OB-X Voice + Controller Board DIY Synth


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*Now Shipping!*

Thanks for checking out Rosen Sound’s first DIY synth project! This project is based on our popular replacement Oberheim OB-X voice cards, which are 1:1 clones of the originals. We have now designed and produced controller boards for those cards so they can be used as a single voice synth!


  • DIY! Nothing will give you the feeling of gratification quite like building your own synth!
  • All parts are available by simple means. No hunting down expensive obsolete transistors! Yes, some parts will not be obtainable on Mouser, but we tell you exactly where to get em!
  • 2 beefy analog VCO’s (Saw/Pulse)
  • External inputs for audio, PWM, and filter FM via 3.5mm jacks
  • The beefiest LPF ever put into a synth voice. The OB-X has a SEM like LPF that is revered.
  • If you’re a tech, these can be used to test OB-X cards outside the OB-X, reducing repeated mechanical stress to the original mother boards

Build difficulty: Easy! Definitely beginner friendly, and you’re sure to learn a thing or two about building with discreet thru-hole parts.

Projected cost: At this time, the total expected BOM hovers around $130-200. The mouser cart alone is $100, and the other bits can vary, and there are many sources. The wide range is also accounting for the power supply. See notes below.


  • The boards and circuits are confirmed to be working in Rev 1.0 that is now shipping. All cuts and some jumpers are made before shipping. Once you solder in 6 resistors, some small jumpers are needed.
  • There is currently no case available for this project, but we might do that in the future
  • A PSU is in development now that will be provided at cost once available (will be available by end of June). The voltage requirements is +/- 19VDC.

What’s included:

  • 1x OB-X voice card
  • 1x Controller card for the OB-X voice card
  • BOM with links
  • Mouser cart for most components
  • Parts placement sheet
  • Build and calibration directions

Additional information


DIY, Pre-Built


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