Foot Switchable iPhone Controller

This was a continuation of an idea from a very old post. I created a foot-switchable iPod controller for myself that incorporated a DI for easy sample playing on stage. A lot of people really liked it. One such person was Justin who plays in the band Ulthar and Veil. He asked me to cobble a simple version together for him, so I did.

I call it an “iPhone controller” now because who the fuck uses an iPod these days. Do they even make them anymore? I have mine, but… well whatever, the function of the circuit accomplishes the same goal: one stomp makes it play/pause, two stomps makes it go forward, three stomps makes it go back. For fuller details on how to build one, check out the details of the old post. To see the guts of this simpler version, read on.

I actually used the same DI enclosure leftover from my old build to put this together (never throw anything away). It’s simpler than mine, but it works. Justin plays drums, so I opted to have a cable system instead of having the iPhone be inside a larger enclosure. That way, he could mount the iPhone (or iPad, even) on his drums and see what it was doing while the foot switch was at his feet.

Instead of ripping apart an old TRRS cable, I was able to buy one online from some “maker” website. Not super easy to find, but it was impossible seven years ago. It was much easier to work with than the one I repurposed from old headphones. I soldered the cable to a 4-pin XLR plug and loaded the 4-pin female end to where the old XLR jack was. I got the 4-pin plug and jack from a weird electronics shop somewhere while on tour in Florida years ago… I have no idea how readily available they are online.

I used the plugs leftover from the old DI to create left and right outputs. These need to be plugged into a stereo DI to be played over the PA. It’s just barely enough signal, but it needs a lot of gain. Justin was supposed to give it back to me so I could add a boosting circuit, but I guess it works well enough that he never bothered.

It’s hard to see, but there is a ground wire connecting the two outputs. I put a 1kΩ resistor directly on the foot switch that connects the ground and the mic of the TRRS cable. The switch connects them directly when you stomp and that tells the iPhone what to do.

A cool thing about this stereo set-up is the potential to send different audio signals to the left and right outputs from your iPhone or otherwise compatible mp3 player. One could be samples, the other a click track. Or you can have a sound guy do some weird panning shit. I dunno, the possibilities are near endless (and by near I mean two… there’s two possibilities).

So that’s it. Not much in the way of a tutorial, but the old post from seven years ago covers it pretty well. Maybe this’ll give people some new ideas? Get crafty!

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