This voltage-controlled oscillator is based on the Curtis CEM3340 VCO IC. It's an easy kit to build, or you can get it pre-assembled.

Features
* Square, triangle, and sawtooth waves
* Coarse and fine-tuning controls
* Adjustable 1V/O CV input
* Mod, PW and hard-sync inputs
* Reverse-polarity protected
* Eurorack-style power input

Inputs
* 1V/O CV
* Mod CV (AC-coupled)
* PW (Adjusts duty-cycle of square wave up or down)
* Hard-sync

Outputs
* Square / pulse wave
* Triangle wave
* Sawtooth wave

Controls
* Coarse tune
* Fine tune