DIY MIDI Thru Box, Version 2

I’m planning to release a PCB and, potentially, a full kit for this project in 2018. It’d be a great help to me if you’d spare the time to tell me whether this would be of interest to you (there’s a form at the bottom of the article).

I needed an extra MIDI Thru box so I dusted off the project that I’d previously done. However, I decided I wanted to re-box it, so that it would be more in keeping with the gear I’m making now. I also removed a few frills along the way (bye, LEDs and power switch!), rationalised the board design and made the whole thing about 40% smaller as a result. Essentially, though, this is a cosmetic facelift – it’s still the same circuit design inside.



Build Documents

Schematic (Board)

MIDI THRU v2 Schematic Board

Schematic (Panel)

MIDI THRU v2 Schematic Panel

Stripboard layout

MIDI THRU v2 Board

Stripboard layout (flipped)

MIDI THRU v2 Board Flipped


My panel design and cutting guide are available below as 600dpi PDF files.

MIDI THRU v2 Panel

MIDI THRU v2 Cutting Guide

Interested in building this project?

I’m in the process of designing and procuring PCBs for this project; if you’d be interested in buying a PCB or a full kit of parts please let me know using the form below – it will help me to gauge what level to pitch the initial release at, what format to design for, etc.


5 Comments Add yours

  1. Kripies says:

    hi! first of all, thanks for sharing your projects!
    I want to make a midi thru box, but I’m a bit confused as to the optocoupler used. in the “good” appears the 6n137, but in the schematic appears 6n136. I realized that in other projects you used both.
    Which do you recommend to use for this project ?? 6n136 or 6n137 ??


    1. Morocco Dave says:

      I started off using 6N136 but I find 6N137 easier to source locally. For the purposes of this project they’re interchangeable – you can use whichever you find easier or cheaper to get hold of. Good luck with your build!


      1. Kripies says:

        ok. Finally I will try 6N138


  2. Lukas Jurk says:

    Hey, big thanks for your great tutorial. I have successfully build it. But how can i extend the number of midi-out ports. My Idea is to take another 74hc14n. pin 7 to ground, 14 to 5 v and connect pin 1 with pin 2 from the first hex-inverter and then do the same like with the first. Would it work?


    1. Morocco Dave says:

      Hi Lukas,
      Yes, that should certainly work. The other alternative would be to just build a second thru box and just daisy-chain them. Good luck!


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