Jennings J7 Univox Analog Tube Synthesizer

The instrument

Developed by the Jennings Organ Company, West Hill, Dartford in the UK, the Univox was a monophonic, portable instrument with a piano top, similar to the claviolin. Tom Jennings found a local electronics engineer who studied the claviolin and designed a different circuit to the existing French patent. After initial shortcomings, the Univox was marketed on a large scale in 1951/1952. The first version was the J6, a model with one keyboard, later followed by models with two rows of tone and effect controls. All models were supplied with screw-on metal brackets to mount them under the right side of a piano. Most customers were pub owners or pianists who performed in pubs.


The sound of the Univox came from a vacuum-tube sawtooth generator which in turn was modulated by a diode waveform shaper circuit. The pitch range was extended to three octaves (five in later models) using a frequency division technique which also allowed the playing of multiple octaves of the same note from one key. The instrument was controlled by a three octave F to F miniature wooden keyboard and came with it’s own 6 watt amplifier and 8″ speaker all built into a leather carrying case;
The Univox keyboard had a double contact system under the key allowed basic control over the note shape – striking the key harder caused a thyratron impulse generator make a shorter decay, creating a staccato effect, striking the key softly gave a long decay of up to two seconds. A vibrato oscillator was also provided to modulate the output and also to retrigger the thyratron tube to create ‘mandolin’ type repeated notes. The Univox’s front panel consisted of fifteen switches to further control the timbre of the instrument, three vibrato controls, a thryratron modulation control and an overall knee operated volume control. (Source: 120 years)