It’s alive!!! Korg Monotron + DIY sequencer

I’ve been wanting to build a sequencer for a long, long time.  Once I saw the Korg Monotron, I knew it would be a perfect complement to a homegrown Baby 10 variant.  Still a beginner when it comes to circuitry, I figured I’d build a simple 4-step version to insure I could get it functioning correctly and perhaps later expand on it or build a bigger one.

A very tight squeeze inside the casing, but just enough room for an 1/8″ jack.

In opening up the Monotron, the labels for pitch, cutoff, gate, ground, etc. are clearly marked, and the mod and DIY community has done amazing things thanks to Korg’s willingness to share the schematic and present everything so accessibly.  I was planning on tapping into the pitch point on the board following the excellent work done at the Din Sync blog, as the main thing I’m interested in is being able to program melodic content on the Monotron rather than rely on the ribbon controller for input.  In my mind, this would elevate the unit beyond being a super fun toy, and into the realm of “serious” music making.  Some quick tests yielded less than favorable results in connecting the 4-step sequencer to the pitch and ground contacts, and I tried the gate point instead.  Surprisingly, this proved to be exactly what I was hoping for.  I’m sure more enterprising and better educated hackers, musicians, and electrical engineers could explain in more detail what was going on, but I held on to Rule #17 from Nicolas Collins’ Handmade Electronic Music:  “If it sounds good and doesn’t smoke, don’t worry if you don’t understand it.”  😀

So, if you’re trying to mod the Monotron simply to have pitch control via an external sequencer and don’t want to use something like Silent Way by Expert Sleepers to calibrate the dodgy pitch tracking, you may try tapping directly to the gate contact and bypassing the pitch contact altogether.  Worked for me.  Now, let’s just hope it doesn’t blow up.  😉

The sequencer itself features 4 pots for pitch control, 4 toggles for on/off selection of each step, a switch each for reset and pause, and a toggle to go from 4 steps to 3 to have the ability to switch to triple meter.  And of course, blue lights.  Runs off a 9v battery and not having to calibrate pitch with software plugins means I’m not tied to my computer, and really, who wants to do that when playing with something as mobile as the Monotron?

Anyone looking for more technical information regarding hacking the Monotron should definitely check out this thread.  Some great material here from people doing very interesting mods.

I’m including the crappy hand-drawn schematic (which probably has errors) and the parts list for the sequencer I built in case anyone wants to try making one.  It’s only the 2nd schematic I’ve ever drawn, so bear with me.  And if anyone has any suggestions for cheap/free software for the Mac to design schematics, let me know!

Messy, I know. Errors? Probably. Use at your own risk. 😉
Most of the parts are from Jameco. A few from Radio Shack. Easily obtainable.