation has to be done by qualified personnel only. Please keep that in mind: Danger to Life!
This is a private blog, and it is about sharing experiences. No warranty at all.

DIY Eurorack-Case, the Busboards

The prototype of the power supply is almost done. Just a few parts missing. Once it is completed it will be tested and the output voltages will be adjusted. I am curious to see if it works as expected. Some notes about the PCB. Before I ordered the boards, I send an email to Doepfer asking if it would be allowed to sell the superfluous boards. Dieter Doepfer answered me, yes I can sell the boards if I make sure that the boards are not from Doepfer and any warranty is covered by myself. He also answered some questions about the boards, which was very helpful. I think I will send him one of my PSUs to ask for permission again. I don’t want to get in trouble because I am copying his intellectual property.

ClicksClocks Eurorack Power Supply, almost done.

Time to focus on the next steps: The Busboard. My case will need eight Busboards. The PCB layout is finished for quite a while. It is a double layer board. The top layer is used as ground and the bottom layer has the traces for +12 V, -12 V, +5 V, Gate and CV. The layers are a bit thicker than usually, just to be on the save side. As some Eurorack modules need +5 V I decided to add a 7805 circuit to the board to be able to power them. The boards will be ordered soon.
ClicksClocks Eurorack Layout Busboard Detail

The rails and other parts for the case were ordered today at Gie-Tec. The four rows of the case are double 19 inch which adds up to a total 672 HP. The case should have wooden side-wings and an aluminium housing, which should be powder coated. This is the rough plan. More in short.

DIY Eurorack-Case, the Power Supply Boards arrived

The Eurorack Power Supply Board

Today the PCBs arrived and I had to start soldering one immediately. You will notice that the layout is similar to the Doepfer PSU. I tried to develop a complete own board but I have to admit that the design is compelling. The circuit uses the LM 317 and 337 adjustable regulators, they deliver the +12V and -12V, a ringcore transformer, a bridge rectifier and a few other parts. I tried several layouts with this parts, but the Doepfer layout is the best. I think they perfected it over the years. I know that my board is a copy though but it was still a lot of research needed to get all the parts together and finally create the layout. As I will need at least four PSUs, I decided to let the boards be produced by a company. But this only makes sense if you order more than 10 or 20 pieces. So I might have some “in stock”…
First I have to finish my prototype to see if everything works as expected. Then I will order the parts for the “serial” production.
Assembling the Eurorack Power Supply