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Vox AC30 website updates

August 2023

24th August

A brief synopsis of the types of instruments stocked in December 1962 by "Musicland", the Jennings shop in Bexleyheath. There is a new page on the shop on the Vox AC100 website. Note the mention of "Vox Transistor Organs" - which must be the Continental - the earliest dated instance so far after the ads in Melody Maker (which can be seen here).

December 1962

23rd August

Some random notes on Elac speakers (for AC10s and Line Source 40 speaker columns). A synopsis of the various elements mentioned below will be added in due course to the page on Elacs.

Cones: - either made by Pulsonic, stamped in white with a code along the lines of "xx/434/001" (there are variations); or by Kurt Mueller, stamped "1469" followed by three letters. Pulsonics are by far the most common. It should also be said that cones were often stamped with large double digit numbers ranging from 11-16.

Cork gaskets: - normally stamped with the model number and a five digit numerical code which may be the date code. Occasionally the five digit sequence was stamped on the frame (particularly on certain blue Elacs produced for Jennings).

Frames: - stamped with a four digit number. No recognisable pattern has emerged so far, except that "8461" seems to have been the standard number for silver Elacs for Jennings (both the 10N/85 and the 10N/86). Many silvers have no stamped number though, the code perhaps having been overpainted with the silver/grey hammertone finish.

Silver Elacs: - as has already been noted - entry below for 11th August - these were evidently commissioned by Jennings in mid 1964. The early 10N/85 (15 ohms), which superceded the blue 10N/81, had a "tin can" type magnet (much as its predecessor's). Shortly thereafter, "bells" with rounded ends were supplied. It is evident that the 10N/86 (3-4 ohms), which superceded the blue 10N/82, followed the same path. Below, pictures of a set of four early silver 10N/86s in a Vox Line Source 40 public address column.

Early 10N/86 with "tin-can" style drum.

22nd August (2)

The first of a series on short notes on AC10s. The speakers fitted in AC10 Twins were generally 15-16 ohms apiece and wired in parallel for a total impedance of 7-8 ohms. Wiring at first was green and yellow, tightly twisted. This was achieved by clamping one set of ends in a vice, the other in a hand brace (drill), and winding the runs tight. From around serial number 1100, red and black wiring was introduced, less tightly wound. Red and black became the norm at least for silver Elacs, through to the end of the run. Thanks to Glen L. for signalling some slips on the main AC10 pages. Note that for the time being one must speak of "generally" and "the norm". Very occasionally it looks as though pairs of Elac 10N/86s (3-4 ohms apiece) were fitted, wired in series. These instances are to be distinguished from the use of Elacs pillaged from Vox Line Source 40 speaker columns as replacements for blown originals.

22nd August

Thanks to Pete, pictures of AC30 Super Twin, sloped sided cabinet, have been added here. The latest component date codes in the chassis are those of the Woden transformers - "KV" = October 1964. The amp as a whole was probably only ready for sale however in late 1965.

AC30 Super Twin serial number 4831 was sold in January 1966. Both amps evidently escaped the fire at the Vox Works in early December 1965.

AC30 Super Twin serial number 4788.

21st August

Thanks to Stefan and Jürgen, AC30 Twin serial numbers 21608TB and 21694TB are now known to exist in Germany. The European export market was still strong for JMI in late 1966 / early 1967 (and remained so throughout 1967).

Serial number 21608TB.

Serial number 21694TB; chassis number 13448.

18th August (2)

A note added - on this page - on machine stamped serial number plates on AC10 Twins. These began so far as one can tell at 3000. Machine stamped plates for AC100s - simply to give a parallel - are likely to have been kicked off at 300.

The question of how long the gap was between the manufacture of the AC10 plates and their actual use is best left open for the moment.

Detail of the plate of AC10/T - the "T" for Twin - serial number 3053.

It is worth saying that from number 3000, the sequence began to duplicate the one adopted for AC10s in 1958. Those "3000s" will have had hand stamped plates however. The "/T" not only served as a key identifier for JMI's despatch log books (which recorded date, destination, name of dealer / buyer, and so on), but a potential help in service calls. When asked (over the phone) how the amp was designated on the serial number plate, the amp's owner would reveal that it was a Twin instantly.

18th August

A few updates in relation to AC10s. Entries for serial numbers 4221 and 4222 have now been added to the page on early Twins.

Number 4221 was illustrated in the "Vintage Vox Calendar 2000" and probably formed part of the collection assembled by Reitz Promotions, a hire company based in Hamburg which provided a number of later 1960s amplifiers to accompany Wolfie's guitars. Reitz sold its amplifiers to the "Guitar Center" in the early 2010s. They were subsequently distributed for sale to various branches across the USA.

The chassis number of AC10 Twin serial number 2787, when last sold, was reported as being 2426 it turns out. The estimate of the number of chassis assembled by Burndept Electronics can therefore be narrowed: from 1425 (at least) to around 1500 units.

So far it seems that all Burndept-made AC10 chassis had grey control panels, production presumably kicking off at around the time that JMI got things going at the new Works in Erith in late 1964. Burndept, which owned the building (and leased it to JMI), had assembly rooms on its first floor. This type of "integration" was all part of the plan formulated by Royston Industries, the company that that had taken controlling interests not only in Burndept (from 1960) and JMI (from Jan. 1963), but also Heslop and Company, which went on to make cabinets for the latter: - the enabling of its subsiduaries to work together in what these days would be called an "ecosphere". When Royston collapsed, this is partly why things went so badly wrong for JMI.

17th August (2)

A third page on AC10 Twins is currently in progress. The roster at present is:

Late 1961 to mid 1964 - serial numbers in the range high 3400s to 4500.

Mid 1964 into 1965 - serial numbers in the range 1000-2000 (new sequence).

1965 through to 1967 - serial numbers in the range 2000 - 3200.

Please note that these pages are still building. Additions, changes, and corrections will, as far as possible, be signalled here. There is a good amount of material to come. In time there will also be a dedicated page on the Thomas Organ documentation for the AC10, which is far better in many ways than the known surviving Jennings material, and a page (or perhaps two) on the single speaker AC10 (late 1961 to 1965). Glen Lambert's pages on the earlier AC10s can be found via the AC10 Index hub.

Below, a certain fella with a cheeky little haul of Vox gear - a single speaker AC10, and so on - "TV Times", 1st-7th March, 1964.

17th August

Thomas Organ Service Bulletin no. 43, issued to dealers in February 1968. JMI was still in business (just) at the time. How did Thomas Organ know the date of manufacture of the amplifiers? Presumably from inspection tags on their chassis. Details of these are likely to have been recorded in the company's ledgers when the amps first arrived from England at Evanston and Sepulveda. Staff at the two Service Centers will also have checked the amps and set voltage selectors to 115v before dispatching consignments to dealers.

Donald John was one of those who survived the Thomas cull of the summer of 1968. Marv Kaiser, General Sales Manager and the driving force behind Vox in the USA from 1965, was not so lucky (depending on one's perspective naturally). He subsequently went on to work for Rickenbacker.

16th August (2)

Below, a detail from the "Vox Vintage Calendar 2000", which showcased the collection of Wolfgang (Wolfie) Seidel. Although some of the captions seem a little screwy to the modern eye, they were not out of accord with the thinking of the day. The amp below, which has no serial plate, is described as being an AC4 (occasionally they were also described as being AC2s). In actual fact, it's an AC6, one of around a half dozen or so currently known. There may of course be others lurking. AC6s were offered by JMI for a surprisingly long time - from March 1960 through to late 1961.

The whereabouts of the amp are not known. The "rifle" bass guitar to its right is currently in the UK.

16th August

Thanks to Nick, details of an AC30 Twin originally with a serial number in the 6000s (its plate now lacking). The Woden transformers have the date code "LT" = November 1962, and the speakers "11AH" and "15AH" = 11th and 15th of January 1963. Note that these are simply component date codes, not the date of manufacture of the chassis or amp as a whole. Components and indeed finished chassis could sit on shelves for a good while before being used. This AC30, in company with a number of others with numbers in the mid 6000s, will probably have been ready for sale in February/March 1963.

Further pics can be found here.

Chassis assembled by Burndept, number 01328.

13th August (2)

A pic of a red plasti-leather AC10 Twin cover from c. 1963, perhaps predating the introduction of new plastic handles. The opening on top seems a little small for the handle of the later amp it is pictured with. Plasti-leather Twin covers were also produced in brown and green. During the course of 1964, a new type was introduced: - thinner black vinyl with white VOX logo (early form without surround, later in a white ovoid).

13th August

A couple of items from a Jennings advert placed in the music trade press, May 1960 - the piano pick-up and amplifier vibrato control unit (also for piano).

Made by Microfisa and given a JMI transfer.

The latter, whatever its precise form, presumably plugged into the four-pin socket of the add-on Vibrato unit fitted to (certain) AC10s and AC15s built according to the Amplifier no. 2 ciruit (JMI OS/005). Thanks to Glen Lambert.

12th August

Below, the page on the AC30 in the JMI Amplifiers manual of October 1966, the majority of space given to the operation of the Top Boost circuit - the scope for "woofer" bass and "a sound that is akin to the shattering of glass". Never a truer word spoken.

Note that the idea of "stereo type effects" goes all the way back to mid 1961 in JMI promotional literature. See this page. In a number of catalogues and brochures it was also termed "split sound".

As far as the manual is concerned, there is no such thing as an AC30 "Normal" - only Treble, Bass, and Top Boost versions.

JMI Vox Amplifiers manual, printed in October 1966.

11th August

A note on Elac speakers - manufactured by "Electro Acoustic Industries Limited" in its factory in Tottenham, North London. In the late 1940s the company's main business was spares and components for television and radio sets. In the early 1950s it began to branch out into elliptical speakers and then larger conventional drivers, primarily (but not exclusively) for hi-fi applications. Below, an advert placed by Elac in "The Gramophone", March 1958.

"The Gramophone", March 1958.

In late 1960 JMI began using Elacs for its smaller amps - in particular the AC2 and AC6. These 8" drivers were by and large old stock (generally with 1958 date codes)

In the summer of 1962, JMI turned to Elac for a new 10 inch driver for its range of split-front AC10s, having largely used Goodmans up to that point. At Jennings's request, Elac sprayed the frames of the new speakers blue (as Celestion had done for the T530 for the AC30). Later, in 1963, two further types were commissioned.

Mid 1962: - 10N/81 - 10 inch, around 10-12 watts handling, 15 ohm, Jennings blue frame. Used in AC10s, wired in parallel for a total impedance of 8 ohms; and in early Line Source 40 speaker columns (late 1963), four wired in series/parallel for a total impedance of 15 ohms.

Late 1963: - 10N/82 - 10 inch, around 10-12 watts handling, 4 ohm, Jennings blue frame. Used in Vox Line Source 40 public address columns, four wired in series for a total impedance of 15/16 ohms

Late 1963: - 10N/83 - 10 inch, around 10-12 watts handling, 8 ohm, Jennings blue frame. Probably made for Watkins. It is possible that pairs were occasionally used in certain AC10s, wired in series for a total impedance of 15 ohms - but this is not certain.

Elac 10N/81 in an AC10 Twin.

During the course of 1964, JMI asked Elac to spray the frames of its speakers hammertone silver/grey - to accompany the move to new blue/grey amplifier control panels. The speakers were given a new set of model numbers:

Mid 1964: - 10N/85 - 10 inch, 15 ohm, silver/grey frame. Used in pairs in AC10s, wired in parallel for a total impedance of 8 ohms. The early 10N/85 had a magnet of the same size as the 10N/81. Later 10N/85s had smaller magnets and magnet covers ("bells") with rounded ends.

Mid 1964: - 10N/86 - 10 inch, 4 ohm, silver/grey frame. Used in Vox Line Source columns, four wired in series for a total impedance of 15/16 ohms.

One sometimes finds 10N/86s in AC10s (wired in series for a total impedance of 8 ohms), but these are likely to be replacements / later substitutions, cannibalised from Line Source columns.

So far it has not been possible to track down a 10N/84 - likely to be 8 ohm.

10th August

In the late 1990s and early 2000s - the "old days" - when pictures of amps were either very small or few and far between, there were really only three ways to determine general date: by (1) the colour of the control panel; (2) type of cabinet covering; and (3) the type of voltage selector - link or plastic dome.

Below, a couple of AC10s that go against all the axioms dreamt up back then - copper control panel AND plastic dome voltage selector. Where there are two there will probably be others.

It is still difficult to assign meaningful dates to AC10s. Large numbers of chassis were made in 1964 and the first part of 1965 - and there is often no obvious way of telling how long these sat on shelves, nor for that matter how long complete amps remained in store in boxes awaiting dispatch. The latest component date code to have emerged in any AC10 Twin so far is of early 1965. As mentioned before, Twins were still part of the JMI catalogue in April 1967.

Getting back to the initial point, it seems - again so far as one can tell - that AC10s were the only model to have both copper control panels and new-style plastic dome selectors - in other words, not the AC15, AC30, T60, AC50 or AC100. Perhaps in time the picture will change. There is nothing like being hostage to fortune where assertions about "wot they did back in the day" are concerned.

9th August

A new page has been started on later AC10 Twins - taking the picture from serial number 1000 to around 2000 (for the time being). Further material, as ever, will added over the coming days.

8th August

A small slip in the artist's rendering of the logo for the Jennings / Meazzi echo unit in the amplifier brochure of Spring 1961 - VOX ECKO. A conventional logo appears on the Echomatic photographed for the advert in "Melody Maker" in March 1961.

Detail from the brochure of Spring 1961.

Melody Maker magazine, March 1961.

7th August

Thanks to Will, pictures of AC30 serial number 13270B. This is the amp that has the factory replacement output transformer, a Woden with date code "LY" = November (not December as previously stated) 1967. Further pics can be found here.

AC30 serial number 13270.

6th August

A note on the back panel fixings of split front AC30 Twins and Super Twins. The screws adopted by JMI were brass, raised countersunk, 2BA (British Association). Cabinets were fitted by the cabinet makers with T-nuts on the inner face of the runners to receive the screws. The nuts were often recessed slightly in a drilled hole and then covered with rexine or vynide.

Below, a detail of the cabinet of serial number 4447. The disk of the T-nut is just visible beneath the rexine.

Detail of serial number 4447.

They could also simply be hammered in, standing proud of the surface of the runner, as below.

Detail from the speaker cabinet of serial number 5002.

The nuts were normally 1/2" in diameter with three spikes for fixing in the runners (which were generally 7/8" wide). It is almost impossible these days to find like-for-like replacements. Most modern T-nuts have four spikes. M5 (5mm) nuts will accept 2BA machine screws perfectly well however.

5th August

An interesting one - AC30 serial number 13230. The box and speakers (mid 1964) are still together, the former with some modifications. The chassis is late 1961 or early 1962 and from some other source. Note the phantom hole by the rectifier valve; rectangular trimpot in the preamp; and Albion transformers. The preamp has been pretty extensively renewed however.

4th August

There is now a short page on the earliest AC10 in a split front cabinet that has come to light to date - serial number 3433.

Also to signal that the page on early AC10 Twins has been updated. A page on later AC10 Twins (serial numbers beginning at 1000) to come.

3rd August

Thanks to Brendon, pictures of AC30 Twin serial number 11564, its chassis a Treble model produced for JMI by Burndept in the first third of 1964. Further pics can be found here.