Category Archives: Eurorack Power Buses

Eurorack Power Bus – Update 1.1


The Eurorack Power Bus with its 14 Euro connectors is back in an updated version.

The version 1.1 slightly simplifies the BOM and adds a second power input terminal, either for chaining to a second bus or to ease the installation as PSU cables can be wired either from the bottom or from the top of the case.

The Eurorack Power Bus board is a convenient way to distribute the required power voltages across a small-to-medium Eurorack system.

There are 14 Eurorack connectors so up to 14 modules can be powered at once. Two additional 16-pin DIL connectors are dedicated to Analogue Systems compatible modules. Plus, six 3-pin connectors are present for your powered 1U modules.

The bus can be equipped with a onboard +5V linear regulator.

The 3 LEDs let you know if the 3 power rail voltages are present. The form factor of the bus is 20cm long, 5cm wide. The short distance between the connectors ensures lower voltage drops under high current consumption.

Building the Eurorack Power Bus

The build process is simple:
Start by soldering the three resistors. The resistors are not polarized. R1 and R2 are 1k Ohms (Brown, Black, Red, Gold). R3 is 470 Ohms (Yellow, Violet, Brown, Gold).
See Resistor color code chart.

If you use the onboard +5V regulator, add now the two 1N4007 diodes. They are polarized. Follow the white band marking on both silkscreen and the diode case. The white band shows the Cathode side of the diodes.

Bend the leads of the +5V regulator U1 (7805) at 90°, according to the silkscreen.
You can either bolt the regulator to the PCB or solder the metallic tab to the square pad. Soldering the tab requires to apply enough heat to both the PCB and the regulator heat sink. The solder must flow under the metallic tab to effectively bond the regulator to the PCB.

+5V Regulator and its required components

If you intend to use Analogue Systems compatible modules, you can solder in place the two 16-pin DIL sockets. If not, you can simply skip this step.
The DIL socket is polarized: align the notch to the silkscreen marking.

If you intend to use the 1U connectors, you can nw solder the six 3-pin connectors. If not, you can simply skip this step. Those connectors may require some adjustment to be correctly aligned vertically. Try to solder one pin at a time and then adjust the position.

Eurorack Power Bus V1.1 – Top side
Eurorack Power Bus V1.1 – Bottom side

Interactive BOM (bus_eurorack-1.1-ibom-2019-01-17)

As usual, you can find the Eurorack Power Bus PCB on Tindie.

Eurorack Compact Power Bus – version 1.1b B(L)ACK in stock

The BLACK solder mask is awsome!

New revision for the Eurorack Compact Power Bus!

The Compact bus is one of the smallest yet powerful Euro bus in the world. Yes really 🙂 It’s only 10cm long but you can plug 8 modules plus 4 tiles and one Analogue Systems module!

Modulaire Maritime cases are equipped with the Compact Bus!

Available now on Tindie!

Construction details

The board is really easy to solder. There are, on the bottom side of the board, 3 SMT resistors and 3 SMT capacitors. But don’t be afraid, those are 1206!

1206 SMT devices are big enough to be soldered with standard through-hole equipment. I personally use a cheap soldering iron.

What makes the difference is the thickness of your solder. I recommend 0.5mm solder wire. 0.3mm is better, but consider it only if you plan to do a lot of SMT soldering in the future.

Besides, it can be a great opportunity to experiment your first SMT soldering job. And don’t worry, if you aren’t successful, well, your board will still be fully functional! Only the LEDs might be inoperative.

Step by step assembly

Start by soldering the 6 SMT devices. Apply a small amount of solder on one pad of each component. with fine tweezers, place your component in its designated location, then reflow the solder with your iron while you slightly adjust the alignment of the component over the pads.
If you’re satisfied with the position, you just have to solder the second pad, and voilà!

If you do own an Analogue Systems module, you can solder the 16-pin DIP connector now. If you don’t have such module, skip this step.

Solder the 8 Eurorack connectors. I recommend boxed headers but some will prefer the unboxed ones. It’s your call! Eurorack Connectors are 2×8 pins, 2.54mm pitch.

Next, you can solder the four 3-pin “1U Tiles” connectors. Again, if you don’t use 1U Tiles, then simply skip this step.

I recommend to solder the LEDs now, before the big power input connector. If you flip your board, it will sit flat on your desk. It should be easier to align the LEDs vertically.

Last step is the power input connector. You can use different solutions but the one I use and recommend is the Screw Terminal Block. It allows you to accommodate a lot of different power sources. The pin pitch is 5.08mm.

Power on

The board requires 4 power rails: +12, -12, +5 and 0V (0V is marked “GND” on the board). The +5V rail can be skipped if your modules don’t require it.

If you have some doubts about the difference between the -12V and the 0V, please read my previous post “Ground is Not your Negative Rail“.

When powered on, the LEDs should lit. If not, double check your solders and most important, check the polarities of both LEDs and your rails.

Documentation