The MC15 as represented in an advert published by JMI in the music trade press, December 1964.

From 1964, Public Address equipment became an important part of the Jennings catalogue. Amplifiers of various wattages were offered, along with column and wall-mounted speakers, a large selection of microphones, mixer units and so on. Triumph Electronics in Purley was contracted to produce the amplifier sections

Unlike its fellows, the MC15 was not modular in nature. Whereas the preamp assemblies of the MC30, MC50, and MC100 were interchangeable (same shape, size, same eveything), the MC15 had a format of its own, extremely compact, and cleverly designed.

The entry for the Metal Clad amplifiers in the catalogue printed for JMI in February 1964. The earliest amps were evidently very different - two inputs, master volume, an array of speaker ouputs, and so on. During the course of 1964 the range was redesigned. Only the larger amplifiers had multiple speaker connectors and a 100v line.

JMI pricelist, as above, printed February 1964.

The intended use of the PAs was (as set out above): "For factory, theatre, club, pop groups, etc..". For small meeting rooms or spaces the 15 watt and 30 watt amps will probably have been fine. Jennings naturally kept its eye firmly on the competition, joining the "Assocation of Public Address Engineers" in late 1963 and taking part in its exhibitions and meetings - see see this page.

JMI pricelist of November 1965.

JMI pricelist of April 1967.

As for the export market, only the MC50 and MC100 figure in French, German and Italian Vox catalogues of the mid and later 1960s - the MC15 and MC30 are not mentioned. It is worth noting too that the range as whole was not offered at any point in the USA. The Metal Clads did not form part of the "deals" made with Thomas Organ.

Quite how many MC15s were produced is difficult to gauge - probably not that many. At any rate, none has so far been identified in the small ads in Melody Maker magazine.

As in the case of the rest of the range, the serial number sequence employed belonged to the corresponding range of guitar amplifiers, in other words the AC15. MC30s had numbers in the main AC30 sequence, MC50s in the AC50 sequence, and so on.

Thanks to Oly, pictures of MC15 serial number 5594, probably third quarter of 1964, an extremely rare survival. The serial number plate is machine stamped "AC15" and then the number. "MC" was hand-stamped to indicate the model was actually a Metal Clad. 5593 is likely either to have been an AC15 combo or twin.

PREAMP: two ECC83s as drivers for the four channels (one ECC83 triode per channel); and a third as a phase splitter. The chassis has an unused cut-out either for a further valve or possibly filter capacitor.

The amp has four channels / inputs - three for microphones, one for music - each with its own volume control. Overall treble and bass controls are provided at right (above the mains switch). The plastic input jack sockets are Rendars, as used by Triumph in the early AC50s it assembled under contract for JMI.

The Mullard mustard capacitors have a range of date codes: "A/63" and "A3N" (first quarter of 1963); "B3N" (second quarter of '63); and D3N (last quarter of '63). Resistors are for the most part white Eries, along with a handful values with green and brown bodies - again, typical of Triumph production.

Valve bases are fixed to stand-offs underneath the chassis apron such that the ECC83s slot down through through the cut-outs. This was to keep overall height of the assembly to a minimum.

POWER SECTION: two EL84s and an EZ81 (not EZ80 as stated initially) rectifier valve. Transformers were sourced from JD Electronics in Corsham, Wiltshire (registered office only in Birmingham). An output transformer with the same part number - "MS377" - is found in AC15 Twin serial number 3874.

The OT, in common with those used in other JMI amps, makes provision for 8 and 15/16 ohm loads. The speaker connector is a Belling Lee L1469, a sort of right-angled terminal block. To connect a pair of 16 ohm speakers, one would feed the two common or "ground" wires into the common ("0") tap, and the two "hot" wires into the 8 ohm tap, the speakers standing in parallel in relation to the amp as far as total impedance is concerned.

Note that the power valves have slanted bases, cocking the valves at angle to reduce height - a trick later used by Triumph in early production UL7120 amplifiers.

On to the page on the Vox MC30 amplifier.