Jennings Electronic Industries AC100

Autumn 1972 - mid 1973

Dick Denney in C&W finery at the Jennings stand, August 1972 (picture published in September), an AC100 in the background. There was a definite "Wild West" theme to some of Jennings's adverts and guitars.

The AC100 was the third all-valve amplifier issued by Jennings, its precursors being (in order) the AC40 and AC15.

Although no published note of its introduction has come to light so far, a picture printed in the trade press (above) shows that an AC100 was certainly on show at the Russell Hotel Trade Fair, August 1972. Whether the model had been exhibited in some form in the Jennings displays at Frankfurt in February and Chicago in June is unknown.

Published by Jim Elyea in his superb book on Vox amplifiers, a flyer for the Jennings AC100 probably printed in summer 1972.

The amp was designed initially - in 1970/1971 - by Dave Roffey of Triumph Electronics for Vamp, for whom Dave later worked. In early 1972 Johnson Amplification, owned by Geoff Johnson who also owned Triumph, produced its own version; then at the end of '72 it was marketed, with appropriate change of logo and cloth, by Jennings.

Triumph of course was not only already assembling Tom's 50 and 100 watt transistor amplifiers, but it had done much work for him in JMI days, prototyping, producing runs of amplifiers, and so on. A ready-made design (in the shape of Dave Roffey's AC100) will have been a great asset.

Jennings's other contractor, A.P.T. Electronics of Byfleet, probably produced solid state sub-assemblies for amplifiers and organs.

Beat Instrumental magazine, April 1972. The 100W Universal Amplifier later sold by Jennings.

The pricelist of December 1972. The full list is available here.

Beat Instrumental, Jan. 1973, itemising Jennings prices.

In the summer of 1973, the JEI AC100 became the JEI V100, the outer case radically changed - part of the revamped "purple" line - but the chassis kept more or less the same. A major departure, however, was the addition of reverb. See this page.

Some surviving amps

100 watt output. Two channels: bass and lead. The lead channel has volume, bass, mid, treble, and "bite" (preamp distortion) controls. The bass channel: volume, bass, treble, and boost. A master volume is provided far right. Four ECC83s serve the preamp, four EL34s in the power section.

A variety of speaker outputs are provided to allow for different impedances resulting from combinations of speaker cabinets. There is also a dedicated output for a slave amplifier.

The earliest AC100s have familiar Jennings "chain-mail" grille cloth and plain metal control panel. Later ones (1973) have a variety of thicker woven cloths and black panels.

The serial number sequence begins at 2000. The highest number definitively known at present is 2035 (below). Production numbers are unrecorded but not likely to have been great (fewer probably than 100).

An early AC100 in standard Jennings cloth

As above, first style Jennings grille cloth. 4 x EL34s, and three ECC83s, two for the preamp, the other the phase splitter, on the upper chassis (surrounded by an alumiumn guard). Early "Johnson" AC100s are similarly arranged. In slightly later amps the circuit was revised and the upper and lower chassis laid out differently - see below. Thanks to Joe for the pictures.

Serial number 2031

Brown cloth as below, but early style of chassis.

A slightly later amp in brown Jennings cloth

Serial number 2035 - currently in Germany

NEW

In superb original condition. The red CCL filter capacitors bear the date code "D71" = April 1971 for their manufacture. The valves are ERA-branded EL34A, the ECC83 made in GDR. One of a group of amps not fitted with a logo or serial number plate. Inside the wooden case, the name "Eleanor", likely to be one of the ladies responsible for "finishing" - adding the grille cloth, piping, and so on. Thanks to Angel for the pictures.