VOX AC100 - UPDATES AND NEW INFO
January 2019
30th January
Part of the preamp of an AC80/100 produced by Westrex for Jennings. The two pink-coloured resistors indicated by the arrows are the 220K plate resistors of the ECC82 phase splitter - 1/2 watt Welwyn "Panclimatics" (type C22), carbon film on a ceramic rod, brass end caps. They were chosen for their low noise and high stability - to keep the two halves of the ECC82 balanced.
Later AC80/100s produced at the Burndept / Vox Works in Erith have 1/2 watt white Erie resistors, in line with the rest of the preamp, in this position.
27th January
A short note on early AC100 SDL cabs in reference to the report in Melody Maker magazine, 25th July, 1964 (posted below, 26th Jan.) - "The four loudest amplifiers in the beat world....":
The amplifiers were not new at this point, but the Super De Luxe cabs were: four Celestion T1088s and two Midax horns. Early cabs were different from standard production units in two principal ways: the XLR speaker socket was on the lowest of the three backboards rather in the middle; and the cross-over network to protect the horns was far more complex.
The backs of the two cabs issued to George and John, refurbished and in new trolleys, can be seen on stage at Paris, 20th June, 1965. The original trolleys with basket tops had evidently served their time. For some good shots of the early trolleys, see this page.
Click as ever for a larger image. Picture courtesy "Getty Images". Note the rectangular Cannon XLR socket on the lowest backboard. The cabinets do not have corner protectors. See also the pic. a little way below.
Below, a detail of the cab discovered by Mitch Colby in Denver (accompanied by AC80/100 serial number 225), similarly arranged. In the picture above, one can just see the capacitor boxes in the well of the cab at left.
Further pictures are here. Amp and cab are likely to have been JMI loan/demonstration equipment.
The Stones, Paris, 20th October, 1964, with a JMI loan AC100 SDL - speaker connector on the lowest backboard. The early trolley with basket for the amp to sit in can clearly be made out.
Whether the four cabs above were the four referenced in the "Melody Maker" notice is impossible to say at present, though it would of course be nice to think so. Perhaps a second batch was produced in fairly quick order after the initial four.
Rehearsals for the Christmas Show, Hammersmith Odeon, December 1964. Picture courtesy The Beatles Book Photo Archive. Note that George's cab has no corner protectors - the form of the curve at the corners is different from standard production cabs. The old basket top trolley is still present.
Jeff Beck, afternoon of 6th August, 1965, with the AC100s loaned by JMI to The Who for the Richmond Jazz and Blues Festival. The cab on the left, with the bagging grille cloth, has an old basket top trolley.
26th January (2)
"Melody Maker" magazine, 21st March, 1964. A great advert celebrating the opening of the "Sound City" shop on Shaftesbury Avenue, London.
Throughout the second and third quarters of 1964 Jennings promoted the T60 fairly intensively. Amp and cab appear no less than three times in the ad above.
26th January
"Melody Maker" magazine, 25th July, 1964.
The amps in question were the AC100 SDLs designed for John Lennon and George Harrison. Paul's AC100 bass had been issued to him in late December 1963.
It is interesting to note that four were produced initially. Two were given to the Beatles in the first week of August '64. The other two were evidently retained initially for promotional purposes, being shown at the "British Musical Instrument Industries" Fair (24th-28th August) while the Beatles were on tour (18 August - 20th September).
On the Fair, which took place at the Russell Hotel in London, see this page.
19th January
Above, what has claim to be the earliest advert for the AC100 SDL - an inset in "Melody Maker", 12th September, 1964. If an even earlier one turns up, it will not be by much. The Beatles received their SDL cabs in the first week of August 1964. Amps and cabs will only have been widely seen on the USA tour - note the context in the first lines of the ad ("current U.S.A. Tour") - 18th August to 20th September.
It is interesting that the AC100 SDL was not advertised in "Beat Instrumental" magazine, a paper aimed at professional musicians, until Spring 1965. Perhaps it was just a question of circulation.
Note that the amplifier in the drawing is in a thick-edged box. The first we see of an actual example is on stage at the Empire Pool, Wembley, 20th November, 1964. See this page.
Thick-edged boxes measure: 19 3/4 x 11 1/2 x 7 1/2 inches. The height given in the advert however is 8 1/2". Either some mistake crept in or Vox had begun thinking along slightly different lines: 8 1/2" tall suggests a chassis on a slider board, perhaps akin to the large box AC50.
Thin-edged boxes - the earliest type (see for example this page) - were 19" x 11 1/2" x 7".
Below an early AC80/100 in what may be an original experimental box. The box is considerably larger however than the one envisaged in the advert. It measures: 22 1/2" x 11 1/2" x 9 1/2" (the height of a large box AC50). The amp sits on a slider board.
A better image of the above to follow.
The full Vox advert, 12th September, 1964
13th January
Advert for VOX placed by "Musicland" in the TV Times, November, 21st - 27th November, 1964. The shop regularly placed ads in daily newspapers throughout the early 60s, only occasionally in other sources though - the TV Times was an occasional.
Vox printed up various brochures, flyers and pricelists specially for "Musicland".
Cash and Hire Purchase terms from 1963.
12th January (2)
A JMI brochure from 1961 printed for "Musicland", Broadway, Bexleyheath, Kent. "Musicland" was a long-standing Vox dealer. General views on the early documents page, details to follow.
12th January
Catalogue of the Radio and Electronic Component Show at Olympia, May 1963. All the big manufacturers were there, including Burndept Electronics under the mantle of Royston Industries. Jennings Musical Industries of course did not participate, but many of its component suppliers had stands. This was the sort of show that JMI engineers will have attended.
Amphenol - see further this page.
Arrow switches, used throughout the 1960s by JMI.
Cannon XLRs - full page advert and link below.
Dubilier - see further this page.
Erie resistors - used by JMI in AC80/100s from spring 1965.
Rola Celestion speakers.
Welwyn wirewound resistors - used in the cathode bias circuit of AC80/100s and where load resistors were required on main drive voltage lines.
The Welwyn entry in the catalogue.
Woden Transformers - see further this page.
Cannon connectors - see the entry below for 6th January, and this page.
10th January
A better detail of the JMI promo / dealer photo of the Stones. Large parts of the (empty) thin-edged AC80/100 box - not just the logo - are painted in.
9th January
A detail of the JMI loan AC80/100 (thin edged box) used by the Stones at Olympia, Paris, 20th October 1964. Photo by Roger Kasparian. The back panel is distinctive, corners of the connectors hard by the screws on the bottom edge, and the top left corner of the warning plaque hard by the screw on the left-hand side.
A larger detail. To the side of the SDL, an early thin-edged AC50 with its Foundation Bass speaker cab.
6th January
Separate pages have now been added on Cannon mains and speaker connectors, and Amphenol connectors. The relevant part numbers are given for reference.
The rough "rule of thumb" for speaker sockets and connectors on JMI amplifiers is:
1963 to mid 1964 - circular Cannon female sockets on the amp, sometimes the speaker cabinet too - one also finds female on the amp, male on the speaker cab. Male or female Cannon connectors on the cable.
mid 1964 to mid 1965 - rectangular male Cannon sockets on the amp and speaker cabinet. Female Cannons on the cable.
mid 1965 to 1968 - male Amphenol sockets on the amp and speaker cabinet. Female Amphenols on the cable.
The connectors envisaged in Thomas Organ parts list from 1967 - available here - are probably Amphenols:
09-5407-0: Speaker Cord - 12 foot (complete)
09-5408-0: Speaker Cord Socket only (For Cable)
09-5409-0: Speaker Cord Plug only (For Cabinet)
5th January
"Flight International" magazine, July 1964. Advertisement for Amphenol - the new factory at Whitstable, on the Kent Coast, around 40 miles from the Vox Works at Erith.
Amphenol connectors were first adopted by Vox in mid 1965. Up to that point Cannons had been used.
It may be that Amphenols were suggested by Thomas Organ, which was in mid '65 in the process of setting up its own line of amplifiers - the solid state "Super Beatle" (fitted with Amphenol speaker connectors) - and so on.
Well to note too that Burndept Electronics, with whom Vox shared the Erith Works, had long been involved in avionics - notably in the mid 60s the Midas flight recorder, which raised doubts from the first.
The Observer, 22nd November, 1964. Prophetic words.
