Marv's Blog

Volca Modular Banana Mod

Published: January 29, 2026

Originally published in 2021

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I started finding a layout that I like using Blender.

I then ended up with something that’s pretty close to the final layout.

Before starting to build, I needed to make sure that everything I had planned actually works in practice. The keyboard uses capacitive sensing and I wanted to use thumbscrews. I tried booting the volca with a screwdriver on one pad. Touching the screwdriver now correctly triggered the key (even though you could hover a bit over it since some of the accuracy was lost).

My plan was to strip all jacks and potentiometers from the PCB. The potentiometers’ solder points are quite big and easy to find.
My plan was to strip all jacks and potentiometers from the PCB. The potentiometers’ solder points are quite big and easy to find.
The jacks’ solder points are a bit smaller.
The jacks’ solder points are a bit smaller.
I started prototyping with a thin MDF board and some DIY cables.
I started prototyping with a thin MDF board and some DIY cables.

I used a compass to draw the jack and knob locations, pretty much eyeballing it just to see if the layout makes sense.

Some random knobs for visualization.
Some random knobs for visualization.
Testing if cables are in the way (a bit but the knobs can still be reached well enough).
Testing if cables are in the way (a bit but the knobs can still be reached well enough).
Bottom with most jacks installed.
Bottom with most jacks installed.
Side view
Side view

It was probably both the worst and best decision to go with olive wood. It smells and looks nice but it’s really dense and hard to work with. I also don’t have the right tools to work with harder woods (but that didn’t stop me).

One of the thumbscrews I’m going to use.
One of the thumbscrews I’m going to use.
Checking were to put the PCBs.
Checking were to put the PCBs.

The wood was really rough so sanding took a long time. In the end it still had some lines but I thought it was good enough.

I drew the exact layout on paper.
I drew the exact layout on paper.
When I was sure about the layout, I started drilling holes for the jacks.
When I was sure about the layout, I started drilling holes for the jacks.

I took apart a LAN cable and used it to connect all points on the PCB to the potentiometers and jacks.

It kept getting harder and harder as the board was getting more and more attached to the case by the wires.

The final wiring. You can see the MIDI board in the top right.
The final wiring. You can see the MIDI board in the top right.

I closed off the bottom with an oiled piece of plywood

From left to right:

  • audio out
  • sync out
  • sync in
  • CV in
  • CV in (banana)
  • CV in (banana)
  • MIDI in
  • MIDI out
  • DC

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