Vox AC30 website updates

2026

25th April

Entries have been created/updated for six AC30 Super Twins with : 2503, 2556, 2573, 2591, 2791, and 2941.

24th April

The page on , late 1961 to early 1964, has been updated - principally to include entries for amps that had already been referenced on other pages.

In terms of balance of production, the busiest period was evidently early on, dropping off considerably during the course 1963. There are almost as many amps with serial numbers in the 5000s as there are in the range 6000-10000.

23rd April

Added - about time - to the page on , a detail from the JMI pricelist from February of that year offering for the first time amplifier sections on their own. Hard to say for sure, but it may be that relatively few were sold in this way. Contemporary photos of bands seldom show in this respect anything other than full Super Twin sets (amp and speaker cabinet).

February 1964.

22nd April

Normally seen with a later Continental with a sloping lid, below a small detail of Manfred Mann with an early one, square lid, music stand on top.

The "Vox Continental" logo was introduced by JMI some six or so months after the music stand had been phased out.

20th April

Entries created for seven AC30 Twins with - 18277T, 18640T, 18642T, 18740TB, 18780TB, 18855T, and 18894T. "TAY", one of JMI's finishers, signed in chalk the cabinet baffle of five of these amps - signing off either the finishing of the baffle itself, or perhaps the installation of the speakers. Her signature generally appears between the two T1088s.

16th April

Just a couple of - pictures for 19283 and 19410, cabinet and serial number plate only in the case of the former. The chassis and speakers currently in the cabinet were evidently introduced later, the assemblage as we have it probably dating from the 1970s/1980s.

Examples of these post-JMI and post-VSEL bits-and-pieces AC30s with Expanded Frequency copper panel chassis will be gathered together on a page of their own in due course.

15th April

On the page for Twins with , entries for 20042TB, 20136TB, 20183TB, 20612TB, 20713TB, and 20868TB have been created/updated.

14th April

There is now an entry for AC30 Twin serial number 20797 . Thanks to David for pictures and info. Further Twins with numbers in the 20000s to be added shortly.

AC30 serial number 20797.

12th April

An entry has now been added for , thanks to Darren for the pictures. There is also an entry now for AC30 serial number 7442B, thanks to Nick.

11th April

Entries created/updated for eleven AC30 Twins with : 21007, 21200, 21270, 21330, 21377, 21620, 21632, 21690, 21773, 21807, and 21994.

10th April

Entries have been created/updated for six AC30 Twins with : 22046, 22118, 22208, 22621, 22841, and 22871, all Top Boost.

9th April

Entries have been created/updated for six AC30 Twins with : 16026B, 16431T, 16574B, 16635T, 16704T and 16763T.

6th April

An entry coming shortly for AC30 Twin serial number 7442B. Thanks to Nick for the pictures.

2nd April

Published by the National Accordion Organisation, to which Tom belonged, eight issues of its quarterly "Accordion Digest" magazine. The earliest full-page Jennings adverts (known so far at any rate) were placed in these.

Below, a member's badge, and small silver and gold medals. These last were awarded during the country-wide heats leading up to the grand finale: "National Accordion Day", normally held in November. In company with Selmer and others, Jennings sponsored a cup for the winners or runners-up in various chosen categories (i.e. not the same ones every year). Tom occasionally presented the cup himself, along with the medals and awards to the other contestants in the heat.

A Jennings cup presented (not by Tom on this occasion) in Bristol in 1950:

.

31st March

A page has now been started on , used principally by JMI for smaller amplifiers from late 1958 to mid 1963, the move to Rendar coming at different points for different models: AC2, AC4, AC6, AC10, and AC/30.

JMI continued to use Re-an sockets for plug-in guitar boosters, old-style "Cliff Richard" Reverb units, and a couple of other smaller applications, into 1967.

The electronics of a JMI Treble booster from c. 1965.

28th March

A couple of useful points of reference: AC30 Twin serial number 17072 has a Woden choke with the date code "AW" = January 1965 for its manufacture. Serial number 17086 has "BW" = February 1965. Pictures to follow.

23rd March

A Goodmans Audiom 70 of the type used in certain Jennings console organs. Its original heavy-duty cardboard shipping box survives. It seems unlikely that Audiom 70s were ever used in guitar amplifiers however - they are fearsomely heavy for their size.

The Audiom 60 was generally Jennings's preference early on for AC15s and later a number of AC30s, primarily normal resonance (blue label), only one genuine example so far of bass (red label): AC15 serial number 4254.

One very early AC15 has an Audiom 50 (10 watts handling, 15 ohms). The dust cover assembly and label are of the older Goodmans type; wiring looks to be original, though currently no shot of the solder joints. Whether Jennings would have sent a 15 watt amp out into the world with a 10 watt speaker when 15 watt drivers (from various manufacturers) were readily available is the question.


Left, three squares of cardboard stuck together and cut out to fit over the speaker end cap; right, the base: two sheets of cardboard similarly treated to secure the speaker rim.

20th March (2)

The other side of the baffle of the AC100 with a logo composed of small single letters pictured below. The "V" has three lugs, the "O" two, and the "X" two. Please forgive the rough and ready outlines.

20th March

A little more on small single-letter logos. Below, a shot of the remaining letters on a Vox AC100 from the late summer of 1965 (circuit conforming to the "100W Amplifier" sheet). The "X" in this instance clearly had two lugs, one top left, one lower right. Other examples of the small single "X" have a single lug at the intersection of the arms, perhaps having been cut away from a small single-piece logo which had lugs only for the "V" and "X".

Single-letter logos are uncommon on AC100s. At present just seven are known, at least two of which will probably not emerge from their hiding place for some time yet (but they are known from photos).

AC100, serial number somewhere in the 600s (plate gone).

19th March

Two ads from the catalogue of the Electronic Components Trade Show held at Olympia in London, May 1963, the first for Rendar, , the other for Derritron, the holding company for Reslo Microphones (sold by Jennings) and Pulsonic cones, .

18th March

A provisional entry for an AC30 made by Dick Denney in post JMI days. The serial number plate - bearing the number 22572 and attached with non-standard screws - looks to have come from some other cabinet. Footpedal and control assembly aside, the amp as we have it was apparently made from disparate parts - Lemark mains transformer, Woden output transformer with February 1968 date code (i.e. manufactured five months after Dick had left JMI), and chassis with "Vox Sound Equipment Limited" chassis number.

A JMI control panel, but most else looks like "Vox Sound Equipment Limited" (1968 to late 1969).

Woden output transformer with date code "BZ".

It may be necessary to move the entry in due course as the serial number has no real bearing on the amp.

17th March (2)

Also to say that Re-an sockets were fitted in 1960 to the new two-channel "square front" AC10s - the "Amplifier No.2".

AC10 serial number 3224.

17th March

In late 1959 / early 1960, it appears that Jennings began to use Re-an, based in Dartford a few streets across from Dartford Road, for the footswitch sockets on AC/30s. Below, a detail of AC/30 serial number 4158. The same types of sockets are found also in number 4072. Re-ans do not seem to have been used for AC15s.

They were used by Triumph however for AC2s and AC4s (up to early to mid 1963).

AC/30 serial number 4158, summer or early autumn 1960, Rendars with no logo at right, Re-an at left.

Shots of a Re-an socket removed from something other than a Jennings amp.

15th March

An instance of Rendar jack sockets with patent number (the patent granted in November 1964): AC4 serial number 4870. Thanks to Chris for the picture.

As the sockets with this new legend must have taken some time to manufacture and get to market, they are probably of much the same date as the main preamp filter capacitor in the chassis (assembled for JMI by Triumph) - early 1965. The amp will not have been ready for sale until some time later though.

AC4 serial number 4798 still has "Patent Applied For" sockets.

Patent No. 974786, see the details of the patent documents a little way below on this page.

14th March (2)

The earlier types of Rendar jack socket, used by Jennings from at least mid 1958 (AC15s with blue hammertone chassis) through to early 1962. By far the most common were those with the Rendar seahorse in a roundel. Note that the threads of the examples illustrated are different, so parts were not always interchangeable. End caps came with black, brown, olive green, red, and white nuts.

14th March

A quick survey of AC30s from mid 1964 to 1968 shows that Rendar jack sockets with "Patent Applied For" legends were regularly used through to the end of production in early 1968. The latest certain example that has come to light so far is Super Twin serial number 5645 (Woden output transformer dated "BZ" = Feb. 1968 for its manufacture).

Also to say that Rendar jacks with no legend relating to the patent (the area underneath the "Rendar" roundel being entirely blank) were also used during this period, often fitted side by side with sockets that had the "Patent Applied For" line. The presence or not of legends naturally meant nothing to those assembling the chassis.

So far, no example of a socket bearing the patent number. Later today or tomorrow, a note on earlier Rendars.

13th March

Rendar plastic-bodied jack sockets with a plastic nut. So far as one can tell, JMI began using these in early 1962. Prior to that a different type of Rendar socket had been employed - moulded bakelite, the nut part of a metal barrel that screwed into the body (to be illustrated in a coming post).

Below, details from the Rendar patent for its new all-plastic socket, applied for in 1960, granted (published) in November 1964.

JMI, or perhaps more accurately its contractors, evidently bought the new-style sockets in large quantities. The example with "Patent Applied For" is one of four from an AC50 made around Spring 1965.

"Patent Applied For", one of four sockets from an AC50 from Spring 1965.

"Patent 974786".

12th March

There is now a google search widget specifically for the AC30, AC50, AC100, and Vox Supreme websites . Thanks to Paul for suggesting.

11th March

A further five entries have been added to the page for - 10113N, 10225N, 10354N, 10591N, and 10787N. There is quite a gap from 10787 to the next amp that is known for certain (10920).

9th March

Small V O X logos, single letters. In terms of dateable occurences, they first appear in late July 1964 on the AC100s issued to John and George of The Beatles - the amps said to have been ready on 17th, seen in public for the first time on 28th. Copies of the reports .

The only other AC100s fitted out in this way were retained by JMI for loan / demonstration.

Also given small single-letter logos from time to time during the course of 1964 (and in later years) were:

the AC50: the first instances probably among serial numbers in the 1180s, 1207 certain, pictures on this page.

the AC30 Super Twin amplifier section: earliest instances currently known, insofar as serial numbers go, being .

the AC4: serial number 4870 the only example encountered definitively so far.

Whether the letters always came from the supplier with lugs at back, as in the case of the "O" pictured below, is not known. The suspicion is that sometimes they were removed at Dartford Road, the plastic cemented directly to the grille cloth.

Stockholm, July 1964.

"Small "O". Other small "O"s (no longer attached to amps) appear to have had their lugs neatly removed.

8th March

Southampton c. 1960, an AC/15 (first circuit) or AC/30 with the beige grille cloth used occasionally by JMI on both models. Picture .

6th March

Quick shots of the contents of a Thomas Organ "Organs and Accessories" Service Manual from April 1967 fairly concise in scope - the Jennings-made Continental (V301J); plug-in booster units for guitar; microphones; and the Grenadier X and XII column speakers.

These manuals are often a little quirky; it is hard - these days at any rate - to find two the same.

The circuit diagrams for the Continental, all of which have long been known, are copies of JMI's, quality leaving something to be desired. The "complete schematic" - Thomas reference number 38-5495-0 - is not encompassed in this collection, possibly because it had not yet been brought into being (i.e. copied from JMI's TO/065?). The earliest copy of known date is from September 1967.

The other elements are Thomas's own though, the overview of types of tone generator board (with good photos) having been prepared initially for the "Pocket Manual" of late 1966.

Inner cover page.

Material relating to the V301J.

5th March

A page has now been set up here for (and other forms of provenance).

3rd March

Picking up from the entry below for the 26th February, a relatively early Mullard EL34 Xf1 produced by the Blackburn factory, date code "B7I" = September 1957. Production began in Blackburn in Spring '57, valves for the British market for the most part stamped "British Made", those for export "Made in Britain" or "Made in Gt. Britain".

The new bakelite base - superceding the initial Philips / Valvo metal version - made the EL34 more reliable under stress (principally heat).

The earliest dated Jennings circuit diagram to specify an EL34 seems to be the "Power Pack no. 3" (for organ) from August 1957. It is likely that the "30 Watt [Organ] Amplifier", the starting point on the face of things of the Vox AC2/30 guitar and accordion amplifier, was designed at around this time too.

Did the new source of EL34s prompt Derek Underdown to experiment and work up new designs? Intriguing to think that valves similar in date to the one below might have been fitted to AC2/30s.

April 1955.

The date code is difficult to photograph, but in the right light one can still make out "Xf1 / B7I". The earliest Blackburn made EL34 currently known is from March 1957.

2nd March

Recently to hand, a copy of the Thomas Organ Company Electronic Organ Service Manual part 2, encompassing a good number of organs from the first years of the 1960s, some all valve, others hybrid (transistor filtering and effects modules, all-valve power sections).

The circuit diagrams show that Thomas was indeed the originator of the repeat percussion circuit adopted by Jennings in late 1964, the organs in view (VL-3, VL-3A, and BL-1) being precursors to ones shown at the Russell Hotel Trade Show in August. See the entry for 8th February, below on this page.

Earlier and later Thomas repeat percussion circuits are different.

Jennings advert for Thomas, August 1964. Jennings had been appointed the main UK distributor by Thomas in the summer of 1963 and remained so until January 1967.

1st March

Thanks to James, an entry has now been made for , and the entry for has been updated and corrected.

27th February

Thanks to Chris, pictures of AC4 serial number 4889 .

26th February

Some notes coming on the use of EL34s in Jennings amplifiers (organ and guitar) in the later 1950s. Below, a copy of one of the earliest adverts for the valve in the UK - "Wireless World", April 1955. Reports of adverts from 1952 are incorrect (probably just typos as 1952 is impossible).

The valve pictured is of the earliest principal type, flattish-topped glass envelope, metal base, not ideal as it turned out for high power applications in confined spaces as the glass and metal expanded at different rates resulting in breakages. So far as is known, Jennings did not use these.

April 1955.

24th February

Thanks to László, some pictures coming of AC15 serial number 4924B, late 1962 / early 1963. In the preamp, some interesting stamps: "35574/4" and "33566/3".

23rd February

In the summer of 1972, "Vox Sound Limited" went to the NAMM show in Chicago as the "English Organ Company", a little bit of mischief as the Thomas Organ Company still held the sole rights to sell and distribute VOX equipment in the USA at this time. Below, two amps prepared either for display on the EOC stand or for an American customer (or customers) who had ordered at the show, one an AC30, the other a V100.

Trade Press, July 1972.

"English Organ Company" AC30 serial number 25905, letters in gold colour. The speakers are dated August 1972, so this amp is likely to have been ordered at the show and sent over later.

"English Organ Company" V100 serial number 1094, letters in silver.

22nd February

The - a sort of overview of surviving examples - has been tidied up and updated, further material to be added in due course.

21st February

A provisional overview of the move from thin-edged to thick-edged cabinets across the range of JMI amplifiers in later 1964:

AC4: - in the 3500s.

AC10 single speaker: - in the 4500s.

AC10 Twin: - accompanying the move to a new serial number range beginning at 1000.

AC15 single speaker: - in the 5580s.

AC15 Twin: - no change.

AC30: - no change.

AC50: - around serial number 1100.

AC100: - around serial number 220.

Below, details of two AC10 Twins:

Thin-edged cabinet.

Thick-edged cabinet.

20th February

Text entries for a further eight AC30s with serial numbers in the 22000s : 22118, 22226, 22403, 22492, 22596, 22615, 22712 and 22715. Select pictures to follow.

19th February

Further instances of second-hand Domino amplifiers in small ads:

July 1968, a Domino Bass (presumbly amplifier section only).

August 1968, a Domino Bass, unused (presumably the piggy-back set).

February 1967, surplus/obsolete stock bought in by a seller whose shop was a few doors down from the West Street Works in Erith. The Dominos were "P/B" = piggy-back.

The page on the .

18th February

Late August 1962, a couple of previews of the Jennings stand at the Russell Hotel Trade Show, the first a brief account of the new things - "Transistorisation!" - the other a list of coming models in an advert for the T60 placed in the magazine by Tom. As far as amplifiers are concerned, the review only singled out the T60 for mention. Jennings naturally referenced both the T60 and the Transonic in its ad, the two seen in pictures taken at the show.

The Radio Microphone took a good while to bring to market - an overview can be found on .

17th February

October 1968, "Exchange and Mart" magazine, an AC30 with twin 15" speakers ("Expanded Frequncy"), possibly standard production, but it could just as well have been one of the amps made up from parts purchased at the liquidation sales held at Dartford Road and the West Street Works in Erith.

16th February

June 1968, "Exchange and Mart" magazine, an AC6 for £9 (around £140 in today's money) rather than an AC4?

14th February

A detail from a copy of the "Choice of the Stars" fold-out catalogue of late 1962 sent out by Jennings to H.M.Sassoon in Singapore, probably the only Vox dealer in the Malay Peninsula at the time.

Jennings normally supplied its latest literature. The "Choice of the Stars" brochure catalogue was superceded in mid 1963, where amplifers were concerned, by the "Precision in Sound" catalogue in light blue - , entry for 15th September.

Sassoon was also the local agent for Royal Enfield motorcycles, a position he held into the early 1980s.

13th February

An entry for single speaker AC15 serial number 5646N . Its speaker is a Celestion silver (T1088) from Spring 1966 or later, solder terminals on a discrete board, though whether it is the original is difficult to tell for certain. The solder does not look new however.

Pictures to come shortly of serial numbers 4999N and 5630N, also single speaker.

10th February

Further notes on the chassis pictured below, said to have been Dick Denney's "prototype" for the AC30 Twin (1960).

Picture from Jim Elyea's book, p. 381.

1) - as mentioned elsewhere, the chassis has all the appearance of having been made by Triumph Electronics, one of JMI's principal contractors. The same sort of preamp "shelf" arrangement is also present in the first version of the Vox MC100/6, produced by the company for JMI in late 1964.

2) - insulated stand-offs (soldering points) are used throughout the preamp and power section, again typical of Triumph. One looks in vain for these in amps known to have been built at Dartford Road or by other JMI contractors (Burndept, Westrex, etc.).

3) - there is no Vibravox, only Tremolo (a single control positioned before the volume controls).

4) - the Treble and Bass controls are labelled "Presence", a term not used by JMI.

5) - the arrangement of the preamp valves - facing downwards through holes in the chassis plinth - is just bonkers.

6) - there are hum balance potentiometers for the 6.3V lines in the preamp and power section.

7) - the metalwork of the chassis is clearly passivated (electro-dipped to hinder corrosion). The chassis of single speaker AC30s were plain untreated steel through to the summer of 1960.

8) - input jacks in diamond formation are only otherwise found in the Vox AC50 of late summer / autumn 1964, assembled for JMI by Triumph.

9) - a variety of makes and types of capacitor and resistor are used. The former have date codes ranging from the 1950s through to 1964, the latest being Mullard mustards with "A4N", which can only be first quarter of '64 or, not particularly likely, first quarter of 1974. Hunts electrolytics have "WDW" = 18th week of 1961 for their manufacture. There is absolutely nothing to suggest that these, or the Mullards, were "subbed in".

10) - the valves (probably EL34s) envisaged for the octal sockets were evidently to have been cathode biased. Each socket has its own cathode resistor and capacitor (values unknown at present). The valves in the picture above are 1970s Mullards.

11) - as things stand, the screen voltage supply comes directly from the output transformer, no screen grid resistors. The OT is likely to be a replacement however for whatever was there originally. The cut-out in the chassis was evidently made for a larger unit.

Was this really a try-out for the Twin? Why no Vibravox? Treble AND Bass controls on the panel? We will doubtless return to all this in the near future.

8th February

A preliminary note on JMI's repeat percussion circuit (OS/063). There were at least two versions, one early (December 1964), and one late (December 1965 with further additions/changes). The latter was intended not only for use in the Continental, but the Guitar Organ and Electronic Accordion too.

Guitar Organ, 1966. The percussion circuit occupies around two thirds of the upper section.

JMI schema.

One of the key characteristics of the two JMI circuits as we have them (early and late) is the use of a pair of interstage transformers (T1 and T2 in the schema above). It may be no coincidence that one finds the same arrangement in an early circuit employed and probably devised by Thomas Organ. Below, a thumbnail of the sheet for the Thomas BL-3 (also known as the "Coronado"). The BL-3 was one of the models displayed by Jennings for Thomas at the Russell Hotel Trade Fair in August 1964.

Thomas Organ BL-3. One finds the same divisions on the JMI sheets - Trigger, Multivibrator, Modulator.

Later on Thomas revised the circuit, omitting the transformers, so some care (in terms of reference) is needed. Note that the sheet above, part of a large collection of material given away by Thomas when it closed its offices and service centre in West London (Alperton), is said to be "Schematic No. 2". If the collection, which is in storage at the moment, preserves a copy of "No. 1", details will be posted as a future update. The repeat percussion built into certain Thomas amplifiers and the V809 pedal, it should be said, has little to do with the circuits in view.

As has been mentioned before, the other avenue for investigation goes back much further - the transistorised effects module created by JMI for its D2 Entertainment organ.

October 1959.

The Thomas connection seems the more promising at the moment, however.

5th February

December 1956, a shortlist of regional distributors of Jennings organs covering much of mainland Britain (though not at this time Wales). Rushworth's and Forsythe's were perhaps the largest (most important) of those named. Larg and Sons were principally piano dealers, though with an unusually strong voice in the trade association through to the 1960s.

December 1956.

4th February

Thanks to Mark, pictures of Super Twin serial number 8066B (amplifier section only) have been added to the main page for and on the page for .

AC30 Super Twin serial number 8066B.

2nd February

Thanks to Bob, pictures of AC15 serial number 4755B, probably ready for sale in the third quarter of 1962, .

1st February (2)

AC30 Super Twin serial number 10253 N, what may be an early instance of an Expanded Frequency (Top Boost) chassis in its original context, i.e. still in the cabinet (and with the serial number) assigned to it by JMI. As is well known, good numbers of these chassis - some certainly having been sold "loose" in the liquidation sales of 1967 and 1968 - were at various later dates slipped into "spare" cabinets by owners and traders.

JMI it should be said also played a small part in this "redeployment", sending out a handful or two of chassis from unsold Expanded Frequency AC30s (the AC30X) as Twins in later 1964.

In terms of date codes, really the usual spread: cathode bias resistor and electrolytic caps with "UG" = July 1963; original yellow-print Mullard ECC83s with paint code "LA" = January 1964.

1st February

Music Trade Press, June 1962, the picture from this short piece posted below last week. In the final paragraph, the earliest mention that has emerged so far of the Vox Continental, which was indeed exhibited at the Trade Show in August. Evidently there was some confidence in the announcement.

June 1962. The journal corrected the statement that Williment was to head the service department (main text) in its next issue. The caption to the picture is right.

Where Cyril Windiate is concerned, the meetings at which he was to represent Jennings were of the "Electronic Organ Constructors Society", established in mid 1961, its main publication the "Electronic Organ Magazine". Copies of this magazine are extremely scarce these days. The one mentioned in yesterday's post was an unexpected find.

As the note below indicates, Jennings was scheduled to demonstrate its "transistor organs" - Continental presumably included - at a meeting of the Constructors Society in London in June 1963. A review of the event will probably have been written up for the Society (and magazine) by Alan Douglas, one of the founding members and author of some pretty fundamental books on transistor organ design. Alan was the Society's principal reviewer at this time.

Quite when Jennings joined the Society is unknown at present - perhaps not too long before Windiate was appointed though. Tom - and Jennings - only joined the "Association of Public Address Engineers" when the company's new range of PA amplifiers and microphones was ready for sale in 1964.

As for early records of the Society's transactions (from 1962 and 1963), a search is on - thanks to current members. The "Electronic Organ Magazine" did not acquire an ISBN number until 1981.

Last, simply to note that Cyril and Tom Jennings were old friends. Organist at St Aidan's in Gravesend in the mid and later 1950s, Cyril had from 1957 been a fulsome endorser of Jennings electronic church organs.

The issue in which the picture posted in yesterday's entry was published.

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