The circuitbenders Harmonic Engine PCB is a clone of the E&MM Harmonic Generator. This was a project by Paul Williams, published in Electronics & Music Maker magazine way back in 1981.The circuit uses a 4046 Phased Locked Loop (PLL) to track an input signal and generate a squarewave output at harmonic intervals to the frequency of the input. The squarewave can be set to +/- three octaves, and can also produce 3rd or 5th harmonies. That's the theory anyway. In practice, the note tracking only works really reliably if you use very basic waveforms at the input. If you use anything else, then everything very quickly descends into a beautiful kind of chaos, with all kinds of bizarre gurgling digital squeaks and squeals vomiting forth. It's especially effective with percussion sounds, converting each hit into some kind of warped electronic splatter.

This is just the bare unpopulated PCB. We do not supply kits for the full build, There's nothing rare or very difficult to get hold of in this build, although the 4526 4-bit binary counter IC appears to be one of those little used 4000 series CMOS chips that aren't stocked by many component suppliers. There's no setup or calibration involved, and there's nothing complex to go wrong, so as long as you are careful with your soldering there's no reason why this shouldn't be a beginners project. The PCB has board mounted pots at the front and a eurorack power connector at the back, so it could easily be used as a modular synth module, although you may have to attenuate levels on the way in and boost on the way out. Theres no reason that you couldn't use it as a stand alone effect in a desktop case, or wire the pots to the board so you could use it as a guitar pedal.

You can download the build guide and parts list from HERE.

You can find a couple of demo videos of this board in action on YouTube HERE and HERE.

The board will run on a 9v battery or a 12v power supply, but check out the build guide for power options.