Vox AC80/100 (early AC100) serial number 173

VOX AC100 - UPDATES AND NEW INFO

2024

12th April

A shot of the preamp of from Jim Elyea's book. There are two things of note: (1) the grey 0.05mfd Radiospares "snubber" capacitor over the mains switch. These were fitted at factory to many AC100s and AC50s produced with a view to export to the USA. The option of the cap. was never registered in circuit diagrams.

(2) the English-made Daly capacitor at the right-hand end of the tagboard has the date code "WE" = May 1965. Perhaps one of the spare/replacement components supplied to Thomas Organ by JMI?

That the amp was in California by April '65 seems clear: a photo of it appears in the first issue of Thomas Organ's "Teen Beat" magazine, printed while Marv Kaiser's first Vox "Battle of the Bands" competition was still in progress (see the page linked above).

AC100 serial number 225.

Detail. "WE" is May 1965. Solder joints look old.

Whether serial number 225 travelled with number 226 is unknown: but the latter was certainly produced for use in the USA too.

Detail of serial number 226, the 0.05mfd Radiospares cap visible top right.

AC100 serial number 392, also fitted at factory with the 0.05mfd Radiospares snubber.

8th April

Below, the wiring schema of the upper compartment of the AC100 SDL speaker cabinet (with basket top trolley) from early 1965. Total impedance 15/16 ohms. The lower compartment is arranged similarly. The two were wired in parallel at the input socket, resulting in a total impedance of 8 ohms for the cabinet as a whole.

Wiring schema of the upper compartment of the AC100 SDL speaker cabinet (with basket-top trolley) from early 1965, date codes on the speakers mid December 1964.

Each compartment has a pair of 1uf capacitors, wired in parallel for a total of 2uf - to protect the Goodmans Midax horns from potentially damaging low frequencies.

Detail of the upper compartment of the SDL cab, early 1965.

The wiring scheme adopted for this cab (and at least one other) was actually the second adopted by JMI. The first scheme, used in the first five (certainly) or six cabs, is entirely different, the two pairs of capacitors being mounted together in the lower compartment. Below, a detail from a photo of one of the cabs issued to the The Beatles in mid August 1964.

Detail from a photo of one the SDL cabs issued to the Beatles.

Four of the five cabinets that have this first wiring scheme were made together: two for the Beatles; and two for loans and demonstrations. These last were lent out by JMI for short stints to various bands for key performances, live and filmed, and exhibited at trade fairs and other events. Reg Clark, JMI's General Sales Manager, is seen with one, for instance, at the Russell Hotel Fair, late August (ie. while the Beatles were away in America).

A fifth was made a little later - at some point in November. This went out on loan in the UK in December, and was then shipped to the USA, also to serve as a loans and demonstrations unit - .

7th April

A rudimentary schema of an AC100 on top of a trolley with parallel bars (as from above). The position of the amp's feet are marked in red. As can be seen they straddle the trolley rather than slotting in between front and rear bars, which in many respects would be a more logical arrangement.

That an amp might accidentally be tugged backwards would probably be an extremely rare occurence though. Most of the weight of the amp (the transformers) in any case is towards the front.

The schema represented is based on AC100 SDL serial number 392. The amplifier section cabinets of serial numbers 262, 328, and 337 have feet in identical positions.

Not to scale. Based on AC100 SDL serial number 392. The (tubular) bars of the trolley are 7/8" in diameter. Note that the feet, which are shallow, locate against the curve of the bars. The width given for the centre section of the trolley top - 16 1/2" - is the total distance from outermost edge of one tube to the other.

Detail of AC100 SDL serial number 392, mid 1965 (speakers dated May '65), parallel bars across the top of the trolley.

6th April

Further slightly random notes on early AC100 SDL speaker cabinets and trolleys.

(i) Early speaker cabs (late 1964 and early 1965) were of the same size as later ones (mid 1965 to 1968): 40" tall; 11 1/2" deep; and between 27" and 27 1/4" wide.

(ii) The distance from outer edge to outer edge of the parallel bars immediately below and above the handwheel of early basket-top trolleys is 6 3/4". Later trolleys: 9".

Side bars of one of the second generation basket-top trolleys, the cab tilting back (so piping sloping).

(iii) The AC100 amplifier sections that were sent out with AC100 SDL speaker cabs normally (as a matter of course) had black cloth. Very few amps in thin-edged boxes were done out in black.

(iv) AC100 amplifier sections were regularly fitted with feet (small furniture glides) that do fit as logically as one might expect on trolley tops. More to follow on this. Below, a picture of the AC100 used by Lennon, Belfast, 2nd November, 1964. The amplifier section was not the one he normally had. Its feet (furniture glides) do not slot properly into the basket top.

Belfast, 2nd Nov., 1964, the feet on the right-hand side amp sit on the bars, not inside the basket top. The amp was probably a spare, less likely borrowed from one of the other bands on the package tour.

Serial number 178 is similarly lop-sided when placed on top of a basket trolley: the only way to position the amp is with two feet within the top, the other two sitting on the bar.

5th April

As mentioned yesterday, AC100 SDL serial number 236 (black panel, cathode biased) is the earliest surviving instance currently known of a trolley with parallel bars on top - in other words a standard "Mark 2" trolley. That the speaker cabinet is an early one is clear from the position of the XLR socket, the wiring evidently feeding to it from the upper compartment of the cabinet. A little later on, the wiring pattern of the SDL cabs was changed, the XLR socket repositioned lower down the middle back board so the wires could feed to it from the lower compartment.

AC100 SDL serial number 236. XLR socket relatively high up on the back board, indicating that the wiring to it issues from the upper compartment of the cabinet. The original speakers have unfortunately gone, but the original wiring loom is evidently still in place.

It is likely that most of the SDL cabs that were sold with black panel AC100s had cabs of the type illustrated above.

Below, a slightly later cab in need (as pictured) of some attention. The speakers have been out and put back in rather haphazardly, but key portions of the wiring loom are intact. Note the presence of the green capacitor positioned to the front of the compartment, as in two of the early cabs with basket-top trolleys. In the case of the cab below, however, the wiring that leads to the XLR stems from the lower compartment.

Possibly a replacement trolley from an American Super Beatle - note the castors (of the type normally found on Thomas Organ-made trolleys).

The lower compartment of one of the cabs with a basket-top trolley, early 1965. The wires leading to the XLR socket issue from the upper compartment (just visible at the top of the pic.)

By mid 1965, JMI introduced a further change: instead of the paired green 1uf capacitors, a single larger-bodied 2uf capacitor painted black and positioned further back in the cabinet.

Speaker cabinet of AC100 serial number 392, picture showing the position of the new (relatively) type of 2uf capacitor (made by TCC but painted black by JMI). The speakers in this cabinet have mid May 1965 date codes.

4th April

To return to trolleys: note 4) standard later JMI AC100 SDL trolleys (certainly in production by February 1965).

In contrast to early basket-top trolleys, later "standard" JMI trolleys were made out of 7/8" diameter tubing all round, the frame consisting of three (rather than two) sections that slotted together: the base (with wheels), and two side pieces that contained the locating points for the cabinet swivel mounts and half each of the top. These side pieces slotted into the base and into each other at top.

Early basket-top trolleys came in two sections: the base and a single section comprising of sides and top.

Detail of AC100 SDL serial number 392, mid 1965 (speakers dated May '65), parallel bars across the top of the trolley.

Below, a picture of an American Super Beatle trolley, wheels removed and part dismantled to show the three principal elements. In overall form, these trolleys were copies of JMI's AC100 SDL trolleys, though there are significant differences in detail.

American Super Beatle trolley to show the three main elements. JMI AC100 SDL trolleys had the same tri-partite form, and identical dimensions. Areas of difference: the type of castors used, the swivel mount, the intermediate bars on top; mode of production. The trolley pictured above was flown about the USA in the 1970s by "Consolidated Airlines" (transit labels still sellotaped on upper and lower sections).

The earliest dated instance of a new-style JMI trolley? - February 1965 in a short film clip shot at Dartford Road. The earliest instance currently known in terms of surviving amps? - AC100 serial number 236. More on the early black panel amps tomorrow.

3rd April

Just to record (as material gathers) an analogy for the thickness of the early AC100 trolley side mounts: the Line Source 40 (LS40) public address column tilt-back stands.

Early AC100 SDL side mount, detail showing the thickness of the metal ring into which the mount on the cabinet slots. In between the two, a brown phenolic ring.

One arm of a Line Source 40 tilt-back stand, the cup at the end of similar thickness to the AC100's trolley mount.

Whether other early amplifier trolleys had similarly substantial swivel mounts is not known for certain at present - but the likelihood is strong one. Below, an AC50 trolley (sometimes called a Mark 3) with basket top from early 1965, the diameter of its tubing along the lines of the early AC100 SDLs: lower section 7/8"; upper section 3/4".

These trolleys were supplied with late single-channel diamond-input AC50s and early large box AC50s - from late 1964 into early 1965.

2nd April

A rare instance of a "Jennings Electronic Industries" circuit diagram, the page below part of a set of five for the 100W Public Address amp with reverb. The sheets were drawn by Albert (Bert) Hogben, who had worked for Tom in JMI days.

A xerox made some time ago from a spiral-bound collection. The set is dated 4th December 1973.

1st April

Picking up from yesterday's entry: note 2) The swivel mounting hardware of the early basket-top AC100 SDL trolleys.

Again, the format is different from the one later adopted by JMI for its standard AC100 trolleys. The handwheel face is engraved rather than pressed, the logo defined by bounding lines rather than fully recessed letters. This can also be seen in the photograph submitted by JMI to the Old Patent Office in October 1964.

Handwheel face, basket-top cab.

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Detail from the photo of the AC100 SDL registered by JMI with the Old Patent Office in October 1964. The logo is "blued" out to indicate that the name was not part of the application. "VOX" had already been trademarked by Tom in the 1950s.

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Handwheel inside face.

Forming part of the structure of the trolley frame is a sizeable hoop that locates over the "castle" style cabinet mount. Between the two, a brown phenolic ring (second photo below). The standard later JMI format .

A circulat metal plate (not shown) goes between the trolley mount and the handwheel.

More to come on the early trolleys in a coming post.

31st March

The first of a series of notes - eventually to be gathered together on a page of their own - on early AC100 SDL trolleys with basket tops.

1) The lower section of the trolley (the wheeled base unit). Both early on, and later, these were made of tubing with a diameter of 7/8". The early trolleys (with basket tops) were less broad, however, than later ones:

BASKET-TOP TROLLEY

Total width of whole - 29 1/4".

Inner width (between bars) - 27 1/2".

Total depth of base - 14 7/8".

LATER JMI TROLLEYS (and Thomas Organ Super Beatle trolleys). PARALLEL BARS ON TOP.

Total width of whole - 31 5/8".

Inner width (between bars) - 29 7/8".

Total depth of base - 15".

As the 4 x 12" cabinets were 27" wide, tolerances in the early trolleys were really tight - only 27 1/2" between the uprights.

Early basket-top trolley (early 1965).

30th March

Thanks to Jack, pictures of AC100 serial number 868, late 1965, .

AC100 serial number 868.

23rd March

Thanks to Joe, pictures of JEI Ac15 serial number 3086 have now been added .

13th March

Some notes coming on early AC100 SDL trolleys. For the time being, a quick picture of the base of one, the insert designed for Kenrick Shepherd ball castors with a threaded stem, 5/16", British Standard Whitworth. More to come soon.

10th March

Thanks to Joe, pictures of a handsome early Jennings AC100 have been .

27nd February

A further possible identification: - serial number 206, currently in Denmark, is probably the amp used by the Swinging Blue Jeans in Sweden in mid October 1964. Again, compare the alignment of diamonds on the grille cloth.

22nd February

The amp on the left is probably serial number 184. There is a strong chance that it was the one used by Gerry and the Pacemakers for their set on the T.A.M.I Show, Santa Monica, 28th-29th October, 1964. Note the distinctive stretched grille cloth and alignment of diamonds. The speaker cabinets are probably the same too.

31st January

Thanks to Luca, pics of AC100 serial number 291, black panel, early 1965. In terms of the balance of sales, it seems increasingly clear that the majority of AC100s with black panels went to Europe or were sold locally in the UK. That is not to say of course that batches did not also go to the USA. Numbers 231, 236, 256, and 262 appear to have had long histories there.

17th January

Thanks to Oly, a shot of the interior of the Vox MC15/4 from the autumn of 1964 - preamp assembly at top, power section at bottom, the two linked via umbilical wiring and an octal connector.

Further shots to come soon.

Vox Metal Clad 15/4.

11th January

Just to signal that a further has come to light - one of three now known, two with their original serial number plates (numbers 1003 and 1007), this one without. Thanks to Ray for info on the amp.

7th January

A short piece in the American music press, November 1964, signalling again that Thomas Organ was the exclusive distributor of Vox in the USA and that distribution and the awarding of franchises were underway.

Batches of equipment had arrived as far back as the 17th September (announced in the Chicago newspapers). See . But the amplifiers - and presumably guitars too - will have spent some time in the Thomas Service Center in Evanston - in the case of the amps, for testing and checking, the resetting of voltage selectors, and the recording of salient details (type, model, serial number and so on) in the Thomas log books.

The same will have been done for the batches flown (slightly later on) to Van Nuys for Sepulveda.

American music press, November 1964.

2023

31st December

Just to add in relation to the JEI Echo, its dimensions are (case only, excluding protrusion of feet and handle): 13 3/4" wide, 6 3/8" tall, 9 3/4" deep - in other words, around an inch larger in all three dimensions than the latching top (and front) case of the Vox Domino Echo of 1964. The latter was of course valve rather than transistor.

29th December

Some pictures of JEI Echo unit number 1047, probably late 1974 / early 1975. The circuit board is designated "pc 176 i.c.", "i.c." standing for integrated circuit. Component date codes, insofar as any can be seen on the tightly packed PCB, are of 1973.

Mains transformer and motor at left; tensioning arm at right.

The solder points of the integrated circuit chip.

15th December

To note for the time being that serial number 836 has recently come to light in the USA. The chassis appears to have a heat shield around the EL34s, though, first seen normally on the chassis of amps with numbers in the 1100s. There are no pictures of the electronics at present. Thanks to Chris for signalling the amp's existence.

11th December

Featured on all recordings by "The Manatees" from 2016, Jennings AC40 serial number 1230, probably produced (ready for sale) in early 1972. Thanks to Tyler Bloor for the pictures. A couple more pics can be seen on this page.

JEI AC40 serial number 1230.

9th December

A superb AC100 speaker cabinet recemtly come to light: trolley with basket top, second generation/format wiring, probably complete in all respects early in 1965, still in the UK. Further pictures . Thanks to the owner for the pictures.

6th December

Thanks to Nick, the note published in the American music press in March 1968 of the formation of Tom Jennings's new company - "Jennings Electronic Developments" - following his dismissal from JMI.

The page on the events of 1967 and 1968 .

March 1968.

5th December

A new page has now been set up for the illustrated in the entries below. Further pics to be added in due course.

4th December

A couple of shots of the power section of the MC100/4, electrolytics evidently replaced a few years ago. The bias network differs in a couple of respects from the network in the other MC100/4 with a discrete bias board.

The rectangular opening in the rear lip is for the bolt attaching the section to the metal case.

The date code on the Mullard mustards is "C4N" = third quarter of 1964.

3rd December

The rear panel of the MC100/4 - standard terminal block (from factory) for speaker connections rather than the Belling Lee L1469 strips used on these amps from Spring 1965. See the entries for 12th and 20th January at the foot of this page.

Rear panel.

Rear of the front panel showing the lines from the output transformer to the terminal block. Orange grommets are always a good sign of assembly by Triumph.

The amp below, similar in date to the one above and also in the UK, was evidently prepared in much the same way:

2nd December

A note on the transformers used in the Vox MC100 amplifiers. These were massive open-frame units, probably made for JMI by Drake. The lamination stack of the mains unit for the MC100/4 measures: 5 1/4" x 4 1/4" x 3". The output transformer's stack measures: 5 1/4" x 4 1/4" x 2".

The designations on paper slips are "D45M/1" (mains) and "D55 O/1" (output). The choke is unmarked.

Upper chassis, power section.

Mains transformer sticker.

Output transformer sticker

1st December

Coming shortly, a set of pictures of a further early flat-fronted MC100/4 recently come to light, one of four currently known.

The latest component date codes found so far: Mullard mustard capacitors in both preamp and power section "C4N" = third quarter of 1964. In company with another early example, a number of the bias components are on a discrete tag-board. During the course of 1965 a single board was introduced for the main power circuitry.

Assembled by Triumph Electronics for JMI under contract. The carry handles are probably early additions, the DIN socket on the front later. The amp was until recently still in use in Germany.

29th November

It is worth recording that the advert below, often reproduced without much comment, is one of the first, if not the first, full-page promotion placed by Thomas Organ for Vox in the American music trade press - February 1965. Dealers were the intended audience. The chance to cash in was the message.

It took Thomas a good while to break away from its "British Invasion" theme and branch out into something more interesting. From late 1966 / early 1967 the company really began to find its feet though, producing innovative and colourful promotional material based around American bands.

February 1965. The photographs used by Thomas in its early promotions were often a year old or more.

28th November

American music press, October 1964 - a nice shot of Tom and Joe Benaron, perspex AC30 and Continental in front, Russell Hotel Trade Fair, late August 1964. The official "handshake" photo for the "Million Dollar Deal" had already been published in the British music press in September.

October 1964

The deal was not in actual fact to distribute "all" Vox products, simply an agreed selection. More on Vox in the USA in 1964 and early 1965 to follow soon.

27th November

It turns out that the "Jennings News" brochure was printed in two versions - one in late 1969, the other in late 1970. Front page and main content are identical. The back pages are different however.

The version issued in 1969 ends with electronic percussion and an advert for the Jennings repair service. The version rejigged in 1970 ends with the AC40 - displayed for the first time in the UK at the Russell Hotel Trade Fair - and the Tympano units, no more Tamborino.

Back page of the 1969 printing.

Back page of the 1970 printing.

23rd November

Thanks to James, a couple of provisional pictures of "Jennings Electronic Industries" Echo unit serial number 147, late 1974 or early 1975, recently sold, further shots to come. Two other examples are currently known - numbers 145 and 148 - .

22nd November

April 1964, the first full-page advert seeking a country-wide distributor placed by Jennings in the American music press. A small image of this page was posted years ago on one of the bulletin boards (now long gone - probably the Plexi Palace site) - good now to have the source and date of this printing. It is likely that there were at least two other printings in other journals.

April 1964.

21st November

March 1964: the beginning of Tom Jennings's search for a country-wide distributor for Vox in the USA - a sort of direct/indirect report, published in the American music press along with the "Jumping Beatles" advert below.

American music press, March 1964.

American music press, March 1964. The success in the USA was of course the appearances on the Ed Sullivan show and the concert in Washington.

The various versions of the advert published in the UK can be found .

18th November

Thanks to Nick, a detail from a full-page advert placed by Jennings in a spread of American music trade magazines to coincide with the . The Continental at this time was the big thing - a version of the ad printed in various British and American journals a few months earlier gave the specifications in some detail.

The American material from 1963 relating to the Continental will be posted in its entirety on the Vox AC30 website in due course.

5th November

The amplifier section box of AC100 serial 231 survives in the USA, the chassis - either copper or black panel - presumably long gone. That the grille cloth on the box is black suggests that the amplifier was issued as part of a SDL set. There are at present no details bearing upon the question of when the box (and/or amp) found its way to America however.

AC100 serial number 231 (box only).

1st November

The page on the has been updated with further examples. Thanks to James for pictures of serial number 986, close to the end of the run. The highest number encountered so far is serial number 990, made ready for sale in the summer of 1974 - old stock finally finding its way into the world.

23rd October

September 1962, a detail from a Selmer advert for the Meazzi Factotum, a sort of multi-purpose amplifier (with echo and reverb) and speaker set. The Factotum was well known to Jennings, which also imported units for sale - one offered by Musicland in 1963, circuit diagram copied in August 1960 (for factory use).

The thing of note in the advert though is the tilt-back column speakers - a good nine months before JMI began work on its Line Source 40 columns. The Meazzi/Selmer speakers were clearly the inspiration. The hand-wheel assembly took a little while to work out however - .

September 1962.

15th October

Below, a shot of the plate of AC100 serial number 1848, which survives in Spain. No further details at present. Thanks to Alfredo for the pic.

1st October

Just to note that AC100 serial number 2025 and its 2x15" cabinet is currently for sale in the Netherlands. Pics to follow. Thanks to Eric for the info.

23rd September

Thin-edged AC80/100s with black grille cloth (from factory). These were always paired with speaker cabinets with black grille cloth. At present four, perhaps five, are known from photos. The amps issued: to John and George of The Beatles in late July 1964; to Paul McCartney in early October; to Brian Jones in mid October for the Stones' brief European tour; and (possibly) to the Hollies in mid September 1964 (for use with a large box AC50 cabinet).

Perhaps only around half a dozen made in total? JMI AC100 Super de Luxe speaker cabinets generally went out on loan in late 1964 with AC80/100s in thick edged boxes. These naturally had black cloth too.

The cloth on serial number 169 is likely to have been replaced later (the diamonds are too large for 1964). Another surviving amp once had black cloth, but it is not known whether this was from factory. Very probably, but no absolute proof.

Thin-edged AC80/100s with brown grille cloth were invariably used with Foundation Bass or 2 x 15" speaker cabinets also in brown.

19th September

A note on the initial batch of four AC100 Super De Luxe speaker cabinets made in early August 1964. Two of the four were issued to The Beatles and paired with the amplifier sections in thin-edged boxes that had originally been given by JMI to John and George in late July. The other two - sets with new amplifier sections - were retained by JMI for promotional purposes. Info that has come to light recently shows conclusively that the amplifier section of at least one of these promotional sets was housed in a thick-edged box with plastic corner protectors - the earliest instance for an AC100 to date. This was the AC100 Super de Luxe that JMI had photographed for its submission to the Patent Office (October 1964).

More to follow in due course. The other Super de Luxe set retained by JMI was mainly used for loans and is seen on stage at various events from mid October to December 1964. In late 1964 a new batch of AC100 Super de Luxes was produced, some again for loan and demonstration purposes, others for sale.

15th September

Also started on the page on "Musicland", a section on sheet music.

14th September

Added to the page on , the Jennings shop in Bexleyheath, pics of the envelope and return envelope of a catalogue set sent out to a prospective customer in February 1964.

Later envelopes were printed with the silhouette of the "Jumping Beatles" rather than that of "The Shadows".

12th September

August 1962, part of a double-page advert placed by Tom in the music trade press to accompany the JMI stand at the Russell Hotel Trade Fair - the "Piano-Harp", a means of reproducing the effect of a honky-tonk or "tack" piano (and other instruments) on any normal upright piano.

Jennings had been made exclusive UK distributor of the device, also of the "Piano-Hush", by "Piano Accessories Incorporated" of New York. Quite how Jennings and Piano Accessories came to link up is not known at present. It should be said however that Tom had done business with other American companies - notably Excelsior of New York - from as early as 1950.

The first formal showing by JMI of its own range in America was at the NAMM show in the summer of 1963 - see the entry below.

The "Piano-Harp" and "Piano-Hush" remained part of the Jennings catalogue through to the end of 1965. That a full page advert was taken out in 1962 tends to indicate that Tom attached more than ordinary importance to the devices and the deal.

August 1962.

An advert placed by "Piano Accessories Inc" in an American trade magazine, March 1961.

JMI pricelist, November 1965.

4th September

A couple of items relating to Tom's first major foray into the USA in the 1960s - the Jennings stand at the NAMM show in Chicago, July 1963. The first is a note of the presence of the stand in an American music trade journal - Room 966W of the Palmer House Hotel. Although listings for the show are by no means comprehensive, it is evident that Jennings was there independently at this point. The arrangement to distribute Thomas Organs (announced in August 1963) had not yet been broached or at least finalised. Close to Jennings on its corridor were V.C. Squier Company Incorporated (violins and strings) in Room 968W, and Mills Music Incorporated (music publishing) in Room 969W. Thomas had rooms 617-620 on another floor.

The page on JMI's stand at the Chicago show of 1963 .

The second piece is a note of the application by Jennings to protect the trade name "VOX" in the USA, filed in October 1963, perhaps at the suggestion of Joe Benaron, who managed Thomas. Joe attended the Russell Hotel Trade Fair in London in late August 1963.

American music trade journal, July 1963.

US Patent Office application.

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