Eurorack Power Guide

Power can be tricky. Most of us come to modular having never used a bi-polar power supply, and now we have to measure and understand the dark art of power. To try to clear up this confusion, I’ve written this Eurorack power guide. That said, I am not an Electrical Engineer, so you are taking your safety and your system into your own hands.

Wiring

How you connect the power supply to your bus board or modules is up to you. The Eurorack Power Supply has three outputs that are available at any time. Here are the three outputs and common use cases.

Eurorack Power Supply

This is the most common use case, in which the wire pads are soldered to a buss board.

Eurorack Bench Supply

Here, the 10 pin connector is used as a Eurorack bench power supply.

MOTM Power Supply

Here, an AMP connector drives power to an MOTM buss board.

MOTM Bench Supply

Here, the AMP connector is used as an MOTM power supply.

Because the most common use case is to wire the power supply directly to a Eurorack Buss Board, the Power Supply kit does not include a 10 pin connector or an AMP connector.

Planning

mA, or milliamps, are the common form of amperage, which is the amount of work that can be done at a given voltage. The AI Synthesis Eurorack Power Supply is a +/- 12V, 1 Amp power supply when powered from the appropriate wall wart. This means that it can support up to 1000mA of work at +/-12V.

That means that you have to plan your system to take up around 750-800mA of amperage from both the positive and negative rail in total. Here is the spreadsheet I use to plan my power and ensure that I am in good operating shape. Feel free to make a copy for your own use. What happens when you overdraw the amperage? in the best case, one or modules will simply not work because they are starved of power. In the worst case…. fire (that would be very extreme though, you would have to be drawing so much heat that it caused components to combust). I use three power supplies in my live rack, one for oscillators, one for Euro, and one for a mix of Euro and 5U.

Things to Look Out For

While most people focus on the amperage of their system, another important thing to understand and take into account is tolerance of the components. The Voltage Regulators (LM7812 and 7912) are rated for up to an one amp, or 1000mA. This is why I never suggest using a Wall Wart greater than an amp. Additionally, you want to make sure the Capacitors can handle the Voltage. If your caps are rated for 24V (or 25V as in the Wall Wart Power Supply Kit), ensure that the wall wart supply is 12V at most. You can find the capacitance voltage on the side of the capacitors:

I will update this post shortly with more information regarding how to mod the Eurorack Power Supply to provide 5V and to use an on/off switch.

Eurorack Power Guide