Next Project: Korg R3 Aftertouch Hack

Not there yet, but it’s in reach: An Aftertouch, e.g. channel pressure control, retrofit for the Korg R3 synth.

Korg R3 under press


I really like the Korg R3. No, there’s more: I bought it second-hand out of very rational considerations, and ‘ve come to love it deeply. There are people who don’t like it for its plastic housing, for the limitations in comparison with its more expensive sibling, the Korg Radias, others hate it simply for not being a first-generation Microkorg. In my experience, it’s an excellent virtual analog synth capable of doing massive bass as well as very unusual pads. It’s versatile, it’s compact, it’s cheap, and it sounds great. And unlike the Microkorg, it’s got a proper keyboard, albeit without aftertouch.

For some reason, the MIDI Thru jack in my R3 stopped working today, which is bothersome, but also a welcome excuse to open the R3’s housing and take a look inside. I had this idea of equipping it with an aftertouch sensor for even more variation and liveliness in playing. And now I’m confident it would work, although I won’t be able to do the mod for some time. 

The basic idea was to take a couple of standard pressure sensors like the FSR-400 (have a look at the lovely Adafruit tutorial for this kind of sensors), and connect it using the R3’s pedal input. This input is supposed to be used for standard expression pedals, but of course you can use it as a generic analog input – the R3’s firmware allows you to route the control to almost any MIDI CC. There’s also some limited calibration to adapt the synth to different kinds of input.

The expression pedal jack has these signals on a standard 6.3mm plug:

  • Tip: +3.3V
  • Ring: CV In (in an expression pedal, this would be the connection to the output of the potentiometer
  • Base: GND

My first idea was to put the sensors under the synth’s rubber feet – any pressure applied to the keyboard can be measured here, after all – but this wouldn’t work if the synth rest on a keyboard stand rather than on a table. And it would be much more elegant to put the circuitry into the housing.

Anyway: here is a couple of photos from the  with notes how it might be done.



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3 thoughts on “Next Project: Korg R3 Aftertouch Hack

  1. Great idea! Did you ever get it to work? Have had the exact same experience of the R3 you had. Love this little thing a whole lot more than the microkorg :) Very interested in weither aftertouch can be applied or not!

    • Hi Troels, thanks for the thumbs-up! I must admit that this is one of the many projects that I started but never quite finished – and two months ago, the R3 had to go when I bought my Waldorf Blofeld – but I sold it to a band mate so it’s still in the family :)

      I’ve got a suggestion for you – to try an extremely low-tech approach: Buy two circular PSR-400 pressure sensors – they are about 8 € a piece – solder them in parallel, equip them with a trim pot and a 6.3mm plug, put them underneath the R3’s feet, plug the thing in – and have a look whether you can get something musically sensible out of that setup. If yes – we know where to put them, don’t we? :)

      (Please: if you do, keep me in on your experiences.)

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