MIDI Thru box

1-to-8 (or more) output MIDI Thru utility box, which lets you connect multiple instruments to one MIDI source in a star configuration.

I got tired of figuring out MIDI-thru configurations with my external gear, so I decided to connect them in a star-configuration: MIDI coming in from one cable, then from there to all instruments.

There are plenty of such boxes out there, but they all seem just a bit more expensive than I’d like. Given that’s it’s a simple circuit and I already had all the hardware, I decided to design my own.

The board can be expanded by connecting to one a second unit. With the help of a jumper, it can become a 1-to-16 or more box (with further boards chained). Alternatively, two boards can share only power, making for two disctinct 1-to-8 MIDI Thrus powered from one supply.

I wanted anyone to be able to replicate this project, so I’ve documentated the entire process of building one and made all the manufacturing files available. The project and all relevant files can be found on GitHub, under my fiancĂ©e’s and my “Reflex Creations” brand: ReflexCreations: multi-midi

Work Involved

  • Circuit design (starting from MIDI electrical spec) + breadboard prototyping
  • Schematic capture (KiCad)
  • PCB design (KiCad)
  • Enclosure design for 3D printing (FreeCAD)
  • Some 3D modeling of PCB-mount parts, for a complete PCB 3D model (FreeCAD)
  • Documentation

Additional Images

The populated PCB:

Exploded view of the 3D model: