David Díaz.

DIY Midi Cable for the OP-Z and ZM-1

I’ve been using an old Rockband Keytar as a midi controller for the longest time. I usually take advantage of the OP-Z’s ability to be a MIDI host to use the keytar via a midi to usb adapter. This is fairly cumbersome as I have to use big cables and a USB-A to USB-C adapter.

Last year I got myself a ZM-1 module for the OP-Z which allows me to connect MIDI devices via a 3.5mm jack. These are fairly easy to put together and I had all the spare parts I needed hanging around already so I decided to make a couple.

All you need is a MIDI jack, and 3.5mm jack and some cable. I used a midi jack that already had it’s cable attached. I took this from a previous midi project so that cut the soldering in half.

The parts we'll need. A midi jack and a 3.5mm jack"

I couldn’t find documentation stating weather this cable is meant to be type a or b or something else. So I tried wiring it as a type-A (a being the “standard” from what I know). This didn’t work, it turns out is actually type-B. Here’s the diagram:

The diagram we'll follow, current source to tip, current
sink to the ring and shield to the sleeve "

Some soldering later and the cable is mostly ready:

The cables soldered onto the 3.5mm jack"

I used some heatshrink as strain-relief. I was also lacking the piece of plastic that screws to the 3.5mm jack so I wrapped it in some extra heatshrink to give it some strength. Here’s the final cable:

The finished cable, now with some heatshrink"

Here’s what my keytar setup looks like now:

The op-z on top of my rockband keytar"

It works flawlessly and makes for a fun little weekend project.

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