The Univibe is actually a footpedal-operated phaser or phase shifter for generating chorus and vibrato simulations for electric organ or guitar. It was introduced in the 1960s by Shin-ei, and was intended to emulate the “Doppler sound” of a Leslie speaker. Although not a really successful Leslie-simulator, the Univibe has turn out to be an effect in its own right, putting its stamp on tracks like Robin Trower’s “Bridge of Sighs”, Jimi Hendrix’s “Machine Gun” and Pink Floyd’s “Breathe”. The effect, though generally associated with chorus, is actually produced through a staggered series of phasing filters, unlike the commonly aligned filters of a regular phasing effect. Not like most other phaser pedals, this is achieved without having the use of op-amps.
The UniVibe is well-known from Jimi”s use of it. The LFO is actually a phase shift oscillator, using the dual 250K pots inside the pedal assembly to control speed. A contemporary version would substitute an LED/photocell optocoupler for the four LDR”s and also the incandescent light bulb that makes the shifting function. This IS just a 4 stage phaser, possibly with some distortion from the signal path thrown in. Considering that the Univibe (r) is getting reissued by Dunlop, Dunlop most likely owns the “Univibe” trademark nowadays. This schematic bears no resemblance, except accidental, to the reissue that Dunlop or any person else might be developing.
Download UniVibe Pedal for Electric Organ/Guitar Schematic in PDF File: