Vox AC-30

The First AC-30?
The First AC-30?

That the Vox AC-30 Twin is a great-sounding amplifier goes without saying, since it spent the past 40 years creating music for countless artists of varying stature and styles. From the king-size extravaganza of Queen’s Brian May and his wall of sound, to the nightclub-filling single-amp assault of the A-Bones’ Bruce Bennett, the AC-30 has done it all.

George and John of the Beatles, Keith, Brian, and Mick of the Rolling Stones, pre-Marshall Eric, Jeff, and Jimmy of the Yardbirds, et cetera; British Rock as we know it came straight out of four EL84 power tubes and two Celestion G12 speakers. But British Rock wasn’t always “Classic,” and the AC-30 didn’t start its life with EL84s and twin speakers.

A promotional package from “The Jennings Organ Co. – Unity Works – Dartfort – Kent” ca. ’59-’60 turned up recently, containing a number of most interesting items. The back of the mailing envelope has the famous triple-trapezoid JMI logo, with “Jennings Musical Industries Ltd., 115-119 Dartford Road, Dartford, Kent,” and “London Showrooms (open all day Sunday), 100 Charing Cross Road, London, W.C.2.”

Anyone interested in the history of the company should read The Vox Story, A Complete History of the Legend, by David Peterson and Dick Denney (published by The Bold Strummer). References will be noted.

Besides the JMI-manufactured Univox keyboard, Jennings organs and Vox amplifiers, the company’s wholesale trade list also included the complete line of American-made Fender guitars, plus Japanese/Guyatone solidbodies (S.P.1 and 2) with the Vox logo, not to mention the “attractive Italian design” Rock-Oval six-string and Oval Basso. Other items included accordions, mouth organs, Jennings saxophones, Vibratone Hawaiian guitars, Hopf hollowbody basses, various microphones, gramophones, tape recorders, and of course, “Domestic Electrical Appliances” such as G.E.C. refrigerators, Morphy-Richards spin dryers, Sunbeam Electric food mixers and Echo “…domestic and industrial lighting fittings, lamps, etc.” J.M.I. was also responsible for accordion and piano pickups, the outboard Vibravox vibrato/tremolo box and a Vox volume pedal.

As for the homegrown music scene at the time (pre-British Invasion), things were pretty dismal in England. Little Richard, Jerry Lee Lewis, Gene Vincent, and other American rock and roll acts were revered there long after their popularity had begun to wane back home. There are numerous stories of young, soon-to-be-famous musicians following Eddie Cochran from town to town. Considering the drivel British record labels were willing to release in the late ’50s, it’s no wonder the thrill-starved kids were going absolutely wild. To get a grasp of the era, try Roots of British Rock, on Sire Records (SASH-3711-2, 1975), compiled by Seymour Stein and containing excellent liner notes by Greg Shaw, an authority on the subject who later published Bomp magazine, as well as offering gems on his Bomp Records label ranging from obscure Bobby Fuller Four reissues to ex-Dead Boys singer Stiv Bators’ venture into power pop (Disconnected, featuring some fine guitar from Georgie Harrison, nee Cabaniss). Some would argue the only worthwhile rock and roll from England at the time was by Johnny Kidd and the Pirates (“Please Don’t Touch,” “Shakin’ All Over,” etc.), which featured the amazing guitar of Mickey Green.
But let’s get back to the AC-30.

A Vox Amplifiers flyer from ca. ’58-’59 was included in the ca. ’59-’60 J.M.I. package, albeit with inked-over prices (for the AC-10, 29 guineas on the flyer vs. 35 on the obviously later price list, 39 gns. vs. 45 for the AC-10 “…with variable tremulant,” 59 gns. vs. 65 for the AC-15 and 70 gns. vs. 79 for the AC-30). All these amps featured TV-front cabinets housing single speakers. Both the AC-15 and AC-30 were equipped with “…the new patented exclusive VIBRAVOX, which is incorporated only in a VOX amplifier, gives three degrees of vibrato and three of tremulant.”

The previously mentioned Wholesale Trade List from ca. ’59-’60 also included both AC-15 and AC-30 Bass Amplifiers (70 gns. and 5 gns.), an AC-6 normal (no vibrato) for 25 gns. plus the brand new 100 gns. “Model AC-30 Twin Amplifier” that would go on to become the longest-running guitar amp of all time, still available today with only minimal changes to the original version of late ’59 (TVS).

Neither the flyer or the price list mentioned The Shadows, who in 1960 became huge stars in England, following the success of their AC-30 Twin-powered version of “Apache.” Jennings referred to them on a list of endorsers accompanying the price list as Cliff Richard Group with no mention of Hank Marvin, their fabulous lead player who would help make the AC-30 Twin the success it became in England. The ca. ’58-’59 flyer pictured popular guitarist/instructor Bert Weed and composer extraordinaire John Barry (with trumpet), along with a handful of accordionists and radio folks. Skiffle hero Lonnie Donegan was listed at the bottom, along with two of England’s earliest rock acts, Marty Wilde and Billy Fury. There was no mention of either an AC-2 or AC-4 in the early Vox literature, though both were discussed in TVS as being available in ’58. Was there an AC-2? Was there an AC-6? Was there an AC-4 with a TV-front cabinet? Readers with any of these should please write, send photos, etc., c/o VG.

An AC-30with two EL34s?
Direct from the late ’50s to the pages of VG comes the lovely AC-30 pictured here – an usual creature, to say the least. First, the covering is a black fishnet pattern over creme leatherette, encasing a TV-front cabinet. The grillecloth has the familiar Vox diamond pattern, although it is slightly different than later variations. A brass Jennings tag, similar to those used on early Rickenbachers, tweed Fenders, etc. adorns the face near the top, while the traditional Vox logo is on the right-hand side of the grille. Unlike later one-piece logos, individual silver letters with red sides were used. There are no signs of this amp ever having the third tag denoting model in the lower/left corner, as seen on later TV front examples. Topping the whole thing off is a hard plastic handle that does not appear to have the strength to be used for its original function. Use old handles at your own risk!

Turn the amp around and things get even more unusual, with a black, perforated fiberboard back enclosing the entire rear, save for 1/4″ of the side, top, and bottom panels around the edge. Similar backs are found on old televisions and HiFi consoles. Stencilled on the back in white letters are “Made in England, Jennings Musical Industries Ltd., Unity Works – Dartford – Kent – England” at the bottom/center, “Warning, Disconnect Mains Plug Before Removing Back Cover,” and “For AC Mains Only, Check Voltage Setting On Back Of Chassis,” on the left and right sides, respectively. Finally, “Serial No.” appears on the bottom/left. There does not appear to have ever been a number applied here, though the number 4052 is stamped into the metal “VOX AMPLIFIER” tag, along with “AC-30.”

Removal of the back panel reveals major differences between this AC-30 and the more famous AC-30 Twin. First, the power supply has its own chassis, mounted to the bottom of the cabinet. The power transformer, a GZ34 rectifier tube, a large capacitor can, and the choke all protrude from the top of this chassis, with wires coming from and going to the second chassis, which is mounted to the top (these wires would include 220-volt AC from the mains switch, heater current for the tubes and B+ high voltage to the plates through the output transformer, which is mounted above). Other wires running to the upper chassis are from the very English power cable jack, installed on the right side of the cabinet as viewed from the rear.

Access to the upper chassis is a nightmare, suggesting the later slide-in tray (that AC-30 Twins have their chassis mounted to) came about as a totally reworked remedy to this poor design, as opposed to simply an improvement upon. Unlike the later design, taking the chassis completely out the cabinet is necessary to access any of the components, although tubes were reachable with a bit of dexterity. Their removal was as far as our bench check got, due to the condition, rarity, and the fact we don’t own the amp.

The tube complement reveals the most important difference between this early AC-30 and later models; twin Mullard EL34 power tubes instead of the usual four EL84s. Depending on how they’re hooked up, a pair of EL34s can put out over 50 watts, so it was decided not to risk the single speaker with a full-power test. Besides, the 220V to 110V converter necessary for U.S. operation was temporarily out of the shop, so there will be no judgemental comparisons of tone. Three ECC83 (12AX7) and one ECC81 (12AT7), all Mullard twin-triode tubes, took care of the other functions, with the ECC81 being closest to the power tubes and probably used for the phase inverter. That would leave one side of an ECC83 for the Vibrato channel preamp, the other side for the Normal channel and the remaining two tubes for the tremolo and vibrato oscillator/modulator functions, assuming they are of similar design to later AC-30s.

Before the ’60s, control panels usually were on the tops (or backs) of amplifiers, with lettering facing the rear. AC-30s are no different. White markings, four input jacks and four knobs on a black panel add a visually interesting contrast to the thin black lines on the cabinet’s off-white covering; not quite op-art, but stylish even today. The knobs are round, with ribs on the side, and a decorative gold ring and black dot on top. Volume No. 1 controls the vibrato channel, Volume No. 2 controls the Normal, and a tone control reportedly rolls off treble from both channels. A Mains On/Off switch, a three-position voltage selector plug (200/210, 220/230, 240/250) and a red pilot light complete the right side of the control panel functions.

It is assumed the first white knob, between the input jacks and the volume controls, switches between three choices of Vibrato Speed (as marked) or tremolo speed, depending on where the Tremulant On/Off switch is set. These functions would be the equivalent of Speed and Vib-Trem on later models. On the original flyer, one can see a black pointer knob, as later used for all control knobs, replaced the white version early on for the speed switch. A footswitch jack for activating the effects requires use of the “Foot On/Off Control,” which is missing, probably due to the fact there was no space provided in the back to store it. The amp does, however, still have the power cable and cover (green with tan piping), both also included in the original purchase price.

The speaker for the AC-30 was not specified in the original flyer, even though the choice for the AC-15 was listed as a 12″ Audiom. No combo amp is complete without a speaker, and the one for this amp says Rola G12 in red letters, similar to the Celestions in pre-’65 Marshalls (see p. 10 of TVS and p. 51 of The Art of the Amplifier, by Michael Doyle), and the later Vox Blues. All of these Alnico-magnet models can be traced to British Rola (which began as an extension of the Cleveland-based Rola Company), which bought Celestion in 1947. For an explanation of why people use the expression “Pre-Rola” to describe late-’60s Celestions, see Marshall, the Sound of Rock, by Michael Doyle. Both books are published by Hal Leonard.

Significance of Early Model
The AC-30 just described, having all the features of the earliest known Vox amps, dates to the halcyon days of J.M.I.-built guitar amps. Inclusion in the ’58-’59 flyer shows the single-speaker AC-30 was not simply a prototype, as suggested in TVS. It’s important to note this was a production model, with stock construction, cosmetic features, appointments for the era, serial and model numbers, etc. Inclusion in price lists concurrent with the AC-30 Twin shows the single-12″ AC-30 was available for at least parts of ’58, ’59, and ’60.

“For the occasion where a really heavy output is required” accompanied the photo of the production model AC-30 (top of the line in the ’58-’59 flyer); the 30-watt amp was available to the public, but obviously considered extravagant by J.M.I. The public’s response apparently was also less than enthusiastic, judging by the rarity of these variants today.

Feature-wise, it offered everything the AC-15 did, plus the lower wattage of the less-expensive model was sufficient to keep up in the bands for which these amps were designed. “Supplies a new vitality to accordion, guitar, bass, piano, etc.” in the AC-15’s description also shows Vox amps weren’t designed specifically for guitar, as has been implied. Remember that Tom Jennings played keyboards and the manager of his London store was a prominent accordionist (TVS); these guys were definitely not rock and roll guitar players!

The questions left unanswered are; where did the two-EL34 circuit come from?; was it the much-hyped Class A, cathode-biased, push-pull circuit?; for how long was it used?; and did the last of the single-speaker AC-30s have four EL84s, and if so, when was the change made from EL34s?

J.M.I. had been building 50-watt amplifiers with vibrato for their Jennings organs in the mid ’50s, and some of the circuit design reportedly went into the TV-front amps (TVS). Many of the pre-Vox organs were fitted with twin speakers, so the technology for the AC-30 Twin was available before Dick Denney came to J.M.I. Someone would have to examine the amplifier sections of pre-Vox organs and the earliest Vox models to see how much circuit design was rolled over. This is not to suggest Denney wasn’t responsible for the sound of the classic AC-30 Twin, just that perhaps others in the pre-Denney era should be receiving credit, as well.

One gent in particular, Derek Underdown, should be mentioned for numerous reasons. He was Jennings’ first amplifier man, starting in ’51. In a press release from ’67 regarding the Queen’s Award for exports, Underdown is noted as head of research, while Denney’s section reads “…guitarist/technician who was responsible for the development of the original and subsequent Vox amplifier series… demonstrates Vox creations at Trade Fairs and Exhibitions all over the world, when he is not working on fascinating new developments and innovations” TVS). Having been written in ’67, while both men were still with the company, should prove Denney’s recollections to be accurate (a rarity amongst musical manufacturers) and Underdown’s role as seminal, important and long-running. He was still with the company long after Denney and Jennings were out of the picture; his nearly 20 years with Vox, including all of the heyday, should gain him a place in guitar electronics lore alongside Bran, Joyce, Tavares, White, Fuller, Lover, Oliver, Hughes, Cox, etc.

Special thanks this month to collector Alan Hardtke for allowing us to snoop around his amp; he would like to thank Steve Melkisethian, of Angela Instruments, for bringing it back from England at a time when few people cared, calling him with the greeting, “You have to have this amp.” Extra-special thanks to my pal John Sprung, of American Guitar Center, for calling on the promotional package with a similar greeting. Also, kudos to photographer John Peden, NYC, for taking this month’s close-ups. All photos used with permission. As for the amp featured here being the first AC-30 ever made, we will have to look forward to response from England to see if it is as prototypical as TVS implies. Until then, or the event one with a lower serial number turns up, Mr. Hardtke can sleep soundly.

Direct from the late 1950s, an usual AC-30 with black fishnet pattern over creme leatherette, encasing a TV-front cabinet. Photo: John Peden.

This article originally appeared in VG‘s May ’98 issue. All copyrights are by the author and Vintage Guitar magazine. Unauthorized replication or use is strictly prohibited.

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