The JamMan Solo XT by Digitech is a basic, compact, affordable looper pedal. It does most everything I would need, but after using it a few months, I found the lack of a dedicated stop button really frustrating. Sure, you can stop a loop by quickly double-tapping, but this is actually not very easy to do in the heat of the moment, especially when you’re juggling all the other things you need to remember in this one-pedal setup (long-press is undo, tap once is overdub/start track/start record).
To add a stop button as well as loop advance, you can add an extension pedal that they sell (the FS3X), but it’s a bit bulky for my liking. The connector is a standard Stereo TRS (tip ring sleeve) 1/4 jack, so I guessed that it worked by just momentarily connecting (or “shorting”) either ring or tip to ground (sleeve). For the 3rd button function, it’s probably shorting both simultaneously.
I plugged a spare broken headphone cable in with some bare wires and experimented with touching them together in different combinations until I found the pair of wires that executed the stop function. Then just soldered it to a super-cheap momentary switch button I had in my electronics box. I secured the connection with this clay-like compound called Sugru. This stuff is great because it hardens to a stiff rubber-like material and is very durable.
Finally, I stuck the button on top of the pedal with some poster putty. It holds pretty well, but I may glue it down if I need some more durability. But as is, it’s completely removable and doesn’t modify the unit in any way.
If I really wanted to get a permanent solution in there, I’d probably drill a hole in the top of the housing and wire the button directly to the connector’s pads on the circuit board.