Later Vox MC100 public address amplifiers
Late 1965 - 1968
For early Vox MC100 amplifiers, 1964 to 1965, see this page. "MC" stands for "metal-clad" (metal case). Details of the numerous Vox Public Address amplifiers and Line Source speaker cabinets on offer in the small ads of "Melody Maker" magazine are being collected together here.
Below, Dick Denney at the "British Musical Instrument Industries" Trade Fair, August 1964, with one of the new metal-clad 100/6s, transistor preamp, valve power section. The new part-transistor, part-valve MC50/6 was released at this time too.
Dick Denney at the British Musical Instruments (Association of Musical Instrument Industries - AMII) Trade Fair, Russell Hotel, London, 24th - 28th August, 1964, a six-input PA to his left. See this page for further details on the Fair. In the picture immediately above, two PA amps are visible.
Above, the blurb from the review of the British Musical Instrument Industries Trade Fair, August 1964, published in "Beat Instrumental" magazine, October of that year, setting out the rationale of the PA amplifiers - presumably springing from what Denney and Reg Clark (JMI Sales Manager) had said at the Fair. The text straddles an unrelated picture which has been omitted.
A detail from a catalogue of 1965
The MC100 mark 2.
At the Russell Hotel Trade Fair of August 1965, Jennings showed several new lines of PA equipment, among other things, the MC150 and Line Source 60 (LS60) column speakers, indicating that the cases/cosmetics of the Metal Clad amplifiers would soon be revised.
Item from the review published in "Beat Instrumental" magazine, October 1965, of the British Musical Instrument Trade Fair at the Russell Hotel, London, August 1965. The new style of Vox PA amplifiers unveiled, evidently regarded as being a stop-gap as far as cosmetics were concerned.
A detail of the JMI pricelist of November 1965.
Below, the information panel of the JMI circuit diagram for the MC100/4 mark 2, drawn out by Albert Hogben on 18th June 1965, i.e. shortly before the Trade Fair at the Russell Hotel in August. The new sheet for the MC100/6 has yet to come to light.
A detail of the information panel of OS/086 for the MC100/4 mark 2.
The amplifiers below, with blue/grey fascias, are the result of the revised look of the range signalled in August and September 1965.
Surviving amps from 1966 - 1968
The revamped range of 50W, 100W and 150W public address amplifiers was put into production for Vox by Triumph Electronics, the blue/grey and white livery also applied to the growing array of Vox Effects Units, PA Mixers, and other devices.
In terms of electronics, a notable feature of the 100W PA amps is the provision of individual bias controls for the output valves, similar to those of the Vox UL 4120 and UL 7120, which were also assembled (and part designed) by Triumph.
The units with a transistor preamp - the MC50/6 and MC100/6 - were considerably more expensive than the all-valve MC amplifiers due to the complexity of assembly of the circuit boards. But the list price at least remain stable from 1965-1968.
Detail from the JMI pricelist of April 1967">
The MC 100/4
By 1966, a redesigned box, normally grey hammerite, but sometimes black; a blue/grey fascia. In common with MC50/4s of the same type, the preamp has four ECC83s. The power section has EL34s, and transformers manufactured principally by Drake. Occasionally one finds Wodens. Several permutations of speaker outputs were possible.
The JMI circuit diagram was OS/086.
Image from the Vox catalogue of 1966
The band Styler's Musical Express playing at the Lion Hotel, Singapore - note on the centre of the riser a metal-clad PA much as the 100 watter below.
The Yardbirds, April 13th, 1967.
Serial number unknown - currently in the UK
A monster from 1966 in good physical and cosmetic condition. Many elements are similar to the 7-series amps - tagboards with eyelets (instead of hooks), Mustard capacitors, insulated stand-offs on the chassis, and individual controls for the output valves' bias on the back panel. The EL34s are the original ones, with Mullard date codes B5G2 = Blackburn Factory, 1965, 2nd week July.
Serial number unknown - currently in the UK
Similar to the PA100 above but later. Pot codes "LN" = December 1966. Used by the English band "Moonstone" in the early 1970s. Serviced and re-valved by Alan Pyne in 1979. Further pictures to come.
The MC100/6
Transistor preamp, valve power section (four EL34s). Six channels: five for microphone, one for music, each with a dedicated volume control. Overall volume, treble and bass controls. Upper left on the fascia a multi-position switch and meter to display power output and the individual bias voltages of the power valves. Various permutations of speaker output were provided.
Detail of the image used to advertise the MC50/6 and MC100/6 in the JMI brochure produced for the German market in March 1967. Although there is no "50" or "100" on the front, the amp is probably a MC50/6. The MC100/6 has an indicator lamp above the mains switch. In the brochure the MC100/6 is priced at 2198DM, the equivalent at the time of £200 - substantially more than the price in the UK.
Serial number unknown - currently in the UK
Currently in the UK, a rare PA 100 with power meter. The transistor preamp looks good and intact; the power section does require a little attention though. Two of the four EL34s were replaced at some point by 6L6s.
June 2013 - the amp now beautifully restored and in full working order. Thanks to Mick for the pictures.
MC100/6 type 2
Four speaker outlets
Serial number unknown - currently in the UK
Sold on ebay in September 2014. Box and power meter missing, but great condition. Assembled by Vox for Triumph Electronics. The preamp, as above and below, is solid state. Power section is all valve with individual bias controls for the EL34s.
The transformers were evidently supplied by Drake - note the format of the part numbers. Mains: 1204-66B. Choke: 352-169. Output: 1202-111.
In terms of date, one of the Hunts caps has the date code "NYW" = first week of 1966. For more on the Hunts dating system, see this page on the Vox AC50 website. That one of the pots has the code "AO" = January 1967, indicates however that the amp was probably produced in the first half or perhaps first third of that year.
The same amp as above, cleaned up and with the addition of a power meter.
Serial number unknown - currently in the UK
Sold on ebay.uk in early 2014. Just the power amp chassis, but in good condition. This is a larger (wider) unit, as above, with four 1/4" jack outputs rather than paired round Bulgins.
Serial number unknown - currently in the USA
Again, four 1/4" jack sockets for the speakers. The power cable now hard-wired, feeding through a hole next to the Bulgin. Thanks to Robert for the pictures.
1967 - full solid state
In early 1967 the plan was to replace these amps with a new all solid state version, part of the line of all solid state guitar amps (the Conqueror, Defiant, Supreme, and so on):
Above, the amps in the solid state catalogue of early to mid 1967. No surviving examples have hitherto been seen however. For further info on the solid state range of amps, see the Vox Supreme website. A synopsis of some of the material can also be found here.