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.

The intended use of the PAs was expressed in the full line catalogue of 1964 (illustrated below): "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", and taking part in its exhibitions and meetings - see see this page. Demonstrations of the Vox Wireless Radio Mic system were undertaken, but nothing else is mentioned - expressly at any rate.

Although we do not know precisely how many amps were made, reasonable numbers can be found in the advertisements placed by shops in the back pages of "Melody Maker" magazine - i.e. a small but still useful cross section of sellers. Relatively few units have survived though: some MC50s and MC100s. But so far no MC15s, MC30s or for that matter MC150s have come to light. The 1970s and 1980s were not kind to old PA gear. A page on early MC50s can be found here; later ones are here.

"Melody Maker" magazine, 6th May, 1965. A Vox 30w PA set at Len Stiles in Lewisham.

From time to time, guitar amps were also supplied as part of PA sets: AC30 Super Twin and AC50 amplifier sections with pairs of 4x10" column speakers; and AC100s either with a pair of 4x12" colums or two 2x15" cabs.

Sold on ebay some time ago - an AC30 serving as a PA amplifier with two LS40 speaker columns. One occasionally finds adverts for these sets in the music press.

Foundation Bass cabs were occasionally pressed into service too. Below, the NME Poll Winner's Concert at the Empire Pool, Wembley. Vox regularly provided equipment for important events at the Pool. Cyril Stapleton and Alan Harding from JMI normally went along to make sure that everything was miked up properly. The difficulty was getting the bass to sit properly in the mix.

The NME Poll Winner's Concert, Empire Pool, Wembley, April 1963, Jet Harris on stage. Note the stacked Foundation Bass cabs at the sides of the main stage.

Circuits

Although no MC30 has survived, nor any JMI circuit diagram ("OS" sheet) for its electronics, it seems likely that the amp's power valves ran in fixed bias, unlike the AC30's, which were cathode biased. Fixed bias was the topology used for MC50s and MC100s. It seems likely too that Triumph produced several variants of MC30 (and the MC15) - a series of "Marks" - much as it did for the larger amps. Very provisionally:

Mark 1 (1964) - valve rectified, sloping front, metal fascia, grey hammerite case.

Mark 2 (1965) - solid state rectified, flat front, metal fascia, grey hammerite case.

Mark 3 (1966-1968) - solid state rectified, flat front, blue/grey fascia (?).

Mark 4 (1966-1968) - transistor preamp (?).

Pure speculation, but given that one of the "Marks" of MC100/4 was circuit diagram OS/086, the sheets for the MC15/4 and MC30/4 in late 1965 may have been OS/083 and OS/084.

Some relevant documents, 1964-1970

JMI catalogue, early 1964. Note the prospective applications - "For factory, theatre.....".

Detail from the JMI retail pricelist, September 1964.

Detail from the "Precision in Sound" newspaper-style catalogue, late 1964 / early 1965. Three surviving MC50s have the same sloping front.

JMI catalogue, 1965. The 100 watt unit was shown for the first time in the format illustrated at the Russell Hotel Trade Fair, August 1964. To the left of the meter on the front was a multi-position switch that enabled one to see (on the meter) the individual bias voltages of the four EL34 power valves and the total power out.

A detail from the pricelist of November 1965. The 150/6 was introduced for the first time at the Russell Hotel Trade Fair in August. Also presented at the Fair, a PA amplifier with built in reverb and echo - but that is unlikely to have made its way to production.

From late 1965 to 1968, the roster of PA amplifiers remained much the same - 4 inputs for the smaller models and a choice of 4 or 6 for the larger. MC50s and MC100s were either all valve, or transistor preamp with valve power section. Triumph built the amplifiers in varying ways in 1966 and 1967. No two are exactly the same.

JMI prices, April 1967

On to the page on the Vox MC50 amplifier.

Back to the main index page on Vox Public Address equipment.