VOX AC100 - UPDATES AND NEW INFO
A great picture from the Daily Mirror of Jet Harris (in the white jacket) on stage with Sounds Incorporated at the NME Poll Winners Concert, 26th April, 1964. Note the stacked pairs of Foundation Bass cabs at the extremities of the stage.
The performance caught in the photograph.
For more on the venue, the Empire Pool, Wembley, see this page.
10th February (2)
AC100 serial number 813; chassis number 1469. An AC100 Mark 2 from the last quarter of 1965. The brimistor has been removed. Further pictures to follow.
A new page gathering together adverts and promotions for the AC100 in magazines and periodicals has been started here.
Further JMI promotional material from 1961-1962 added on the main documents index page (click on the image above).
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.
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, Finsbury Park Astoria, 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.
"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.
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
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.
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.
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.
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.
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)
"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.
30th December (3)
The new index page for the JMI documents:
Click to go to the index page. Captioned links are given to the items that have been posted so far.
30th December (2)
The documents from 1961 and 1962 are now being assembled on pages of their own:
Illustrated catalogues and coloured flyers to follow.
1962 - the pricelist following the phasing out of the AC30/4. The AC30/6 (AC30 Twin) is now 115 guineas. See the first entry for 29th Dec., below.
29th December (2)
Below, a TCC (Telegraph Condenser Company) folder of technical bulletins from 1962, just arrived. Green TCC micromite electrolytics were used in AC100s from early 1965 through to 1966.
Again, values are given both for "Peak Working Volts" and "Surge Volts".
A 32uf 350v TCC micromite in AC80/100 no. 392.
One of the documents encompassed in a batch sent out in November 1961 in response to an enquiry - see the Jennings form letter below, 16th December.
Various new things are in train: the add-on tone circuit; the AC10 and AC15 twin; the AC30 super twin; and the discontinuation of the AC30/4.
The pricelist corresponding to the announcement. Note that the AC30 (six input) twin is 100 guineas.
Some more screengrabs from the BBC documentary on Screaming Lord Sutch and the Savages, filmed in late 1964, produced and aired in 1965. Shots of Ricky Fenson, the group's bassist, putting the AC80/100 in the Commer van after a gig.
Some notes on Paul McCartney's 2x15" brown-fronted speaker cabinet, used through to the end of the USA autumn tour, 1964:
A detail of amp and speaker cabinet, Washington Coliseum, 11th February, 1964. In the sliver below, one can just see the BASS flag of the cab.
Just visible, the BA of the BASS runner.
Amp and cab on stage, New York, Carnegie Hall, 12th February, 1964.
Adelaide, 12th June, 1964. The cab's BASS runner has gone.
Las Vegas, 20th August, 1964, detail of the speaker cabinet with Paul's second brown-fronted amp.
Not Las Vegas, but Forest Hills, 28th August.
Above, Toronto, Maple Leaf Gardens, 7th September, '64. At some point before the autumn tour of the States, the cab evidently had a new connector fitted - a rectangular Cannon. The original circular Cannon can be seen below, backstage at Versailles, 14th Feb., '64.
The mark left by a drip underneath the handle/recess can also be made out in the photo above.
New Musical Express, 1st May, 1964. Vox advert for the Poll Winners Concert. The images were first used as an ensemble in the Vox advert for the Dave Clark Five in February '64. Note that the "A.C. 50" is actually a T60.
New Musical Express, 16th April, 1965. Poll Winners Concert ad.
A note on AC100 output transformer connections - 8 and 15 ohm. Below, schemas of the three main types: early cathode bias (copper and black panel amps); later cathode bias (grey panel amps); fixed bias ("100W Amplifier" and AC100/2).
The output terminal block of serial number 392, later cathode biased.
In the schemas above, the position and colour of the wires from the transformers are given in their most common order. In all types of AC100, however, one sometimes finds the common in the centre. The output transformers of early cathode biased amps have more complex windings (resulting in pairs of wires feeding into the terminal block).
AC100 Super Deluxe (SDL) speaker cabinets; 2 x 15" bass units; and the majority of Foundation Bass cabs had an impedance of 8 ohms, naturally requiring the output connections to be set for 8 ohms on the amplifier too.
By early 1965, a 470 ohm resistor was introduced across the 8 ohm tap to help guard against open circuits.
Detail from the "100W Amplifier" circuit of late summer 1965. L/S is "loudspeaker".
Effectively, when no speaker cabinet is connected, the 470 ohm resistor provides a load that the amplifier cannot "drive" - a sort of surrogate if you like (impedance is not identical with resistance) for a 470 ohm cab, not quite a dead short, but close. The protection afforded by the resistor is necessarily short term - enough to give time for a switch off following the discovery that no speaker cabinet is attached - but it is protection nonetheless. Hiwatt used a similar resistor over its jack socket ouputs.
When a speaker cabinet is connected, the 470 ohm resistor lies in parallel with the 8 ohm load of the cab. The effect of the resistor then becomes negligible. The product of the two resistances (one technically an impedance) in parallel is a little over 7.8 ohms.
16th December (2)
A little more on tags - see the entry below, 15th December. A number of Scandinavian countries had laws in the 1960s and 1970s that made voltage selectors illegal. The selectors were consequently removed and the mains input hardwired for 225v. Ingeniously, the black and gold tags were sometimes used to fill the hole.
An AC50 from late 1965 / early 1966.
A note relating to early Jennings Musical Industries, not really germane to anything here, but interesting for process. Pictures of a largish trove of early Jennings catalogues, flyers and brochures, some not available elsewhere (web or in print), may follow.
A good selection of catalogues, flyers and pricelists accompanied this letter, sent to the enquirer, who lived in Scarborough, in November 1961. A further batch was forwarded in 1962.
Five Jennings Musical Industries patent applications, 1955-1963 - inventions of Les Hills and Derek Underdown for organ and guitar elements - can be found here.
Use the menu at the side of those patent pages to find copies of the original documents and drawings. Various dates are recorded - of submission, deposition, approval.
Les Hills, the genius behind the T60 amplifier and numerous organ circuits, continued working and innovating for Vox through to "Vox Sound Equipment Limited" days - see the patent for a polyphonic keyboard voicing, January 1969, on the Vox Supreme website.
Scarce these days, but by no means unique, a couple of JMI tags for English-made equipment, on the left the early style (to the last third of 1964), on the right the style that followed (last third of 1964 to 1968). The one on the left, originally attached to AC50 no. 1101, will have been the type accompanying copper panelled AC80/100s (thanks to Martin for pointing that out).
AC50 no. 1101, diamond input, second third of 1964. The amp is gone, but shop price tag, JMI guarantee, envelope and tag survive.
A number of the later style tags are still on or with the amps they were issued with:
Above, AC50 no. 5619, from 1966.
Defiant no. 1102, from April 1967. Thanks to Paul for these pictures.
The tag was presumably redesigned - a third style/type - in the summer of 1968 to omit "JMI". The succeeding companies were "Vox Sound Equipment Limited" (summer 1968 to early 1970) and "Vox Sound Limited" (summer 1970 to early 1973).
A "Vox Sound Limited" Supreme (1972). Picture from donkey's years ago. Presumably the tag simply has VOX.
There is I think a late AC100 in Germany also with a tag, but the picture has decided not to let itself be found for the time being.
A better version now of the Vox advert following the NME Poll Winners Concert, May 1967 - the line-up was mainly new solid state Vox Supremes and Super Foundation Bass amps. The Queen's award for Industry had been awarded in April 1967 - see this page.
NME magazine, 13th May 1967. All the bands on the bill used the equipment supplied by Jennings (there are small pictures throughout the 13th May issue). In the quadrants of the circle going clockwise: Dusty Springfield at the NME Concert, 1965; equipment on stage, also 1965; the Beatles with a 7120, Abbey Road, April 1966; Cliff Richard at the 1967 concert.
A better version (below) of the Vox advert following the NME Poll Winners Concert, May 1966, now posted on at the Empire Pool, Wembley page.
NME magazine, 13th May, 1966. The AC100 is still the picture (four were supplied by Jennings for the concert). The glimpses of The Beatles, Stones, and Dusty Springfield are from the NME Poll Winners, 1965. Pictures from the '65 concert were also used for promotional purposes in the States.
A new page begun on the equipment supplied by JMI for events at the Empire Pool, Wembley, 1964-1968.
The main front of the Empire Pool, 1st July 1967, fans arriving for the Monkees - equipment supplied by Vox.
A second page illustrating the equipment supplied to smaller venues and events to follow.