HOW TO – SX-150 button mod

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. Michael Una says:

    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. John Paulson says:

    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. Collin Cunningham says:

    @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. Anonymous says:

    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. Collin Cunningham says:

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

  6. Victor says:

    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.

  7. David Stretch says:

    Nice one, I just got one of these for Christmas and the first thing I wanted to do was switch the stylus for buttons!  That’s my project for the new year sorted :)


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