Vox AC30 expanded frequency amplifier (AC30X)

1964-1965 (and 1968)

JMI catalogue of early 1964: the first appearance of the expanded AC30.

The "Expanded Frequency" AC30 was an interesting move by JMI - the intention being to produce a sort of heavyweight version of the standard AC30 for organ and guitar. As the cabinets were open backed, the use of the AC30X for bass was evidently not a primary concern.

The chassis of the amplifier was the same size and electronically the same as that of the normal AC30 Twin. Top boost controls were advertised as being in-panel.

An overview of copper panel chassis with integrated Top Boost contols - all produced for JMI by Westrex - .

The majority of amps were produced in 1964. Note that there is no entry for the AC30 Expanded in the November 1965 pricelist.

"Melody Maker" magazine, 1st February, 1964 - an advert for the AC30 Extended Frequency with 15" speakers.

The speakers in view are 15" Celestion T900 or T1074 in blue, 15 ohms apiece, wired in parallel for a total of 8 ohms. They were given "Heavy Duty" labels by Jennings. In mid 1964, the silver versions came in - the T1109 and T1116.

Below, a great shot of the two 15" Celestion T1109s in an Expanded Frequency AC30 ("AC30EX", sometimes the "AC30X"). Note the chipboard (particle board) baffle, typical of cabinets made for JMI by Gla-Rev.

Serial number unknown. Celestion first sprayed its speakers silver for JMI in Spring '64.

Towards the middle of 1964, the cabinet for the AC30 Expanded Frequency was used as the template for the large box AC50 speaker cabinet - the two are exactly the same size. Indeed, the plan may originally have been to equip the AC50 cabinets with two 15" speakers rather than two 12" drivers and a Goodmans Midax horn. The two prototype AC50 cabinets that The Beatles had at Stockholm, 28th and 29th July, 1964, certainly had two 15" drivers - on the Vox AC100 website.

Serial numbers at first belong to the same sequence as standard AC30s, beginning around 10400 and running through to the 11000s. Thereafter the AC30X was given its own sequence, beginning at number 500 or 501 - possibly coinciding with the transition to grey control panels.

A series of standard-sized AC30s were also produced with copper panel in-panel top boost controls - serial no. 10384 being a pristine example.

By August 1964 the Expanded Frequency AC30 had been dropped from formal pricelists. The latest pricelist in which it figures was an update sheet printed for "Musicland" around Spring '64.

Detail of an update, Spring '64, to the standing "Musicland" pricelist issued in late 1963.

Detail of the JMI pricelist printed in August 1964. No sign of the Expanded Frequency AC30.

Although the AC30 Expanded Frequency only figured in JMI promotional material for a relatively short time, it is clear that reasonable numbers were produced and sold - probably through to 1965, and perhaps beyond. But at some stage more cabinets were evidently ordered than could be used. Below, an advert placed in "Melody Maker" magazine, 7th June, 1969, by Anderton's Music in Guildford - on offer, Expanded Frequency cabs, £20 each. These had probably come from the Vox Works in Erith when JMI ceased trading in late spring 1968.

"Melody Maker" magazine, 7th June, 1968.

The amp at the foot of this page, with "Vox Sound Equipment Limited" speaker labels, may have been among the units bought in at auction from JMI and finished off in late 1968. Either that, or it is a sort of assemblage of bona fide Vox parts made off-premises.

If anyone knows of further examples that should be incorporated on this page, .

Serial number 10457 - currently in Germany

Standard black "basketweave" covering. No integral top boost, so perhaps a substitute chassis. Original Celestion drivers in place.

Serial number 10459 - currently in the USA

Serial number unknown - currently in Europe

Standard black "basketweave" covering. Integral top boost. Original Celestion drivers in place.

Serial number 10471 N - currently in Ireland

Chassis assemebled by Westrex; Albion transformers. Original Celestion T900s still in place. In the preamp, WIMA red-print signal caps. The main preamp filter has the date code "UG" = July 1963. On the inspection tag, the amp is described as an "AC/36/X High Boost". The serial number is also recorded. Thanks to Alan for the pictures.

Serial number 10672 N - currently in the USA

Pebble charcoal covering. Top boost in panel; original speakers in place. The main preamp filter capacitor has the date code "UG" = August 1963. The transformers are Albions.

Serial number 11106

Further details to follow.

Serial number 11586 - currently in Europe

A superb example, complete with original cover, only one other cover known at present. Smooth grey vinyl (unusual for one of these amps). Integrated top boost controls in the control panel; original Celestion G15 (T1074) speakers with "Heavy Duty" labels still in place. The designation "X" (for "Expanded") is stamped between the panels on the serial number plate with a stamp from the set used for the model and serial number. The plate (plastic) is of a type used for a short time on AC30s in 1964. Thanks to Göran for the pictures.

Serial number 11913 - currently in Europe

Serial numbers unknown (copper panel)

Serial number unknown - currently in Europe

Probably charcoal pebble covering as on the amp above. in-panel top boost. Logo is over to the right. The cabinet has one blue and one silver Celestion - the silver will be a T1109. The label of the silver is upside down, indicating that it is likely to be a replacement from another source.

Serial number unknown - currently in the UK

Much as the amp above: charcoal pebble covering; logo over to the right; in-panel top boost. The original removable cover survives. One speaker replaced. There was a blazing row about this one on the old VoxTalks forum. A commentator posted to the effect that he bet his bottom dollar the AC30X sounded dreadful. The seller (selling on ebay.uk) found the remark and asked how the commentator could possibly know when he hadn't tried one. Things quickly got heated. Fisticuffs were promised should the two meet.

Serial number unknown - currently in the USA

Sold on ebay in November 2005. Top boost integral in the copper panel.

Serial number unknown - currently in the UK

Excellent condition. Top boost integral in the copper panel. Pebble charcoal covering. Albion transformers. In the power section, an 82 ohm cathode resistor. No "Heavy Duty" labels on the speakers.

New serial number sequence beginning at 500.

Copper then grey control panels. It is likely that a certain number of amps - serial number 11586 (above) for instance - were still assigned numbers in the standard Twin sequence after the new AC30X had been kicked off.

Serial number 505 - currently in the UK

Cabinet in smooth dark grey vinyl. The amp is in full working order; one speaker Jennings blue, the other Jennings silver. Thanks to Stuart for the pictures.

Serial number 549 - currently in the USA

Existence reported by Jim Elyea, p. 400.

Serial number 565 - currently in the USA

Grey control panel. Black basketweave covering. Still brown grille cloth. The speakers have been replaced with ceramic 1970s Goodmans.

Serial number 589 - currently in Europe

Stamped "0589". Burndept chassis number 9699. Grey panel with integral top boost. Dome voltage selector. Still brown grille cloth. The cabinet covering is standard basket-weave vinyl. Speakers are Celestion T1109, sprayed silver.

Serial number 593 - currently in Europe

Chassis possibly assembled by Westrex. Slot voltage selctor. The mains transformer is a Woden - date code "EW" = May 1965. Choke and output transformer look to be Albions. The original 15" Celestion T1109s are still in place.

Serial number 596 - currently in the USA

Existence reported by Jim Elyea, p. 529.

Serial number 602 - currently in Europe

AC30 X 15, serial number 602.

Thanks to Daniele, pictures coming shortly of AC30 Expanded Frequency (2 x 15" speakers) serial number 602, grey panel, late 1964 (provisionally).

Serial number 604

Existence reported by Jim Elyea, p. 529.


Serial number unknown - currently in the UK

Grey panel with integral top boost; link voltage selector. Celestion T1109 speakers.

Serial number unknown - currently in the UK

A strange one, perhaps put together by "Vox Sound Equipment Limited" in 1968 - note the speakers. The grey panel chassis has no in-panel top boost. But the box has brown cloth. The cabinet has a standard black basketweave covering.