Music Technology
HOW TO – SX-150 button mod

Sx150 Buttonmod Macro

A number of people have asked for more info on how I modded the Gakken SX-150 analog synthesizer for pushbutton usage. If you’d like to add a DIY keyboard youself, check out my recipe –

Parts – Feel free to experiment with other resistor/trimpot values and using more/less switches. The basic idea here is to divide up the resistance of the original control strip into sections which are then connected via the switches to the stylus wire.

  • 7 x pushbutton switches (I picked up some cheap ones here)
  • 7 x 4.7K resistors (I used 1% tolerance, but 5% is fine)
  • 1 x 100K trimpot
  • prototyping perfboard

Schematic –
Sx-150 Buttonmod Schem
(click for larger view)

I removed the control strip and cut a piece of ‘pad-per-hole’ perfboard about the same size – then built the keyboard circuit per the above schematic. I ran wires through the preexisting holes used for the strip and soldered them internally to the appropriate board connections. After testing it out, I secured the board in place using a bit of hot glue.

Sx150 Control Strip

I find the pushbutton/keyboard setup to be a lot more fun than the control strip, but still have that stylus hanging about. Hmm, perhaps the strip could be mounted additionally in another area … until then, you can see the finished product at work in the original video I posted –

Once you experiment a bit with your own design, you’ll likely notice how simple and versatile it can be. I picked up the basic concept a while back from Ray Wilson’s excellent Music From Outer Space. Drop a line in the comments if I’ve left anything out/etc – and most importantly, Have fun!

SX-150 Analog Synthesizer Kit

14 thoughts on “HOW TO – SX-150 button mod

  1. For Makers out there who want to tune these notes to a scale, I recommend putting potentiometers in place of the fixed resistors in Collin’s example. You can then use an external tuner to make sure each of the notes corresponds to a note in the Western musical system, for maximum intergration with other traditional instruments.

  2. No, get your mind out the gutter.

    Haha. Anyway, would it be possible to swap the resonance switch with the stylus? That might be cool. :)

  3. @Michael – great idea! – and if people use the regular resistor method, it might be a good idea to breadboard first to determine the most pleasing interval between switches

    @John – another awesome idea – not sure of the ease of implementing that, but a quick look @ the schematic should give an idea.

  4. I bought one of these from Make, built it exactly as shown in the Japanese magazine it came with, and all I got was a couple of squawks and some static, then nothing. I rechecked all the connections – is it possible I got a dud?

  5. @[blank] – sure duds are possible, but I haven’t heard of one yet. Do you have any pics of the internal wiring/etc?

  6. I have another idea guys. Why not replace the button board with a touch sensitive either pressure or contact (prefferably pressure so you can use not only afinger but a stylus aswell) and assign a variable on the vertical axis also. Just wonder if it’s possible to connect a touch sensitive pad on this device.

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