The Vox AC2 - late 1960 to 1962

4 watts, one channel, single- or two-input versions

Jennings Dartford Road Works before May 1961

Above, a shot of the Dartford Road Works taken in late 1960 / early 1961, published May 1961 - rows of amplifiers waiting to be dispatched. Far right, AC2s? Left-hand side, a second row of blue and grey AC15s (with diagonal division between the colours).

The AC2 was first produced in late 1960 - not 1959 or early to mid 1960 as is sometimes said. Serial number 2027, pictured below, came with its original valves, date codes April 1959 to November 1960.

It is also worth recording that the AC2 does not appear in any *dated* source until November 1960. Nothing has emerged so far in the promotional literature and adverts from May to October. The AC6 on the other hand was promoted from December 1959 to December 1960.

In November (in Melody Maker), the AC2 is listed in two versions - two input (17 guineas), and single input (12 guineas) - both are said to be 4 watt amplifiers. Vibrato (actually tremolo) is stated as being present.

"Melody Maker", 19th November, 1960. The same advert was placed on 12th Nov. under the heading "Vox Amplifiers and Guitars".

A detail of the relevant lines.

By December 17th 1960, the single input version disappeared, not to be listed again. Very few are likely to have been produced (and sold).

"Melody Maker", 17th December, 1960.

A detail from the earliest version of a brochure printed in early 1961 for "Musicland" in Bexleyheath, managed by Paul Jennings, Tom's son. The AC2 is the only amp illustrated.

Note that the power output of the AC2 in the catalogue above is given as a huge "6 Watts". In 1962, some months after the AC2 had been redesignated the AC4, power output was noted as being "2 Watts", the circuit exactly the same.

Below, some provisional notes on the various changes that took place during production. These will be expanded (and illustrated) soon.

SERIAL NUMBERS

AC2

1) Late 1960-1961. Fawn or "tan" covering, perforated hardboard back, "AC2" designated on plate, single input or two input versions. Small box with thin edges. Control panel an "island". Two-input AC2s have a black control plate with legends: INPUTS, VOLUME, SPEED, ON/OFF TONE. The single-input version has no plate at all. The legends, printed on black traffolyte, are applied to fawn vinyl stuck a wooden block. Both models have circular, ribbed, black control knobs. Serial numbers begin at 2000.

sn. 2020 - AC2, single input, tan cloth, perforated hardboard back.

sn. 2027 - AC2, single input, fawn cloth, perforated hardboard back. The amp is pictured above (entry for 14th July). Probably original valves, latest date code = Nov. 1960. CCL main filter cap (32uf+32uf) date code "L8" = December 1958. Two pots have codes: "OT-116NI", and "411/9 4 CTB".

sn. 2067 - AC2, two input, fawn cloth, perf. back.

sn. 2104 - AC2, two input, black control panel, fawn cloth, perf. back. Hunts signal capacitors have date codes "WSY" = 15th week 1960. CCL main filter cap (32uf+32uf) date code, letter "L" probably followed by "8", as in serial number 2027, above = December 1958.

sn. 2137 - AC2, two input, black control panel, fawn cloth, perf. back.

sn. 2141 - AC2, two input, black control panel, fawn cloth, perf. back.

number unknown - no plate, fawn cloth, black control panel, round black knobs, no view of back.

2) Late 1961. Mainly as above, but with a two-piece birch ply back. The earliest AC/2 circuit diagram known is dated 9th December 1961 (see a little way below for a copy).

sn. unknown - AC2, two piece back, old-style black control panel. Diamonds of grille cloth upright. Now has a repro plate (of the wrong sort) with the number 2102.

sn. 2189 - AC2, two piece back, new-style pink control panel.

AC4

3) Late 1961. Same format of box as above, but with slightly thicker edges. Still the "island" control panel, the control panel pink in colour. The amplifier now called the AC4. Grille cloth with diamonds orientated sideways. Larger VOX logo. The electronics were laid out in a more consistent manner from this point - a horizontal ground buss rail introduced, tidier wiring, etc.

Chassis assembled now for JMI by Triumph Electronics. According to the late Rodney Angell, who worked for JMI in the 1960s as amp tester and service engineer, Triumph had been brought in initially with a view to producing Vox amplifier kits for sale in department stores and so on - a sort of parallel to JMI's "Pacifica" kit guitar, introduced in late 1960. Kit amplifiers - presumably the AC2/AC4 or some version of it - evidently never went beyond the planning stage, but Triumph nonetheless handled production of all AC4 chassis subsequently.

Note that Triumph changed the relative positions of the EZ80, EL84, and main filter capacitor on the chassis. New holes - ie. a new design of chassis - were not required though as the components were of the same diameter - i.e. the socket for EZ80 fitted perfectly into the cut-out that had been used up to that point for the EL84.

sn. 2211 - AC4, pink panel, sideways cloth.

sn. 2270 - AC4, pink panel, sideways cloth.

sn. 2394 - AC4, pink panel, sideways cloth.

sn. 2408 - AC4, pink panel, sideways cloth.

sn. 2415 - AC4, pink panel, sideways cloth.

4) From around this point, late 1962, a new taller box comes in. The chassis is fixed to a slider board. Grille cloth has diamonds pointing vertically rather than horizontally. The control panel sits in a full cutaway, rather than an "island". Assembly of the chassis for this final type of beige-covered AC4 also undertaken by Triumph Electronics in Purley.

sn. 2512 - AC4, pink panel, taller box, diamonds upright.

sn. 2585 - AC4, pink panel, taller box, diamonds upright.

By the time we come to serial numbers in the 2900s, we are well into 1963. Below, AC4 serial number 2961, recently sold - components with date codes indicating assembly in Spring or early Summer '63.

AC2 serial number 2961.

Components and assembly

The remarks below, necessarily provisional, are based on sets of images of early amps (to come). Additions, corrections, and so on, will doubtless be required. Resistors are a mix of small 1/2 watt Dubilier and white or green body Erie. The 25uf bypass capacitors are yellow Dubiliers. Signal capacitors are either Dubiliers or Hunts. The main filter capacitor in the preamp is normally a red RTC (a brand of Hunts); in the power amp CCL (at least two amps pictured below) or Hunts again. It is not known at present who made the transformers. The part code for the OT is 18009.

In terms of assembly, the earliest amps are likely to have been made at Dartford Road. As Jim Elyea has indicated, Jim Cole, based in Crayford, a mile or so up the road from Dartford, made the boxes. When chassis and boxes had been assembled at the Dartford Road works, serial number plates stamped by Jack Jennings or his assistant would be added, and the finished amps lined up in the main bulding - number 115 (picture at the head of this page) - ready for despatch.

In late 1961 or early 1962, Triumph Electronics, based in Purley, took over production, probably having been brought in at much the same time as the new circuit diagram was drawn up. Triumph continued to make AC2s, then AC4s, through to end of production. Insulated stand-offs and red RTC-branded capacitors are typical of the chassis that Triumph produced for JMI - see for instance the assembled under contract by the company for JMI.

Below, thanks to Martin Kelly, a copy of the circuit diagram for the AC/2 formerly belonging to Rodney Angell. The sheet, which measures 13" x 8" (old fashioned "foolscap"), is identical to the one designated OS/009 published by Jim Elyea and in circulation elsewhere, but the "OS" number is lacking.

Circuit diagram for the AC/2, no "OS" number.

Early AC2s - late 1960-1962

SINGLE INPUT

Serial number 2020 - currently in the USA

Pictures from Jim Elyea's book. A rare single-input model. Tan rexine, perfboard back, added step-up transformer in cabinet.

Serial number 2027 - currently in the UK

Some preliminary pictures of AC2 serial number 2027, single input. There are no obvious signs that a serial number plate was ever affixed, but the number is stamped on the lower back edge. The original round control knobs are present. One of the little legend plates is missing however. The original perfboard back survives, along with three of its screws, so too the cabinet's metal feet.

At present, the only other known single-input AC2 is serial number 2020, currently in the USA. It is possible that others are still extant - in small number though. Further pictures to follow.

Single input Vox AC2, last third of 1960
Single input Vox AC2, last third of 1960
Single input Vox AC2, last third of 1960
Single input Vox AC2, last third of 1960

Single input Vox AC2, last third of 1960
Single input Vox AC2, last third of 1960

One of the original white print Mullard valves - the ECC83 - with the old-style three-element letter-number-letter factory and date code - "B0K". The "B" indicates manufacture at the Blackburn factory. "0" = 1960; and "K" = November (the months run from A-L). Other valves have "B9D" (April 1959), "BOB" (February 1960), and "BOK" (again, November 1960).

In the preamp, most signal caps and electrolytics have been renewed. In the power section, the main CCL filter cap has the date code "L8" = December 1958. The output transfomer is likely to be an early replacement. Everything else is factory. The Elac speaker has the code "8C/58". On the front of the chassis is "PATTEN" in pencil.

Serial number unknown - currently in the USA

Single input Vox AC2, last third of 1960
Single input Vox AC2, last third of 1960

A single input AC2, serial number unknown. Pictured by J. Elyea, pp. 187 and 403. In company with serial number 2067, the cabinet has had large plastic feet added.

TWO INPUT, BLACK CONTROL PANEL, PERFBOARD BACK

Serial number 2067 - currently in the USA

Pictured in Jim Elyea's book. Two input, black traffolyte control panel engraved with legends in an "island" cut-out, perfboard back. Note the large feet - later additions.

Serial number 2102 - a repro plate of the wrong type

The amp is later, having two vinyl-covered back boards rather than a single piece of perfboard.

NEW

Serial number 2103

In excellent condition. Some components renewed in the preamp as is normal for an amp of this age, otherwise in good original order.

Serial number 2104 - currently in the UK (?)

Before and after pictures of the preamp. The original filter is a CCL (as in 2027), date code December 1958. The Elac speaker has the code 8C/155 rather than the more common 8C/58. The number stamped on the rim is Y16003/18. The output transformer is part number 18009, as in one of the amps below.

Serial number 2137 - currently in Europe

Almost all resistors and capacitors in the preamp renewed, but nicely done. In excellent shape externally. A jack socket has been added on the perfboard rear panel, perhaps for the footswitch.

Serial number 2141

Excellent condition. Electronics original. One of the Dubilier caps has the date code "RC" = March 1960. Perf board back. As above, a jack socket has been added to the back for the footswitch. The Elac speaker has on its frame the stamped codes: "8C/155" and "Y16003/18" (as serial number 2104).

TWO INPUT, BLACK CONTROL PANEL, TWO-PIECE BACK

A page in the brochure issued in Spring 1961 to promote the AC30 with new Celestion blue speakers. The AC2 is depicted as having two inputs, a large logo, black control panel, and grille cloth with diamonds aligned vertically (not horizontally as the amps immediately below). The two-piece back is noted in the description.

Serial number unknown

This amp now has a repro serial number plate (of the wrong type). Two input, black control panel, two-piece back - ply rather than the perfboard of the earlier amps. In the preamp, Dubilier and Hunts capacitors for signal and cathode bypass, and a mixture of resistors. The main preamp filter is a red RTC (Hunts). The main power section filter capacitor is a Hunts with date code "ISD" = 35th week of 1958. The speaker may be a replacement.

By 1962 - the AC2 becomes the AC4

Below, a detail from a typescript JMI pricelist dated October 1961. The AC2 is still the AC2 in an advert published in June.

October 1961

TWO INPUT, NEW PINK CONTROL PANEL, TWO-PIECE BACK, SIDEWAYS CLOTH

Serial number 2211 - currently in the USA (?)

Later in 1962, a new slightly taller box was designed, grille cloth orientated in the normal way.

Serial number 2512.

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