The solid state Jennings J40, one of the most popular amps of Tom's new range, was introduced in mid 1968, having been developed alongside the J100 - on which, see this page. Both were exhibited in public for the first time at the "British Musical Instrument Industries" Fair in August 1968. By the time the J40 was deleted from the catalogue, at least 500 had been sold.

An extract from Beat Instrumental magazine, August 1968, reporting on the BMIIshow. Mention of "transistor amplifiers from 40-100 watts" encompasses the J40 and J100. At this time the company was "Jennings Electronic Developments". In 1969 it became "Jennings Electronic Industries".

The J40 preceded the Jennings AC40 (an all valve descendant of the Vox AC30) by around eighteen months. For Tom, it was solid state amplifiers first.

Detail from the Jennings Electronic Developments catalogue of late 1968 / early 1969, produced in advance of the Frankfurt Trade Fair of late February.

To judge by the blurb above, the initial drive was to make the J40 as versatile as possible - auxiliary inputs for "tape recorder, record reproducer", and so on. See the first two examples in the section on "Surviving Amps" towards the foot of this page. It is clear that early J40s were constructed and detailed differently.

In the newspaper-format catalogue printed for the Russell Hotel Trade Fair of August 1969, conventional specifications were given, however - standard form for amplifiers intended for guitarists and organists.

Detail from the Jennings catalogue of August 1969.

Above, a section on JEI in the "Focus on Amplifiers" published by "Beat Instrumental" magazine, February 1970. The J40 cost £130.

Through to late 1972 the J40's recommended retail price remained relatively stable - only a £10 increase by December of that year. In mid 1973, it was reduced by 10 per cent. A few months later the J40, J100 and J100D were deleted from the Jennings catalogue, though it is clear that some continued to be sold.

Jennings pricelist, December 1972.

Brief list of prices published in June 1973.

In common with the Jennings J100 (and certain amplifiers in the Vox solid state line), the J40 has a three-position mid-range boost switch, position "0" being off, the other three (1-3) switching in an inductor and capacitor network to provide different resonances. The circuit was Dick Denney's design, going back at least as far as late 1964.

No circuit daigram for any Jennings Electronic Industries amplifier has so far come to light unfortunately. Thanks to Steve Walsh, some provisional notes however: - generally remarkably similar to the circuit in the Vox Phantom Special. Take the normal channel on a Mk1 Conqueror but instead of those tone controls, attach the tone stack from the brilliant channel with the MRB. The presence control switches between two different caps or no connection at all. The Tone switch is unusual. It seems to break the connection between the pot wiper and three caps of mrb, resulting in a considerable reduction in volume.

From mid 1969 - see this page - assembly of chassis is likely to have been undertaken by the APT Electronic Group of Byfleet and Ascot. Speakers are Celestion alnicos, apparently T1096s, wired in parallel for a total impedance of 8ohms.

JEI speaker impedance warning sticker. These were pasted inside the speaker compartment of J40s.

Early - serial number unknown

An early Jennings J40, secondary panel at rear. The back panel has a central cut-out similar to the ones that Denney devised for the Beatles' early AC50 speaker cabinets. Denney of course was Tom's right-hand man at the new company.

Serial number 546

Power section at rear, as in the amp above. Note too that the graphics on the control panel are different from those of the amps below.