The AC30 Super Twin as represented in the JMI dealer's catalogue of early to mid 1964. It should be said that very few Super Twins at this date will have looked like the one depicted. Most (if not all) speaker cabinets had split fronts.

In 1964, JMI embarked on a massive stepping up of production. Demand was increasing exponentially. Something in the order of 7,000 AC30s were produced during the year, a proportion of which were naturally Super Twins, and Super Twin Reverbs.

The chassis that went into Super Twin amplifier cabinets seem as a general (though not infallible) rule to have been those assembled for JMI by Westrex.

Earlier Super Twins are on this page; and early Super Twin Reverbs (with rectangular rather than trapezoidal amplifier cabinets) can be found here.

A little way into 1964, the Super Twin was given its own numerical sequence - beginning with serial number 2501. At much the same time the AC30 Expanded Frequency model was given its own sequence too. Now and again one finds, however, Super Twins with numbers that should, strictly speaking, belong to Twins - no. 12635 for example (included below). Errors of this nature doubtless crept in from time to time, though one must always allow for the swapping of chassis, boxes and plates in later decades of course. But generally one can tell - in these latter cases the disparity between serial number and the cosmetics and electronics of the amp in question are normally readily apparent.

Below, thanks to Robert Valentine, who worked for JMI from 1959 to 1964, some details from a photo taken in 115 Dartford Road in late July 1964. The occasion: the visit of The Barron Knights, who went away with a pair of LS40 PA speaker columns; new AC30s; and two AC50 Foundation Bass sets. The AC50 amplifier sections were diamond-input small-box. On the far bench, AC30 Super Twin amplifier sections being made ready for use. On the near bench, a variety of cabinets being finished off. To the right of the AC30 Twin, a Goodmans Midax horn for a large-box AC50 speaker cabinet.

An AC30 Super Twin chassis about to go into its wooden case.

In the case of the Twin, evidently the last thing to be fitted (where cosmetics are concerned) was the "VOX" logo. Serial number and ID plates were attached later.

Just to note that model and serial number were still hand stamped in 1964. "N" stands for normal voicing, "B" for bass, "TB" for "Top Boost", and "T" for Treble. On the treble circuit, see this page.

"Melody Maker" magazine, 21st March, 1964. Prices given for the Super Twin Normal and Super Twin Bass.

Cabinets are for the most part black (i.e. aside from custom colours), the covering being basketweave vinyl. One still finds pebble (dimpled) and smooth black vinyl though. Grille cloth is brown at first. Black comes in periodically later, beginning with serial numbers in the high 2700s. But the change from brown to black cloth took some time to work through, as did the change from copper to grey control panels.

Full swivel trolleys were introduced in late 1964 / early 1965, though generally (operative word) only for AC30 Super Twin Reverbs. The earliest have a rectangular "basket" on top, wider than the parallel bars, to support the amplifier. Survivals are extremely scarce. Later one finds "standard" trolleys with plain parallel bars. The "basket" was phased out due to cost.

In late 1964, another solution was ventured - the amplifier (note the sloping sides) supported by small chrome brackets. But so far as one can tell, this never went into production:

"Precision in Sound" newspaper format catalogue, late 1964.

Finally to note that AC30 Super Twins designated as "Treble" models on the serial number plate first appear in the high 2500s. Treble-voiced Twins start appearing in quantity in the 11000s, though there is at least one in the 10000s.

If anyone knows of further early Super Twins that should be incorporated on this page, do let me know.

SERIAL NUMBERS IN THE STANDARD TWIN SEQUENCE

1964

Serial number 10081 B - currently in the UK

A Super Twin amplifier section. Albion transformers.

Serial number in the 10000s - currently in Japan

Note the integral top boost controls in the copper panel.

Serial number 10472 N - currently in the UK

Still part of the main AC30 numerical sequence, a Super Twin.

NEW

Serial number 10753 N - currently in the UK

A Super Twin amplifier section. Chassis assembled by Westrex, copper panel, top boost controls integrated. One of the gold-coloured TCC 25uf caps has the date code "UC" = March 1963. The underchassis is signed in pencil "DP" with an "X" in a circle (to denote "expanded frequency").

Serial number 11076 N - currently in the UK

Grille cloth replaced - currently Rose Morris (from the 1970s). Albion transformers. The serial number plate has at its head "AMPLIFIER" rather than "VOX AMPLIFIER". The number itself overlies a first effort at stamping.

Serial number 11421 N - currently in the UK

Note the discoloured serial number plate, typical at this point of production.

Serial number 11575 N - currently in Europe

Basketweave vinyl; brass vents on the box. No red dye on the solder joints, so probably assembled by Burndept. Albion transformers and Parmeko choke. One of the blue Hunts cathode bypass capacitors has the date code "WTT" = 14th week of 1964. Mullard mustard capacitors have the date "B/64" and "B4N" = second quarter of 1964.

Serial number 12333 B - currently in Italy

A Super Twin, amplifier section and speaker cabinet, the BASS flag still present on the front grille.

Serial number 12501 (recte 2501?) - currently in Europe

Not a mistake for number 2501, as previously suggested, as 2501 has recently come to light (Oct. 2021)

Serial number 12xxx N - currently in Japan

Another Super Twin, normal voicing. Transformers are Albions. The chassis is likely to have been assembled by Westrex.

Serial number 12635 N - currently in Europe

A further instance of a Super Twin with a number that would normally be reserved for a Twin. The voicing is given as Normal ("N"). The cab was said to contain "silver bulldog" speakers - ie. Celestion T1088s.

Serial number 12897 N - currently in the USA

Smooth dark grey vinyl. In panel top boost.

NEW

Serial number 12907 N - currently in the UK

Copper panel; Albion transformers, complete with its original speaker cabinet. One of the Celestion blues has the date code "25BJ" = 25th February 1964.

Serial number 13240 - currently in the UK

As below, a Super Twin with a serial number in the Twin sequence.

Serial number 13273 T - currently in Europe

A Super Twin, its number in the main AC30 Twin sequence.

THE NEW SUPER TWIN SERIAL NUMBER SEQUENCE

Beginning at number 2500

Serial number 2501 N - currently in the UK

Chassis assembled by Westrex; Albion transformers. Cabinet covered in thick dark grey vinyl; black vents still in place. In the preamp, the gold-colour TCC cathode bypass caps have the date code "TM" = December 1962; WIMA signal and coupling capacitors throughout. Presented for sale again in late 2021 on top of a Super Twin speaker cabinet obtained from some other source.

Serial number 2509 B - currently in Europe

Probably Albion transformers.

Serial number 2525 N - currently in the UK

Below, further pictures, principally of the preamp:

Chassis assembled by Westrex and stamped in blue at left "Westrex Treble". It is indeed a Treble model. The serial number plate gives the voicing however as Normal ("N"). In the preamp, WIMA signal and coupling capacitors. The speaker cabinet has what look to be the original Celestion blues (T530). Sold on Reverb in August 2020.

Serial number 2541 TB - currently in the UK

Albion transformers. "TB" (Top Boost) indicated on the serial number plate, though the controls themselves have been removed.

Updated

Serial number 2562 - currently in the UK

A grey panel chassis with in panel Top Boost - probably not original to the box. Note the dome voltage selector. The serial number is plain "2562", ie. Normal voicing, not Top Boost. See serial number 2583 below.

Serial number 2569 T - currently in Germany

Charcoal grey vinyl; grille cloth renewed. Transformers are Albions; preamp in good original order, red-print WIMA signal and coupling capacitors throughout. An early Super Twin Treble model. Original wiring and speakers still present in the speaker cabinet, the baffle marked "8" in chalk and the inside of the back panel "VIII", so that the two could be matched up again if separated. The speakers have Pulsonic cone code "4H1777", which aligns with late winter / early Spring 1964 for their manufacture. See this page.

Serial number 2583 TB - currently in the UK

Top boost in panel.

Serial number 2589 N - currently in the UK

The only change a replacement handle; excellent condition externally. Thanks to Robert for the pictures.

Serial number 2592 TB - currently in the UK

Marked as "Top Boost" on the serial number plate, the controls still on the back panel.

Serial number 2599 N - currently in Europe

"Westrex Treble" is stamped on the aluminium of the preamp. "Normal" voicing - "N" - is marked on the plate however. Details of the preamp show that this is indeed a "Treble" model. The Celestion blues have date codes 24FH and 27FH = 24th and 27th of June 1963.

Serial number 2605 T - currently in the USA

The serial number plate of Super Twin 2605 now affixed to a 1963/1964 AC30 Twin cabinet containing an earlier chassis.

Serial number 2617 T - currently in the UK

Sold by Gardiner Houlgate (auctioneers) in 2012.

Serial number 2665 T - currently in Germany (?)

Exterior shots only. Thick speckled grey vinyl. Black metal vents. Corner protectors renewed - now with double pins. There are five screws across the top of the back panel, three for the chassis, two for the cabinet. On the back panel, jack sockets (with escutcheons) for use with 8 or 15 ohm cabinets.

Serial number 2673 N - currently in the UK

Chassis assembled for JMI by Westrex and stamped on the preamp at left "T B" for Top Boost. Note that the serial number plate gives the voicing as "Normal". Grey control panel, top boost controls integrated. Albion transformers, the output transformer replaced. In the preamp, WIMA signal and coupling capacitors.

Serial number 2681 B - currently in Europe

Smooth dark grey vinyl; Bass voicing. Originally sold by Servaas Muziekhandel in The Hague.

Serial number 2687 T - currently in the USA

Marked on its serial number plate as being a "Treble" model.

Serial number 2690 - currently in the Netherlands

Chassis assembled by Westrex. Top boost controls on the control panel. Signed off in pencil underchassis "DP" and the familiar "X" in a circle for "Expanded". Transformers and choke made by Albion. In the preamp, WIMA signal and coupling capacitors. The main preamp filter cap has the date code "UG" = July 1963 and the larger green TCC cap for the Top Boost circuit "UF" = June 1963.. In the power section, the cathode bypass resistor in the power section is the original 50R; the TCC bypass cap has the date code "UF" = June 1963.

Serial number 2714 T - currently in the UK

A good few changes. Chassis assembled by Burndept, Woden output transformer ahd choke with date code "AU" = January 1963; mains transformer "BU" = February '63. The question is whether this chassis - which should be a Treble - is original to the box.

Serial number 2729 T - currently in Sweden

Accompanied by a speaker cabinet (unlikely to be the original) with alnico blues dated 21st May 1963.

Serial number 2731 T - currently in the USA

Copper panel just discernible.

Serial number 2733 T - currently in Europe

Copper panel; Treble voicing (going by the designation on the serial number plate).

Serial number 2739 T - currently in the UK

Chassis assembled by Burndept, number 05214. Grey panel with integral top boost; brown grille cloth; link voltage selector. The original burgundy covers survive. Hunts caps visible in the preamp have the date codes "WHT"and "WTT" = 12th and 14th weeks of 1964. Note the presence in the preamp of a number of Mullard "mustard" caps (which look to be original), date codes "A4N" and "B4N" = first and second quarters of 1964 for their manufacture.

Serial number 2751 TB

Only the serial number plate, removed from amplifier.

Serial number 2791 T - currently in the UK

Chassis assembled by Westrex and stamped "Westrex Treble" in purple under the input jacks. The number "130" was added in pencil. Albion transformers. In the preamp mainly WIMA red print signal capacitors. The date code of one of the gold-coloured TCC 25uf caps is some point in 1963 - only the "U" is visible. Three jack sockets have been added to the back panel.

Serial number 2798 - currently in the UK

Black grille cloth; lower right, the runner "Top Boost 30". Chassis probably made by Westrex. Grey control panel, integrated Top Boost controls; link voltage selector. The transformers are Albions. No indication of voicing was stamped on the serial number plate.

Serial number 2810 T - currently in the UK

Sold on ebay uk in November 2023. Various holes let into the back panel for sockets, the footswitch evidently well used (a repair to the top).

Serial number 2833 B - currently in the UK

Basketweave vinyl. Brown grille cloth; copper control panel. Woden transformers: choke and output transformer have the date code "KU" = October 1963; the mains transformer "LU" = November 1963. The speakers have Pulsonic cone code "19H1777".

Serial number 2838 B - currently in the USA

Brown grille cloth and copper control panel. The speakers are Celestion silver T1088s - so after May 1964. One has been mounted with its label vertical rather than horizontal.

Serial number 2879 - currently in Europe

The hand-stamped serial number is followed by "SR" which should mean "Super Reverb", but there is no sign that there was ever a reverb tank, nor does the back panel have the requisite controls. The chassis assembled by Westrex and stamped "Westrex Treble" in purple in the preamp under the jack sockets. Albion transformers and choke; gold-coloured WIMA Tropyfol signal capacitors throughout the preamp; gold-coloured TCC cathode bypass caps. The main preamp filter capacitor has the date code "UG" = July 1963.

Serial number 2899 T - currently in the UK

Brown grille cloth and copper control panel. Albion transformers. Slightly difficult to see, but the preamp is stamped "Westrex Treble". The second set of pictures from a second sale of the amp.

Serial number 2901 TB - currently in the UK

Chassis assembled by Burndept; the chassis number originally stamped 04475 - changed to 04476. Grey panel with integrated Top Boost. Note that the voicing is also designated "TB" on the serial number plate. In the preamp, a mixture of Mullard mustard and WIMA coupling capacitors. The date codes on the Mullards are difficult to read unfortunately. One certainly has "../64" and another "D..N", either D3N or D4N (last quarter of 1963 or 1964). The mains transformer (with the Lemark label) is a replacement from a later amp.

Serial number 2911 N - currently in the USA

Designated "Normal" on the serial number plate, but the chassis is a Treble (as serial numbers 2929 and 2939 below), assembled by Burndept. In the preamp, Mullard mustard capacitors with date code "B/64" = second quarter of 1964. Transformers probably Albions (less likely Parmeko, certainly not Woden).

Serial number 2929 N - currently in the USA

Chassis assembled by Burndept, number 3654. The voicing of the chassis is marked as being "Treble". The serial number plate of gives the voicing as "N" = Normal, however. Transformers are Wodens with date codes "MU" and "AV" = December 1963 and January 1964.

Serial number 2939 N - currently in the UK

Chassis - Treble voicing - assembled by Burndept. Parmeko transformers. The Mullard mustard capacitors in the preamp have the date code "B4N" = second quarter of 1964. The flash of red paint on the preamp at right should mean that this is a Treble chassis. In the speaker cabinet, blue Celestion T530s, one with Pulsonic cone code "9H1777", used in speakers made in May 1964 - see this page. The amp was probably ready for sale early in the last third of 1964. Thanks to Neil for the pictures.

Serial number 2960 T - currently in the UK

Chassis assembled by Westrex. Albion transformers and choke. Signal capacitors in the preamp are gold-coloured WIMA Tropyfol. The main TCC filter capacitor in the preamp has the date code "UG" = July 1963. Originally sold by Johnson Electronics (Lesjay Limited) in Sheffield, which seems to have done good business with AC30s.

SERIAL NUMBERS UNKNOWN

Currently in Canada

Smooth dark grey vinyl. Albion transformers; chassis assembled by Westrex and marked "Westrex Treble". Thanks to Glen for the pictures.

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