Late 1964 / early 1965: Dick Denney demonstrates on film the resonant boost effect (Mid Range Boost) built into his prototyype Guitar Organ. A video with sound exists.

October/November 1965: Dick Denney visits the Thomas Organ factory in Sepulveda, California, to advise on the pre-production American-made solid state range. A synopsis of the Thomas transistor shown to him can be found on this page. JMI, it should be said, already had "transistorised" units of its own at that point - principally, the T60 bass amplifier, and the preamp of the new 100W PA amplifiers issued developed in early 1965. For amplifier manufacturers of the time, the biggest difficulty was obtaining consistently reliable transistors for power sections.

Late 1965 / early 1966: Thomas Organ reportedly sends a solid state amplifier to the Vox Works at Erith for testing. Reception is cool.

Early 1966: the 4-series and 7-series amplifiers are designed and produced - transistor preamp, valve power amps. The Beatles receive early production (not prototype) 7120s in mid April. Rodney Angell, who worked in the JMI R&D from 1965, was clear that the design of the 7-series amps had been contracted out. The same is said, albeit elliptically, in "The Vox Story", ed. Denney and Petersen (1993), p. 61. The power sections of the range were based on existing Jennings circuits however.

Early to mid 1966: Design and prototyping of the new range of fully solid state amplifiers. Meanwhile the 4-series and 7-series amps are promoted as the "latest thing".

July 1966: JMI sends photos of a treble and bass model to the Patent Office in London. They were received on 27th July. Seven pictures survive: four of a Defiant/Supreme amplifier section, three of a Foundation/Super Foundation Bass. The bass model had Tone-X, designed by Sava Jacobsen while at Thomas.

Second half of 1966: an overview of the character of a typical set of pre-production JMI circuit boards is now available here.

Late August '66: a promotional Vox Conqueror and Supreme exhibited at the BMII Trade Fair at the Russell Hotel, London, 22nd to 26th August, 1966. It may be that bass models were exhibited too.

The Conqueror exhibited at the Russell Hotel, London. For more on the Fair, see this page. The Guardian newspaper reports that orders were taken for the "new range" of transistor amplifiers. These will not have been met until the Spring of 1967.

The JMI brochure for the Australian market reproduces the first attempt at a footswitch. Note that the "Virtuoso" at this point was the "Supreme". What we now know as the Supreme was called the "Beatle".

Detail from the Australian catalogue, late 1966.

Later 1966: a small number of pre-production amplifiers are made in the Vox Works at Erith. A surviving pre-production Dynamic Bass retains its original inspection tag, dated 12th January 1967. Standard production amps were being mapped out at this time

Pre-production Dynamic Bass

Late 1966 / early 1967: the pre-production amps were given to bands to try. Manfred Mann and Blossom Toes were issued with Supremes. Manfred used his until c. 1970 with a Vox 4120 speaker cabinet.

Manfred, Berlin, 1967. As in all pre-production amps, the speaker socket is at left on the back panel, the mains socket far right.

Late 1966: the range is redesigned, cosmetically and to some extent electronically. Feedback from the bands on the pre-production models had doubtless raised some difficulties.

November 1966: Burndept Electronics begins procurement for the standard production amplifiers. Its parts lists (twelve sheets) for the power section of the Supreme and Super Foundation Bass survive.

Early January 1967: the announcement is made in "Beat Instrumental" magazine that the new range would be available at the end of the month. But this did not happen.

February and March 1967: advance production of the new designs begins. By late April, around 100 Defiants had been made.

Late Feb. / early March 1967: the new solid state amps are "a secret", for the continental market at least, until the Frankfurt Musikmesse. The German catalogue (dated March '67) is printed to coincide with, or follow, the Fair.

"Midland Beat" magazine, March 1967. The Frankfurt Musikmesse took place from 26th February to 2nd March '67.

Mid March 1967: The Stones are issued with two standard production Supremes and a Super Foundation Bass amplifier. See this page.

April 1967: the new JMI pricelist for the UK is issued. "Beat Instrumental" magazine relates elliptically that the range is now available.

For some material on production, see this page, which has recently been updated.