Vox Boosters - Jennings Musical Industries (JMI).
Below, a collection of documents and parts of documents relating to Vox boosters - treble, bass, distortion and mike (mic).
The first mention one finds is in late 1964 - the Treble-Booster noted in the "Precision in Sound" newspaper-format catalogue.
Work on the other three units - bass, distortion and mike - probably designed by Denney (in conjunction with Les Hills?) took place in 1965.
Thomas Organ began advertising three of the set of four (the mike booster was omitted) in late 1965. The three units were in polished chrome cases. In England, only the treble booster was sold in a plain polished case. The other three were coloured (see below, JMI catalogue from 1966).
A further distinction, useful in determining the origin of treble units (polished chrome finish in both England and the US), is that the legend "Treble-Booster" has a hyphen in England, but none in the States.
The Thomas schematics for its first-generation boosters are at the foot of this page. They are dated June 1966.
Thomas-made units were supplied in a plastic case:
A first-generation Thomas Bass Booster.
English boosters were supplied in a cardboard box along with an instruction sheet:
A JMI Treble Booster. Further pictures on this page. Note the line at the foot of the instruction sheet: "built by JENNINGS MUSICAL INDUSTRIES Ltd."
The circuit board of the JMI Treble Booster pictured above. The jack plug socket, soldered directly on, is made by RE-AN, an English company based in Dartford (Burnham Road), not far from the Vox Works at 115-119 Dartford Road.
"Practical Electronics" magazine, April 1970. An advert placed by "Re-an Products Ltd".
So far as one can tell, at least some of the first-generation boosters offered by Thomas Organ in the USA were assembled in America - either by Thomas itself or one of its contractors:
The on/off switch in a first-generation Thomas Organ Vox Distortion Booster. "UND LAB" = "Underwriters Laboratory", the certification authority in the States.
Thomas Organ Vox Distortion Booster: the same make of large black capacitor was used extensively in the Super Beatle and other US-made Vox amplifiers.
Detail from a Super Beatle circuit board.
Detail from the JMI "Precision in Sound" newspaper-format catalogue, late 1964. The Treble-Booster is mentioned but not pictured. Perhaps the format had not yet been decided upon.
The text reads: "VOX TREBLE-BOOSTER (Not Illustrated). Miniature plug-in 'overtone' unit giving a super extra 'zing' to the treble. A really worthwhile extra for the lead guitarist."
Detail from the JMI pricelist of May 1965.
The Thomas Organ (USA) Vox "King of the Beat" catalogue from late summer 1965. As above, only the Treble Booster.
During the course of 1965, Jennings developed three new boosters - bass, distortion, and mike - in advance of the The British Musical Instrument Industries Trade Fair in August 1965. They were duly exhibited.
"Beat Instrumental" magazine, October 1965 - review of the BMII Trade Fair in August of that year.
Detail from the JMI pricelist of November 1965. Note that the mike booster does not figure.
"Beat Instrumental", December 1965.
Thomas Organ pricelist of September 1965. Care is needed with the images on this page. A number are unsignalled composites.
Page from the Thomas Organ (USA) "British Sound" catalogue of early 1966. As above, the treble, bass and distortion boosters.
All four boosters pictured in the JMI catalogue of mid 1966.
Detail from the JMI pricelist of August 1966. Jennings bass, distortion and mike boosters generally have coloured cases.
A detail from the Thomas Organ catalogue of later 1966: V810, V806 and V816. The image will be replaced with a better one as soon as possible.
During the course of 1967, Thomas Organ devised a new style of booster - second generation - with an intensity control and repositioned jack plug and socket. Jennings retained the old style.
Thomas Organ catalogue, 1967, illustrating the second-generation boosters.
A Thomas Treble-Bass Booster.
JMI solid state catalogue of mid 1967.