"Melody Maker" magazine, 8th March, 1958. Bulletin no. 3 of the JMI Electronics Division.

Initial design (late autumn 1957)

The first design was modular in nature. The chassis could be removed from the wooden case and used separately as a "cage" amp. It appears that the same was intended initially for the AC1/15, though there is no evidence at present to suggest that this went any further than the planning/prototyping stage. At any rate, no AC1/15 has ever been spotted in a tall case. When the AC1/15 did finally appear in early 1958, its control panel was substantially wider than that of the AC2/30, its box almost square in format and with a TV Front. Thanks to Glen Lambert for his analyses.

The images above and below are scans from a copy of the catalogue made in the 1990s. Thanks to Mike for the pics. The text above has been renewed, following the original. The image of the AC2/30 as cage amp was probably flipped at some point on its way to print in 1957. The control knobs should be on the right-hand side as it faces us.

Note the last line: "The amplifier, which has two chromium lifting handles, is in silver grey, hammered finish".

One of the accompanying price lists - "Deferred Payments".

Production (late 1957 to mid 1959)

The amp came in two varieties: the standard model with four inputs, lacking Vibravox; the other with six inputs, Vibravox built in, the additional two inputs being for the Vibravox channel. Descriptions in the adverts (see below) occasionally conflate the two.

The earliest dated reference that has come to light for the single-speaker AC2/30 is a piece by John England, "Accent on Amplification", published in the music trade press, October 1957. It seems likely that the amp was ready in some form for the round of Trade Shows in August of that year.

Music trade press, October 1957.

Note that the design as outlined above seems only to have encompassed three inputs - but that may have been shorthand for the three channels of the vibravox version of the amplifier.

The speaker was a 15ohm 12" unit - probably a Goodmans Audiom 60. See the "Melody Maker" advert for 22nd February 1958, below.

The amplifier's control panel was black and the knobs white. The cabinet had a split front with diamond grille cloth fixed horizontally. There was a cut-out on top of the cabinet for the control panel and a vent to dissipate heat from the valves. A solid luggage handle was fixed to the cabinet's right-hand side.

Approximate dimensions: around 22" tall; 14 1/2 to 15 inches wide (the AC2 of late 1960 was 14 1/2 inches wide); and 10 1/4 inches deep. The control panel looks to have been about 12 inches long.

The AC2/30 was a sort of multi-purpose amplifier - aimed at accordionists, lap-steel players, and guitarists. It was taken up by a number of famous musicians: Jack Emblow and Henry Krein were both pictured with one, Bill Kent, and Bert Weedon (no pictures of the latter at present). Dick Denney also used one at the Embassy Court ballroom in Welling. See this page.

Judging by the advert above, Jennings was evidently proud of the built-in vibrato/tremelo - "gives such a startling effect that tape recordings have been made and will be sent on request...". The circuit diagram for the AC2/30 is OS/003.

JMI circuit diagram - UNDATED - "AC.2 30Watt Amplifier. OS/003." An octal socket was provided for the plugging in of an external Vibravox unit or a Radio Tuner. The complement of valves is: two ECC82s (12AU7) in the preamp; two EL34s for output; and a GZ34 rectifier. The EL34s have around 400v on their plates, and a fixed bias of -30v. Thanks to Glen Lambert for the image.

Mike, who supplied the pictures at the top of this page, is a member of a select group - those who recall working on an AC2/30 (to repair). He said: "They were much bigger and heavier than the pictures suggest. Don’t forget there was a 12” speaker in there. Slotted hardboard radiogram type back panel."

Two adverts issued in June 1959 show that the AC2/30 was still available. The one below explicitly mentions it, the other gives the two prices - 62 and 70 guineas - prices that had been set in March 1958.

June 1959.

"Melody Maker" magazine, 16th November, 1957, and detail. 55 gns for the standard model, 62 gns for the model with vibrato (vibravox). The logo takes this form on the amp illustrated in the "Accordion Times" advert, December 1957, page 31, below.

"Accordion Times", December 1957, page 24. The logo is of the same form in the advert in "Melody Maker", 11th Jan. 1957, below.

"Accordion Times", December 1957, page 31. As in the "Melody Maker" illustration above, "VOX" in large letters diagonally across the upper panel. The four controls indicate the amp is a standard model - two volumes, one bass, one treble.

"Melody Maker" magazine, 11th January, 1958. Bulletin no. 1 of the JMI Electronics Division. The AC2/30 is last in the row of thumbnail sketches.

"Melody Maker" magazine, 22nd February, 1958. The prices are still 55 gns (standard), 62 gns (vibrato).

"Accordion Times" magazine, March 1958.

A detail from a double-page Jennings spread, March 1958. The amp is said in this to have six inputs. Other early sources (see above and below) sometimes say either three or four. The operating voltage is given as 200v/215v. These were either settings in the 110-250v or 200-250v operating ranges stated in other promotional material, or a misprint (for 200/250v).

Detail from the reverse of a flyer for the AC/15, early 1958.

Detail from the reverse of a flyer for the AC/15, early 1958. Note the large VOX letters, also seen on other AC2/30s but arranged diagonally in the upper panel, and the stylised foliage background of the panel itself. This amp apparently had two bronze "Jennings" labels - one underneath the VOX logo and one on the side.

"Melody Maker" magazine, 12th April, 1958, and detail.

"Banjo, Mandolin and Guitar" magazine, May 1958. The series of JMI Bulletins is different from the one published in "Melody Maker" magazine.

Raggett's Hall, Maidstone, 1958. The "VOX" logo has gone, but the small plaque underneath - "Jennings" (?) - remains.

"Accordion Times" magazine, February 1959. The Francis Wright Quintet.

For further pictures of the AC2/30 in use on stage (venues in Kent) in 1957 and 1958, see this page. It has been ventured that "only a handful were made". This may need to be revised as at least 5 different ones are captured in contemporary photographs.

JMI descriptions

MELODY MAKER, February 1958 (above): VOX AC2 AMPLIFIER 55 gns. A 30-watt output at 15 ohms, A.C. mains operation Hi-Fi amplifier, fitted with three input sockets: (a) for crystal mikes, (b) for ribbon-moving coil mikes, (c) for gramophone pick-ups, radio tuner units and high level signal inputs. There are two volume controls for inputs (a) and (b), and one volume control for input (c), in addition to separate bass and treble controls. (Fitted with internal vibrato. 62 gns.)

3 inputs, 3 volume controls, 2 tone controls (bass and treble). Note that the amplifier in the descriptions below has PAIRS of input sockets. There is no explicit mention above of guitar or bass.

ACCORDION TIMES, March 1958 (above): "Vox Hi-fi Amplifier AC2/30 has 30-watt output; A.C. mains, 12in. heavy-duty speaker; three pairs of input sockets, each with its own volume control, also two separate overall bass and treble controls. Standard model: 62 gns. Fitted with internal vibrato: 70gns."

The 6 inputs, 3 volume controls, and 2 overall tone controls (bass and treble) evidently describe the Vibravox model. The vibravox circuit presumably required a further control on the control panel, bringing the total to 7.

Detail of the Vibravox from "Accordion Times", March, 1959.

JENNINGS CATALOGUE, 1958: "Vox Hi-fi Amplifier AC2/30. 30-watt; A.C. mains (200v to 250v), with four high-inpedance input sockets - two for use with crystal mikes, guitars, electro-bass, accordions etc., and two for use with guitar, electro-bass, radio-tuner units, radiograms and recorders. There is a volume control for both pairs of inputs, also two separate bass and treble controls. The amplifier is housed in a robust case fitted with a 12-in. heavy duty loudspeaker and also, if required, a VIBRAVOX unit."

4 inputs, 2 volume controls, 2 tone controls (bass and treble) describe the standard model.

ADVERT, March 1958 (below). The amp is said to have 6 inputs, 3 volume controls, and controls for treble and bass. The voltage options 200/215v stated may be an error for 200/250v.

March 1958.

On to the single speaker AC/30 - 1959-1960.