Sometime time ago I challenged myself to build a very small synthesizer: the result was this microsynth. It is based upon 40106 square wave oscillators. Two oscillators are present. One modulates the other through a pulse shaper circuit. The output is 1/8" mono. Power is supplied by the same connector used for guitar pedals.

TuneFrequency of the main oscillator
GateFrequency modulation oscillator
ModulateAmount of modulating oscillator to apply to the main oscillator
WidthPulse width of the modulating oscillator
VolumeOutput volume


A large part of this project was an exercise in creating reproducible devices. From the PCB layout to the case design, each step was performed with this in mind. The layout for the PCBs was done in Eagle. They were then created using OSH Park. The case is made from laser cut plexiglass. Components are sourced from a single supplier, Mouser.


Two prototypes were created before the design was finalized. Here they are above the completed device.

The large black box was created first. It contains the original circuit built on perfboard. At the time, MPF102 JFET transistors were not obsolete and were used in this circuit. They have since been replaced with J113 transistors. The second prototype was created to test the layout. The final design allows for a case and uses shorter components.