VOX AC100 - UPDATES AND NEW INFO
June to August 2022
A JEI D4 speaker cabinet from late 1973, repaired (in some way) by Alan Pyne at 119 Dartford Road in the summer of 1977. The original drivers will have been Celestion Greenbacks. The amps normally paired with this cab were the JEI V100 and the JEI FR100 and AP100.
Thanks to Keith, pictures of AC100 serial number 1657, probably second quarter of 1966. Chassis number 01943. The choke has the date code "GW" = July 1965. Further pics on this page.
AC100 serial number 1657.
A detail of the circuit board of a "Jennings Electronic Industries" AC15 from late 1972 / early 1973. Note the printed legend: "TRIUMPH ELECTRONICS / PURLEY SURREY" followed by the Triumph mongram.
The JEI B50, O50, B100, O100, and the public address amplifiers, were also designed / manufactured by Triumph too - see the entry for 26th November on this page. Geoff Johnson, owner of the company, had produced a good deal of contract work for Tom (in JMI days) - from 1961-1967.
Quite how Triumph's work for JEI fitted in with that of APT Electronic Industries (of Ascot and Byfleet) is not fully clear at present. It may be that APT, which came into the picture in the summer of 1969, took over production of designs originally developed by Triumph - see this page (report published in July '69). Close inspection of the trace-side of other circuit boards will probably reveal more.
Just to add that the boards of the B50, O50, B100, O100, and PA amps, have component numbers printed on their upper face. Boards of other amps - the J40, J100, J200, AC15, AC30 - tend not to.
Trace side of the circuit board of a JEI AC15.
29th July (2)
Below, a couple of details from the JMI pricelist of Spring 1964 - compiled in advance of the Frankfurt Trade Fair, printed, though not necessarily circulated, in February. Note the presence of the AC100, available with a speaker cabinet, presumably the 2x15", and as amplifier section alone. 2x15" speaker cabinets were not offered separately at this point however.
As the list was being printed, Westrex were busy producing chassis. The latest component date code evident in the early amps is on the potentiometers: "AL" = January 1964. For the most part chassis are likely to have remained on shelves at JMI until orders came in. It is clear from survivals though that some were boxed up and made ready for sale in batches. It took quite a while for sales to get underway.
The Bank of England inflation calculator reckons that £195 in 1964 was equivalent to £2788 in today's money.
AC100 serial number 1414 from early to mid 1966. The speaker cabinet is from early 1968 or later though as can be seen by the solid state style logo and the Goodmans Audiom 81s with special Goodmans labels (for JMI). Similar labels can be found on certain Goodmans !8" drivers in Foundation Bass cabs sold by "Vox Sound Equipment Limited" (which took over unsold JMI stock in mid '68). Further pics can be found here.
AC100 serial numnber 1414.
Just a quick update to yesterday's entry. Two of the green TCC preamp filter caps have date code "WE" = May 1965, the third has "VL" = November '64. The main power section filters - made by Daly - have the latest codes in the amp: "WK" = October 1965.
One of the two 100uf/500v Daly filter caps, date code "WK" = October 1965.
Thanks to Steve, pictures of an AC100 mark 2 from the last third of 1965, chassis number 1685, a serial number probably in the high 1000s / low 1100s. Further pictures can be found here. Very few renewed components. The latest visible elements are the new-style "can" rectifier diodes. Up to this point Mullard top-hat rectifiers had been the norm.
In terms of date codes, the Welwyn 470R cement resistor at the speaker terminal has "WB" = February 1965, and one of the green TCC filter capacitors in the preamp has "WE" = May '65. The Mullard XF2s date from 1962 and 1963.
The Mullard-Amperex data sheets for the EL34 can now be found here.
Details of an MC100/6 public address amplifier (transistor preamp, valve power section) from late 1965 or early 1966, thanks to Mike. Note the blanked-off holes for a third set of bias pots - probably experimentation. It is highly unlikely that a second set of EL34s could be made to fit on the chassis.
Note also the single 8ohm and 15ohm speaker sockets - not exactly useful for a public address amp. Line source column speakers came in pairs, 16ohms apiece. The amp may have been designed for some special purpose. Its metal clad case was probably repainted relatively early on - deep turquoise (now worn) over the original hammertone silver.
The openings for the speaker sockets in the chassis have not been adjusted. The current jacks and escutcheons may be original - hard to tell though. If not, then the openings will certainly have had two pin Bulgin sockets.
Third set of holes, at right near the output transformer.
Coming shortly, a set of Mullard characteristic sheets for the EL34. These were assembled for Amperex and incorporated in a three-volume set of data books published in 1965.
The original Mullard sheets date from May and September 1957, and September 1960.
Thanks to Andy Barratt, a picture of the party/gathering at the Royston Industries head office (Hill Street, Mayfair) following the award to JMI of the Queen's Award in early April 1967.
From right to left: Eric Summer, chairman of Royston; unknown; Dave Clark, then recently appointed roving ambassador for JMI; Reg Clark, General Sales Manager; Dick Denney; Cyril Windiate, Tom Jennings's deputy; Tom; Joan Jennings (?), Tom's wife; Colin Barratt, Overseas Sales Manager and Andy's father; Charlie Cobbett; JMI's Group Liaison Officer; and far left, unknown, though somehow familiar.
In the background, a Vox Supreme amplifier. Dick was photographed playing his Vox New Escort Special guitar in front of this, and in another shot, posing with Dave Clark, also a Dartford lad.
A page on JMI and the Queen's Award can be found here on the Vox Supreme website.
A couple of things in relation to early Vox Metal-Clad Public Address amplifiers. The first is that Triumph Electronics, the contractor responsible for building and assembling the units for JMI, produced batches of preamps first, then made up power sections to order. Illustrative pictures to follow. Just to say for the time being that the preamps for the MC30, MC50 and MC100 were identical.
The second thing is that the MC100 seen on stage with The Who in mid 1965 had evidently been assembled or rather re-assembled incorrectly. Note that Pepe Rush recalls servicing a Who PA unit in his Soho workshop. The reference can be found at the foot of this page.
In the picture below one can see that the preamp section has been mounted *behind* the uprights at the front of the case. These uprights are 1" wide (measured from the case sides) and extend the full height of the front. Normal factory practice was to mount preamp sections in front of these uprights.
26th June (2)
Some notes on "Jennings Electronic Developments" pedals. Immediately below, a leaflet outlining the range with the "Rotosound" emblem at top. Were the pedals made by Rotosound and sold by Jennings or simply rebranded by the former?
Dick Denney and James How were wartime buddies - a musical duo, Dick playing guitar in the style of Django Reinhardt, James on violin in the manner of Stephan Grapelli. How agreed to be Tom's distributor in late August 1968. The Rotosound factory was in Bexleyheath, only a short step away from Tom and Dick at 117-119 Dartford Road.
Below, a detail from a picture published in the music trade press in December 1968. A copy is also on the Rotosound website, but dated too early. The location is the Rotosound shop on Denmark Street. James How is at left (out of view in this detail), and Alan Marcuson with pedal in hand, at right. The pedal is a rotary Jennings pedal - either a "Growler" or "Repeater" with twin switches at one end and the pedal pad at the other.
Detail from a picture printed as part of a full-page Rotosound advert in December 1968.
For Rotosound and the Jennings Fuzz pedal, see Nick Steenburg's superb page on his fuzzboxes.org site.
A line at the foot of the back page of the leaflet indicates that two patents had been applied for in relation to the pedals. At present, the numbers printed have not led anywhere relevant in the old Patent Office records. The search continues.
Below, a review of the Jennings Electronic Industries display at the Russell Hotel Trade Fair, August 1969. A couple of things worth highlighting: (1) the K1 keyboard does not appear to found its way into general production. This is the only image that has come to light to date. (2) The Attack Percussion unit, for which a full-page advert was taken out in September 1969 (on this page, is said to be subject to world patents. The text of the review was repeated without the illustration of the K1 in "Melody Maker" magazine.
As for the patent or patent-applied for number mentioned in relation to the Attack Percussion, none seems to have been printed in any of the obvious places. Perhaps one will eventually come to light.
In August 1969, the "Jennings Electronic Industries" J68 and J69 portable organs were introduced to the public and music trade for the first time at the Russell Hotel Trade Fair - the J68 a two manual; the J69 a three manual, the first portable instrument of its kind, which caused quite a stir. The two models were fairly short lived however. By August 1970, the J70 and J71 - their successors - had been introduced.
August 1970. The J72, a console version of the J70, followed in August 1971.
Jennings J70, two manual.
Jennings J70, detail of the drawbars.
In April 1971, Tom moved to patent the drawbar system - effectively paired sliding potentiometers in a protective assembly - registering the design with four photos.
April 1971. Copyright of the design expired at the end of March 1976 and was not renewed.
Some notes on the size (sizes) of Vox Metal Clad public address amplifiers, given in inches.
From mid 1964 to Spring 1965, the four-input all-valve amps had a square "footprint". The MC30/4, MC50/4 and MC100/4 all came in a case of the same size. The MC15/4 was slightly smaller.
MC15/4: 12" x 12" x 4 5/8".
MC30/4, MC50/4, and MC100/4 14" x 14" x 7 1/8".
The six-input hybrid MC50/6 and MC100/6 (solid state preamp, valve power section) were rectangular in format:
MC50/6 and MC100/6 21 3/4" x 11 1/2" x 9 1/2".
In mid 1965, the two lines were revised and the formats of the cases changed. The details below relate solely to the MC50s and MC100s. No definitive information exists at present for MC15s and MC30s.
The four-input MC50/4 and MC100/4 came in a case of the same size:
MC50/4 and MC100/4: 14" x 17" x 7 1/2".
The six-input MC100/6 came in a case of a fairly fixed format. The MC50/6 on the other hand came in two different sizes, one as the MC100/6 the other less deep.
MC100/6: 20" x 14" x 9 1/2".
MC50/6: 20" x 14" x 9 1/2".
MC50/6 (smaller): 20" x 12" x 9 1/2".
From 1964 to 1966, main metal case bodies were finished in "hammertone" - what we would call "hammerite" today. Surrounds at front for the preamp were black. From 1966, the main bodies were occasionally finished in black too.
A detail of a pic of The Who taken at the New Palladium Ballroom, Greenock, 8th May, 1965. Pete Townsend's AC100 speaker cabinet is the first type - parallel bars close together and (doubtless) a "basket" on top for the amp to sit in.
Photo: W. McGowan and F. Quin.
There is now a new page on the Vox Supreme website on the "Vox Sound Equipment Limited" display at the Russell Hotel Trade Fair, August 1968, the first public outing for the new company.
Below, one of two pictures of the VSEL rooms published in the music trade press:
The organ room - 134a (?) - on the first floor of the hotel. In view, a Riviera and Super Continental organ, and two Gyrotone IIIs, one with an AC30 Super Twin amplifier section on top.
Among the new items unveiled at the Fair were the plug-in booster units made for Vox by JEN Elettronica (see yesterday's entry for more on JEN). These are listed in the VSEL pricelist of 1969.
Below, a detail of the boosters from the catalogue ("Der Sound Macht's") printed for the German market in mid 1969:
Boosters produced by JEN for VSEL.
Tom Jennings's distribution deal with Kustom (see below, entry for the 31st May) was not his first. Evidence has just come to light to show that he was making arrangements to distibute JEN pedals in February 1968.
JEN Elettronica (based in Pescara) was set up by Joe Benaron and Ennio Uncini in late 1967, initially to assemble certain Thomas Organ pedals along with other designs and types marketed by other companies. Tom and Joe were old partners.
Although this is not the place to enter into matters of documentation, it should be said that as ever there is quite a lot of twaddle on the internet surrounding JEN.
The site that has consistently offered good information (and pointed in the right direction) over the years is the "Big Muff" history site - but some corrections are evidently needed to the narrative as set out there.
Below, one of the first JEN adverts placed in the popular British music press - September 1968. Note that there is no mention of Jennings. Equally there is no mention of JEN in Tom's catalogues of late 1968 and 1969. More on this shortly.
In early 1970, "Vox Sound Limited" began marketing JEN pedals and effects under its own name (as other companies did under theirs). This will be taken up on the Vox Supreme website.
6th June (3)
The page on the Jennings AC100, link below, has now been updated. A page has also been begun on the Tympano range, late 1968 to autumn 1973 - available here.
6th June (2)
Thanks to Cedric, pictures of Jennings AC100 serial number 2031, early 1973. The numerical sequence began at 2000. Although no published note of its introduction has come to light so far, a picture printed in the trade press shows that an AC100 was certainly on show at the Russell Hotel Trade Fair, August 1972. Whether the model was exhibited in some form in the Jennings displays at Frankfurt in February and Chicago in June is unknown.
The earliest JEI AC100s had silver control panels, later ones black. The page on the JEI AC100 will be revised and updated shortly.
Dick Denney in C&W finery at the Jennings stand, August 1972 (picture published in September). There was a definite "Wild West" theme to some of Jennings's adverts and guitars.
Thanks to Oliver, pictures of a pair of Jennings T.1 Tympani, probably from c. 1969-1970. Brought to market in late 1968, the T.1 was also sold by Rotosound with a Rotosound badge. The speakers are 10" units.
Detail from the "Jennings Electronic Developments" catalogue prepared shortly before the Frankfurt Trade Fair of February 1969. There were four models of Tympano in total.
At present this rather smudgy newsprint pic is the earliest firmly dated photo of Vox equipment in a dealer's shop in the USA - 8th December, 1964, Hal Morris Music Mart, Lansing, Illinois.
Equipment was air-freighted by JMI to Chicago and Sepulveda initially, Thomas Organ distributed from there. The Thomas distribution centres in the Chicago area were the storage facility in Evanston, and the "Studio" in the "Golf Mill Center" at Niles.
Hal Morris still had the Vox T60 - or at least a T60 - in March 1965.