Adding an Expression Port to your Midistomp Six

Published by Simon G on

The defeaning roar of the masses has been heard! Midistomp six can now have an expression port (or two!) and you can do it easily and extremely cheaply at home!

You need a TRS jack like this, this, or this.
You need a soldering iron and solder
You need three wires between 8 and 10cm long (no longer – they will pick up too much noise)
You need a drill and a drill bit the size of the TRS jack’s thread
And you’ll need a phillips head screwdriver

Step 1.
Open up the midistomp six

Open the midistomp with a screwdriver

Step 2.
Place a bit of tape inbetween the middle switch’s plastic housing and the USB cable inside the midistomp, then extend the piece of tape over the edge – this will mark your “window of opportunity” on the outside of the midistomp so you can drill the hole in the correct place. Then just drill in the middle of the piece of tape and a bit further away from the bottom than the middle (to make sure you miss the circuit board. Treat the circuit board and the bottom, not the bottom edge of the metal enclosure)
now drill the hole. Drill full-speed, but don’t press hard because you risk push a large amount of the drill bit into the enclosure and potentially hitting something vital. If you’re careful, you can’t possibly hit anything.

make sure you blow out the enclosure after drilling. You don’t want a small speck of aluminium causing a short circuit somewhere!

Step 3.
Solder the 3 wires onto the TRS jack. TRS stands for Tip, Ring and Sleeve. For an expression pedal, the red wire goes to the Tip, the black wire goes to the sleeve, and I like to use a different color for the ring, which is the “wiper” or “data” wire.
some brands of expression pedal switch some of the TRS contacts around so make sure you double check your pedal before you wire this up.

Step 4. insert the jack into the hole and tighten the nut on the outside. Make sure the wires are in a good position and easily accessible from the open bottom of the enclosure.

Step 5. solder the wires to the pins of the processor as shown in the photos. The power and data (tip and ring) wires are at opposite ends of one long side, and the ground (sleeve) is on the adjacent corner to the power (tip). Please make sure to note the orientation of your device compared to the photo before soldering.

If you are also adding a second expression port, solder the second data wire to the pin directly next to the first one on the long side (Notes on the photo). The power and ground can be piggybacked off the same pins as the first expression port.

Lastly, download the expression profiles from the downloads page, and upload your desired profile! Plug-n-play baby!

1 Comment

Adding TRS MIDI to your Midistomp Six - midistomp · May 26, 2020 at 12:15 pm

[…] To begin this tutorial, you will first need at least one expression port on your midistomp six. If you do not have one, you can install one (or two! – much more flexible!) with this tutorial. […]

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