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