A simple tealight is all that’s needed to “fire up” the Candela Vibrophase tremolo pedal from Zvex (zvex.com). How does it work? Two solar cells take electrical power from the tealight, and a Stirling engine, a 200-year old design, provides mechanical motion powered by the candle’s heat. The Stirling engine uses a hot cylinder, a cooling cylinder, and the expansion and contraction of hot air to drive a flywheel, which drives an optical disc. The oscillations of the optical disc interrupt the light from the candle going to the photocells of the phaser/vibrato circuit. You control the speed of the Stirling engine—and thus the effect—by moving a spherical neodymium magnet closer or further away, and that creates an electro-magnetic force that fights against the magnet and slows down when you get close.
At $6,000, the Candela Vibrophase was meant to be an inspirational, one-of-a-kind piece; this clever bit of boutique engineering from Zachary Vex takes about 77 hours to make, according to Reverb.com, where you can find all of Zvex’s cool hand-painted effects pedals.