Congratulations! You’re a few simple steps away from owning a great little music-tech gadget that will serve you for years and that you’ll have the satisfaction of having built yourself.
Building this project takes about half an hour if you’ve done some DIY electronics before, complete beginners should expect to take a little longer. The instructions assume that you can identify components, solder and do simple voltage and continuity tests with a multi-meter. There are lots of resources available to help you learn these skills – just hit Google or YouTube and you’ll soon be ready to start!
But before you do… we highly recommend that you
- Take the time to read through this guide a couple of times
- Check your parts against the Bill of Materials at the bottom of this page to ensure that you have everything that you need
Enjoy building your MiniBus, we hope you make great music with it!
Tools
To complete this build you will need
- Soldering iron
- Solder
- Wire cutters
- A voltmeter or multimeter
You’ll also need a clean, well-lit workspace with a heat-resistant surface to work on.
Build Instructions
Putting MiniBus together is very simple, as there are few parts and only two types of part.
All components go on one side of the PCB – the side with the part numbers printed on it.
Solder parts into the marked positions; where a part has to go a specific way round there will be markings on the PCB to guide you, and a clear note in the instructions.
We add parts to the board in height order, starting with the shortest parts (this makes the PCB easier to manage and handle during the build).
J1 to J4 – 4-pin headers
You’ll find one of these in the middle of each edge of the PCB. Working with one at a time, locate the pin header in the holes, flip the PCB over and solder into place.
You might find it useful to just solder one pin, then check that the header is straight, making any adjustments before soldering the remaining 3 pins.
J5 to J14 – box headers
The ten Eurorack power headers have to be correctly oriented in order to function correctly and not damage your modules, so take great care to ensure that the gap in the header shroud matches the gap in the printed outline on the PCB silkscreen.
Position all of the headers, then lay a piece of thin card over them to help you to hold them in place while you flip the board over. Slip the card out from under the headers then solder one pin of each header into place.
Before you continue to solder the remaining pins, flip back over and check once more that all of the headers are correctly oriented.
If you are happy that everything is laid out correctly, continue to solder all of the remaining pins.
That’s all there is to it – your MiniBus is now ready to test and use.
Testing
Before we connect the MiniBus to a power supply, we’ll make a quick test for short-circuits. You’ll need your multi-meter for this step.
With your meter set to detect continuity
Pick any one of the edge pin headers J1 to J4. Using your meter, ensure that there is NO continuity between the four pins.
Next, choose one of the 16-pin IDC headers and ensure that there is NO continuity between any two pairs of pins. J5 or J10 are good candidates for this test, as they have the pin designations printed clearly below them.
If your MiniBus passes this test, it’s safe to connect it to your power supply and continue with the next set of tests. If it fails this test, take a good look over the back of your PCB for shorts between soldered connections. Rectify and try again.
With your meter set to measure voltage
Connect your MiniBus to your modular power supply by connecting the supply to one of the 16-pin IDC headers. Select one of the edge pin headers J1 to J4 to measure. Touch your meters BLACK probe to pin 3 (GND).
Touch the RED probe to pin 1 (+5V). You should measure approximately 5V here (a small amount of drift is acceptable). If your power supply does not provide a 5V rail, you should measure 0V here.
Next, touch the RED probe to pin 2 (+12V). You should measure approximately 12V here (a small amount of drift is acceptable).
Finally, touch the RED probe to pin 4 (-12V). You should measure approximately -12V here (a small amount of drift is acceptable).
Repeat these tests on one of the 16-pin IDC headers. J5 or J10 are good candidates for this test, as they have the pin designations printed clearly below them.
IMPORTANT NOTE: These tests are designed to ensure that MiniBus
- is safe to use
- will not damage your power supply
- will not damage your Eurorack modules
Skipping these tests, carrying them out improperly or ignoring the results can carry serious risks and consequences for you and your equipment. In proceeding to connect MiniBus to your equipment, you are assuming liability for any consequential loss or damage.
Using MiniBus
To get power into your MiniBus, you can simply connect your Eurorack PSU to one of the 16-pin headers. Alternatively, you can use one of the edge pin headers (J1 to J4) to accept power into your MiniBus (this might require you to obtain or make a cable specifically for this task, though).
There are two ways of joining MiniBus boards together, each has advantages and disadvantages.
Join at the edges
You can join two boards together simply by connecting adjacent edge connectors together. The advantage of this approach is that you do not sacrifice any Eurorack power headers and each board will now behave as an independent CV/gate bus (advantageous in some ways). On the downside, each board will now behave as an independent CV/gate bus, which not everyone will want!
Join with ribbon cable
Alternatively, you can use a 16-way ribbon cable to join two boards. Both boards will now be part of the same CV/gate bus – but, on the downside, you’ll have two fewer connections for Eurorack modules.
Choose the method of connecting boards that suits you best. Remember that for any “chain” of boards, you must only put power in from your power supply once.
Bill of Materials
In addition to your PCB, you’ll need parts. The full list of parts for the project is given below, with Mouser part numbers to aid you in identifying compatible parts. Although we’ve used all Mouser parts in the example build above, you may be able to obtain cheaper compatible parts by shopping around.
| Reference | Value | Description | Qty | Mouser Part | Notes |
|---|---|---|---|---|---|
| J1, J2, J3, J4 | 4-pin, male | IDC header | 4 | 855-M20-9990445 | |
| J5, J6, J7, J8, J9, J10, J11, J12, J13, J14 | 0.1uF | Shrouded IDC header | 10 | 538-70246-1601 |
Make Synths Not War 