Vox AC30 website updates

October 2022

31st October

A note on Celestion blues in :

- up to around serial number 4200, third circuit AC15s were issued in TV Front cabinets, thereafter in new split-front cabs (from serial 4208 certainly).

- the earliest AC15 currently known with an original Celestion blue is serial number 4433. The most recent seller of the amp reported the speaker's date code as being 18th July 1961, in other words "18GF".

- serial number 4408 has an oyster-coloured alnico G12, probably either a CT3757 or a pre-blue T530.

- AC15s prior to serial number 4408 generally have G12s too. The Audiom 60 in serial number 4320 may be a later substitution.

A couple of points follow: (1) there is no correlation between the introduction of the new split-front cabinet and the introduction of blues (obvious in any case); and (2) it evidently took some time for JMI to move to fitting the new speakers in AC15s. Blues were registered as a new model in the Celestion log books between November 1960 and January 1961.

There may be a number of reasons for the apparently slow adoption of blues in AC15s. (1) JMI could have been using up old stock, reserving the new speakers for AC30s; (2) alternatively, AC15s may have been made up in relatively large batches resulting in gaps between production runs; (3) or it could simply be that blues came in much later than we think. The earliest example that has come to light so far is from May 1961.

30th October

Thanks to Eoin, pictures of AC15 serial number 4293, first quarter of 1961.

AC15 serial number 4293.

29th October

Thanks to Michael, pictures of AC30 Twin serial number 15877TB, probably made in the third quarter of 1964. Purchased second-hand in 1975 for £50.

AC30 serial number 15877TB.

28th October (2)

A short paragraph has now been added to the page on . Thanks to Danny for signalling the lack of mention of the 72318 & J/82.

Towards the end of 1963, however, the mains transformer - 66309 & J/82 - was superceded by a new version designated 72318 & J/82. The suspicion is that JMI asked for the secondaries to be adjusted - specifically the main HT voltage. Batches of the new unit were produced with date codes "JU" = September 1963 through to "AV" = January 1964, that last batch being fairly sizeable. It is probably no coincidence that 72318 followed (in relatively short order) the modification of the cathode bias circuit (June 1963) - the main bias resistor changing from 80R to 50R.

28th October

Thanks to Jim, pictures of AC30 Super Twin serial number 5327N, probably from May/June 1962. The tone pot has the date code "DJ" = April 1962. The Celestion blues have cone code RIC 1 JC (possibly JL). Further pics .

AC30 Super Twin serial number 5327.

26th October

Some notes on AC30 full length stands - a sort of parallel to the page on swivel stands posted yesterday. The name of the company that made the early tubular stands is not known at present. Castors were bought in by JMI from Kenrick Shepherd.

A stand from 1963.

Kenrick castor: diameter of wheel 2"; shaft 1 3/8" tall and 5/16" diameter.

The frame of the stand was made from tube with an external diameter of 5/8" and an internal diameter of 1/2" - in other words, with walls 1/16" thick.

In order to make the shaft of the castor (diameter 5/16") fit inside the tubing, an insert was required. These go by at least three different names - castor "inserts", "sockets" and "sleeves".

JMI used small hard plastic inserts 3/4" tall; 17/32" outer diameter (to give some friction when compressed inside the tubing); and with a rim at foot 3/4" in diameter (so that the insert could not slide fully into the tube).

25th October

A page on swivel side stands for AC30 (and AC15) Twins has now been , further material to be incorporated shortly.

The side stand of AC30 serial number 22789. The stand (invoiced in June 1968) cost £25.00

24th October

Screengrabs from The Shadows' set ("FBI" and "Frightened City") on "Crackerjack", a popular children's programme, BBC 1, 27th April, 1961, 5.10pm-6.00pm. The earliest firmly dated sighting of Celestion T530s?

Or are these speakers too light to be blues? - in which case Goodmans Audiom 60s? Hard to tell definitively though given the low resolution and the nature of reflected light. Blues seem most likely. The last picture seems to show the curvature of the bell

The three new split-front AC30 Twins in a sort of U formation. The amps were first seen in public in March 1961 at the NME Poll Winners show.

23rd October

A Celestion blue (T530) with date code "11GF" = 11th July 1961. Only part of the code - "04", perhaps the 4th July - remains on the speaker to its right. The cone codes were not photographed.

Below, a pair of T530s from December 1961 with reversed letters in their codes - "22FM" (on the left), "19FM" (right) . "M" is not possible as a year for blues. The codes should be "19MF" and "22MF", the 19th and 22nd of December, 1961. The same error occurs on a pair of blues stamped "22FM" in the speaker cabinet of AC30 Super Twin serial number 5002 - .

Cone codes: RIC 1 DJ, as on the speakers of serial number 5002.

22nd October

A shot of a Celestion T1088 with Thomas part number (as in the AC30 parts list below) in a Thomas Vox Super Beatle speaker cabinet. In late 1965 Thomas struck its own deal with Celestion for various models of speaker recommended by Dick Denney - Denney visited Sepulveda in late October '65. A report of his visit {and recommendations made) was sent to Tom Jennings a few days later - printed in the "The Vox Story", Petersen and Denney, 1993, Appendix 3.

The earliest T1088s exported to Thomas had solder terminals on their frames - examples survive in V-14 Super Beatles. The majority, however, being later, had discrete boards, as below, between the spokes. JMI supplied the labels.

21st October

Picking up from yesterday, smaller electronic and cosmetic replacement parts were generally supplied (to dealers) by Thomas in sealed plastic bags. This one contains two unidentifiable plastic fittings.

The site of the Service Center at 16641 Roscoe Place is now occupied by Hope of the Valley Mission (a new building).

20th October (2)

Below, pics of the cover and pages relating to the AC30 of the Thomas Organ consolidated parts list of April 1969, issued to dealers throughout the USA - "dealer" and "retail" prices given.

Although Thomas's last major order for English-made JMI amplifiers came in early 1966, spare parts and "accessories" - covers, trolleys, stands, and so on - continued to be a need. The JMI side stand swivel assembly is number 09-5328-0, $20.40 to dealers, $34.00 retail.

Note that the replacement rear cover panel (upper back board) - number 09-5322-0 - came complete with serial number plate - with number stamped?.

20th October

A pair of Thomas Organ side stands, made for the solid state Viscount amplifier, early 1966 to around 1969, imitating JMI, but with notable differences. The legs for instance are more sharply angled and the swivel mount is open.

Thomas Organ side stand for a solid-state Viscount amplifier.

The swivel hardware was different from JMI's too, the cabinet mount a simple plate (3" diameter) with welded thread, and the "VOX" logo incised rather than stamped on the hand-wheel. The plain metal disk went between the hand-wheel and the hoop at the apex of the stand (picture 3 above).

Thomas Organ side stand hardware.

19th October

A detail from a rough print of a picture taken at the - a promotional AC30 in perspex with old-style hand-wheel, the VOX logo in cursive.

Pictured darkened to show the logo on the hand-wheel more clearly.

The first style of JMI hand-wheel, 1963 to autumn 1964.

The side-stand arrangement of the first of the two perspex AC30s illustrated by Jim Elyea is unfortunately factitious (not of his making). The hand-wheels are later 1960s US-made Thomas Organ parts. The same may be true of the second.

Thomas Organ-made hand-wheel, "VOX" in plain thinly-incised letters. See yesterday's entry for another.

It is also worth noting that the amp, or at least chassis of the amp above is a Treble model - indicated by the flash of red paint on the preamp upright - and so is from 1964 or later. It has nothing to do with the 1963 Fairs. Nor is it the amp pictured at the London show of autumn 1964 - which leaves, if the chassis (with its copper panel) does indeed belong to the cabinet, the Frankfurt Musikmesse of February 1964 and the NAMM show of June/July as the only events possibly in view for its production. But too many questions remain.

Flash of red paint at right on the chassis indicating a Treble model. For the Burndept paint codes for voicings, .

Lastly to note that the perspex AC30 currently being offered for sale ion Germany has a fully chromed chassis, including the preamp side. The preamps of purportedly "original" perspex AC30s appear to be chromed too - apart from the one above. [updated 19th Oct.]

18th October

Further notes on JMI trolley and side stand hardware.

Swivel side stands were developed initially for Line Source 40 public address speakers. In late 1963 / early 1964, JMI adapted the idea for AC30s.

Side stands, front and back.

The cup of the side stand locates over a metal mount fixed to the side of the amplifier cabinet:

Trolley / side-stand cabinet mount. Dimensions: diameter 3"; body 1" tall, 1 7/8" diameter; threaded centre 1 1/2" tall; thread diameter 3/8" (British Standard Whitworth).

When fitted at factory, mounts were generally attached to the sides of the cabinets with 1 1/4" 2BA machine screws (through pre-drilled holes) and secured inside the cabinet with a plain washer, grip washer, and nut.

Friction washers for the assembly were of two types: rough fibre (the most common type) or translucent nylon. These slotted over the central drum of the mount, lying flush against its outer rim. In 1967 metal washers were sometimes used instead of fibre or nylon.

Dimensions of the washer on the left: diameter 2 15/16"; width 1/2" to 9/16". The material: a species of resin backed emery cloth.

A handwheel locked the cup of the side stand tight against the friction washer. The pair below came from a set of LS40 speakers.

First style of hand-wheel design.

Various bands had stands with hand-wheels of this type: The Dave Clark Five, The Shadows, and The Beatles - Paul's AC100 trolley, and from May, John and George's AC50 trolleys.

In the JMI catalogue of early 1964 (printer's runner February '64) the swivel side stands were £10 and 10 shillings, a sizeable amount - equivalent to around £150 today.

Detail from a picture of the Barron Knights with new equiqment on the forecourt of 115 Dartford Road, late July 1964. Note the Kenrick / Shepherd castors. These were soon superceded by Flexello wheel units. Thanks to Robert.

By early August 1964, JMI had moved to a new style of hand-wheel with stamped rather than incised logo. On the left below, the new-style JMI hand-wheel; on the right, a battle-scarred example of a Thomas Organ wheel from 1966/1967. Thomas Organ incised its VOX logos.

JMI left; Thomas Organ right.

The earliest firmly dated instance of this new logo currently known on AC30 side stands is in photos taken for JMI in September:

Photos taken for JMI in September. The new logo is apparent in the original print of the left-hand picture.

Below, the reverse of the JMI and Thomas Organ hand-wheels:

JMI left; Thomas Organ right.

17th October

Recently come to light, one of the last AC30s produced by the Birch-Stolec factory in Hastings, late 1972 / early 1973, AC30 TBR serial number 1300 - the highest serial number known at present - . The amp has its original Celestion alnico T2056 speakers. Thanks to Andrew for the picture.

15th October

Thanks to Nigel, pictures of AC30 Twin serial number 5407 from mid 1962, the cabinet recovered with black basketweave vinyl in the late 1960s / early 1970s, covering up the original holes for the handles. At this time, a number of capacitors in the preamp were renewed.

In terms of date codes of original components, the main Hunts preamp filter cap has "WSH" = 15th week of 1962. The copper control panel is of the earliest type (with "JMI" in tall thin letters). A number of black WIMA Tropydur caps remain in the preamp. Further pictures .

AC30 Twin serial number 5407, mid 1962.

11th October

Below, pictures of a semi-closed (or semi-open depending on one's view) Vox AC30 speaker cabinet from 1965, the solder terminals of its Celestion T1088s still on the frames rather than separate tag-boards (an innovation of early 1966).

Such cabs were probably introduced at much the same time as the slope-sided - "trapezoidal" - AC30 SRT amplifier section. They may also have been sold on their own as "extension" units. No example has come to light so far from 1964.

Circular Amphenol XLR sockets are a thing of 1965 too, probably mid. They are first seen on AC100s with serial numbers in the 500s, and on AC50 speaker cabinets accompanying amplifiers with numbers in the high 2000s. Amphenol's factory in the UK was on the outskirts of Whitstable, just down the coast from Dartford and Erith.

The switch to this new type of connector evidently followed the move to West Street Works. From 1962 through to mid 1965, JMI generally used Cannon or Geloso XLR sockets and connectors.

The back boards take the same form as those of the AC30 Twin.

10th October

Four new entries - principally text for the time being - added to the page on AC30s with .

5th October

Although no precise date is known for end of the contract with Westrex at present, early Spring 1965 seems most likely. This is borne out by AC100s. Up to and including AC100 serial number 306, all chassis were assembled by Westrex. From number 320 if not slightly earlier, production in its entirety (speaker cabinets as well as amplifiers) was moved to Erith. AC100 serial numbers 320-430 all have Woden transformers with "BW" date codes = February 1965.

Substantial orders only really began to come in - principally from the USA - at around this point, ie. early 1965. Prior to that Westrex alone was able to meet JMI's needs.

For AC30 Super Twins, the picture is similar: mostly Westrex chassis up to around serial number 3900, Burndept/Vox Works thereafter - a fairly "clean break".

For AC30 Twins though, the picture is slightly less clear: there are small batches of Westrex chassis throughout the 18000s and through to the mid 19000s, but it is hard to make out any particular patterns of use. There seems to be no "clean break" as there is for Super Twins. And one has to factor in the evident over-production and over-ordering of parts in 1964. Twins did not do well in the USA. JMI had plenty of stock to sell in Europe.

3rd October (2)

Just to add that the main preamp filter capacitor in serial number 22976 (below) has the date code "TDS" = 48th week of 1965, so relatively old when the amp came to be assembled in 1968.

Detail of AC30 serial number 22976TB.

3rd October

Thanks to Nick, pictures of AC30 serial number 22976TB, close to end of JMI days, the Woden output transformer with date code "BZ" = February 1968 - .

Note that the serial number plate has at its head "AMPLIFIER" rather than "VOX AMPLIFIER". In mid December 1967 JMI went into receivership and was evidently no longer able to use the old-style plates. The new "AMPLIFIER" plate is also found on late JMI AC50s and solid state amps.

AC30 serial number 22976TB.

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