Here are two articles on the AC30 amplifier as used by Brian.

Born to be wild - The Vox AC30 story

Typed in by Matthew Pickles from 'Guitarist' magazine February 1995.
Vox; a name whose enviable heritage can be traced from the very dawn of the 60s beat boom right through to the worldwide renown they currently enjoy. Now, Vox's image is mostly synonymous with the vintage/collectors' market but it shouldn't be overlooked how incredibly innovative and experimental Vox were in their heyday; certainly without their key involvement in the seminal British rock'n'roll movement, most of our favourite bands and records just wouldn't sound the same.

Why Vox played such a vital role is really because they were one of the very first companies to cater instinctively for the guitarist and introduce amplifiers and other products geared specifically towards tapping the exciting potential of the then comparatively new technology of the electric guitar.

Vox's arrival on the scene as interest in electric music soared was no happy accident but was down to a unique collusion between two supremely gifted men, Tom Jennings and Dick Denney.

Tom Jennings

Tom Jennings had run a music shop under his own name in Dartford since the end of World War II and had pre-empted the merger between music and electronics by successfully marketing early examples of electric keyboard instruments, including a peculiar combination of keyboard and speaker system known as the Univox.

As the shockwaves from the USA's rock'n'roll explosion reached Britain during the late 1950's, Jennings found himself besieged by hordes of young British musicians who were desperate to emulate the raw power of Elvis Presley and co and, with typical entrepreneurial aplomb, set about the challenge of meeting the unexpectedly huge demand for electric guitars and amplifiers.

Dick Denney

Tall, genial Dick Denney had been a colleague of Jennings' since WWII when both men worked at Vickers Armaments. During this period, their friendship was cemented while playing together in an ad hoc band entertaining other Vickers employees down the work's bomb shelter during regular visits by the Luftwaffe.

After the war Denney, a talented danceband guitarist who doubled on Hawaiian steel guitar, worked hard developing his own amplifier designs, watched from a distance by Jennings.

While Denney's formidable skill with electronics and Jennings' business acumen seemed perfectly matched, it still took a while before Jennings could lure Denney into a joint venture. In 1957, however, Jennings finally managed to persuade his friend to collaborate on forming a new company. Vox began under the umbrella of Jennings Musical Industries (JMI) and was dedicated to designing and building a new range of home-grown electric guitars and amplifiers.

The company weathered many a storm over the years but passing decades also witnessed Vox constantly experimenting with new products and adapting established ones in an attempt to keep in step with shifting trends in equipment ones in an attempt to keep step with shifting trends in equipment and musical styles.

Today, Vox are distributed by Korg UK, who took over from the previous owners Rose Morris in 1990. While the range of Vox products may have diminished compared to the glory days of the 60s and 70s, the sustained interest in all things vintage has served the company well by enabling them to channel their energies into producing faithful replicas of original Vox favourites such as the ever popular AC30.

AC15, AC10 and AC4

The AC15 was the first Vox to officially roll off the production line in January 1958 and was an instant success. By virtue of its choice of normal and effects channels and built in vibrato and tremolo effects, it offered a hitherto unheard of range of sounds in a compact, highly portable package.

Apart from being incredibly advanced for the time, the AC15 was also exceptionally powerful and eventually became the first amp to feature Celestion's new G12 speaker.

The Shadows were currently heading a huge wave of guitar groups and their adoption of the AC15 set the seal for its reputation as the premier guitar amp of the period, beating off fierce competition from other British manufacturers such as Selmer and WEM in the process.

While the AC15's sleek, purpose built appeal made it an object of desire for all aspiring guitarists, Jennings wasn't slow in realising Vox's need to capitalise on the lower priced end of the market and soon followed up with the AC4 and the AC10.

Both amps were simpler and slightly less rugged than the AC15 but sold in equal numbers thanks to their more affordable price. The AC4 was the smallest and most basic model which offered an earth shattering four watts of power through a single six inch loudspeaker before Vox revised the design to include a single eight inch Elac speaker. The AC10 was closer in appearance and output to the AC15 but lacked the vibrato circuitry and early models used a single 10" speaker before changing over to a more efficient pair of 10" units later in 1958.

One of the major factors which made the AC15 such a distinctive amplifier was that it didn't owe its design to the Fender amps of the period and was an entirely original concept from the ground up.

It is difficult to condense Dick Denney's technical genius but in a nutshell, he decided to base Vox's circuitry on EL84 output valves for their propensity to produce a good power level with a relatively low distortion threshold. Denney discovered that under most normal circumstances (hi-fi manufacture, for example), an amp using EL84s would employ a process called negative feedback (NFB) which restricted the output valves' distortion limit in order to produce the cleanest possible sound. By dispensing with NFB altogether, Denney was able to fully capitalise on the EL84s in 'cathode bias', a relatively simple load compensating mode which used less components, the final result was remarkably strong, clear and harmonically sensitive sound.

Thanks to the AC15's naturally broad and poky quality, the amp required little in the way of a tonal leg up and consequently didn't require particularly sophisticated tone circuitry to make it work properly, a feature which can still characterises Vox amps today.

The AC30 arrives

The birth of the AC30 was precipitated by the more successful groups' need for more and more volume. As rock'n'roll became the staple diet of young people the length and breadth of the UK, the demand for groups meant that bands were now able to perform in venues such as cinemas and dance halls in front of audiences numbering anything from 600 to more than 1000 - a far cry from the tiny cafes and coffee shops where acts like The Shadows and Tommy Steele had cut their teeth.

Powerful as it was by contemporary standards, the AC15 couldn't meet the needs of a guitarist or bass player battling to be heard over a drummer, who was himself struggling to compete with the screams and shouts of an audience of 500 plus.

At first the only viable alternative to the AC15 came in the shape of Fender's Twin amp, a hefty 60 watt, 2x12 combo. Unfortunately, the Twin was not only in short supply but the shipping and customs duties added up to a frighteningly prohibitive price tag and while groups like The Shadows has expressed a liking for the Twin's volume, they felt that the Fender couldn't compete with the Vox on tone. Acting on the logical thought that a 'twin' AC15 was the answer, Dick Denney set about building a bigger and better amplifier. After experimenting with an unsuccessful prototype AC30 with a single 80 watt 12" Goodmans speaker, Denney decided on an improved version whose larger dimensions were compensated for by a pair of lightweight, 12 inch, 15 watt Goodmans.

The Shadows walk in

The Shadows played an invaluable role helping Denney to perfect the new Vox amp by undertaking a rigorous research and development schedule and reporting back to Denney, who often travelled with the band to assess their impressions of the amp.

Ironically, the AC30 played almost as important a role in The Shadows' rise to success as the group did in helping the amp gain wider acceptance. The AC30's greater power and clarity helped the group gain in confidence to the point where they felt they now had the necessary equipment to venture out as an instrumental band in their own right. Armed with a Fender Stratocaster, a Meazzi echo unit and the new AC30/4, The Shadows had what amounted to the finest state of the art equipment and used it to devastating effect, not only inspiring a massive wave of instrumental groups but also putting Vox's name on the map as the amplifier to own if you were a serious musician.

With The Shadows' seal of approval, Vox put the AC30 into production in late 1959 with the group taking delivery of three of the earliest models, although the AC30 didn't really become widely available until 1960.

Original examples of the AC30/4 featured four separate inputs, a light tan covering, a brown latticed grille cloth and a new moulded, one piece emblem in gold which aptly demonstrated Tom Jennings' intuitive talent for cultivating an eye catching and highly recognisable image for his products.

The AC30/4 benefited from a final tweak when it ditched the original Goodmans Audiom 60 speakers in favour of a pair of modified Celestion G12s. These new speakers coat of dark blue cellulose and distinctive rounded magnet cover rapidly lent them the tag Vox 'blues' and their crisp, accurate response set an industry standard in guitar speaker manufacture which other companies still struggle to emulate.

Beatles and bass amps

Like the Shadows before them, The Beatles' association with Vox began in earnest in 1961 when the Fab Four purchased couple of AC15s prior to embarking on their legendary nightclub residency in Hamburg. The Beatles had chosen Vox as a direct result of their respect for The Shadows, who were rightly viewed as the premier hi-tech band of the era, and it wasn't long before they too moved up to the bigger and more flexible AC30.

Brian Epstein procured The Beatles' first AC30s from Tom Jennings' shop in Charing Cross Road just before recording started for their first album 'Please Please Me'. The Beatles stayed loyal to Vox long after they quit touring but it was during their epic stints on the road that they too played an important role in helping Dick Denney and Tom Jennings steer amplifier production in a whole new direction.

Bass guitar amplification wasn't really taken seriously until Vox developed the T60 bass amp and, in doing so, developed the first transistor powered amp to achieve success on a wide scale. Even though reliable solid state components were still in their infancy, Jennings was determined to be first out of the gate with a reliable transistor powered amp and instructed Dick Denney to not only make the amp as practical and reliable as possible, but also as compact.

Denney achieved this fairly easily and also devised a highly unusual cabinet to accompany his new amp which contained 15" and 12" Celestion speakers in tandem, with a special filter unit feeding the 12" to prevent damage from cavernous bottom end frequencies.

Towards the end of The Beatles' touring life, Paul McCartney used the T60 to great effect both home and abroad, and its popularity spread, which tends to scotch ugly rumours from some sources about the T60's tendency to be unreliable!


Oddly, the AC30/6 was originally developed as a temporary stepping stone between the four input AC30 and a planned range of dedicated bass amplification, but it survived to become probably the most widely used AC30 variant of all.

With the increasing popularity of the electric bass guitar, Vox were soon looking to increase the AC30's suitability to the new instrument.

AC30/4s used by bass players tended to suffer from mechanical damage caused by increased low frequency vibration and in response, Vox redesigned the AC30 to include a third channel. Labelled 'brilliant', this extra channel graced the AC30 with a third pair of high and low sensitivity inputs by replacing the normal channel's vibration prone EF86 single pentode valve with a less costly but altogether tougher ECC83 triode valve.

Now the AC30 could happily accommodate two musicians at once and the most common combination usually saw a single AC30 shared by a bass player and a lead guitarist - although vocalists, harmonica players and even some keyboard players didn't miss the opportunity to buddy up when they could get away with it.

The top boost

Vox's decision to upgrade the AC30 with extra treble circuitry marked what was probably the last and most significant variant on the original AC30 design.

The decision was instigated in 1961 at the behest of - yes, you've guessed it - The Shadows who eventually decided that they did like the Fender sound after all and wanted to approximate the sound through one channel of their amps. Dick Denney undertook the development work and came up with the improved circuitry in the form of an L shaped plate which could be wired in to the amp's brilliant channel at the factory or mounted by anybody who could wield a soldering iron. The add-on unit was comparatively simple and comprised two controls; one for bass, one for treble and an extra ECC83 twin triode valve. Despite its comparative simplicity most customers didn't have the technical knowledge to fit the new circuit and consequently the Top Boost, or 'Brilliance Unit' as it was officially named, was fitted to the AC30 as standard from 1964.

The extra gain and tonal variations offered by the new circuitry literally 'boosted' the amp into a whole new sphere of popularity and its gutsy sound provided an ideal weapon for the rapidly rising crop of rough and ready rhythm and blues bands, headed by The Rolling Stones and Manfred Mann.

Radio days and the end of an era

Vox's pioneering spirit wasn't strictly confined to producing amplifiers. Dick Denney deserves due credit for his unique sense of vision - a gift which occasionally bordered on the eccentric but always displayed an uncanny knack for predicting some of the electronic devices we take for granted today.

One of these isn't widely known about but aptly illustrates Denney's flair for the unconventional. The Vox radio microphone was one of the very first attempts to develop a cordless guitar system and was designed in conjunction with Reslo, the microphone manufacturers who regularly supplied Vox with spares. Probably the most famous users of this system were a bizarre Scandinavian instrumental group called The Sputniks, who regularly took to the stage wearing silver spacesuits, Perspex helmets and whose music displayed an equally strong science fiction slant.

With typical attention to detail, Denney offered the cordless mike in two setups; type S was aimed at the soloist and is generally regarded as the better unit due to the improved performance of its wider frequency bandwidth, while type C had a maximum of four separate transmitter tunings and was primarily designed for groups. Technically, it wasn't too far behind the radio systems common today and why it never caught on is still a mystery.

In the end, Vox's need to keep one step ahead of the game led to the beginning of the problems which beset the company, even in the booming mid 60s. The continuing advances in solid state technology led Vox to believe that the days of the valve amp were numbered and so in 1963 Tom Jennings took the decision to phase out the original valve models and replace them with a range of transistor amps built in conjunction with the Thomas Organ Company of the USA.

Jennings' decision was largely influenced by the realisation that a collaboration with an American company would vastly ease the job of meeting the USA's rising demand for Vox equipment and so a deal was struck which saw new models being built in both countries and distributed according to local needs. The only important differences between the American and British Voxes centred on the speakers; by 1967, the Celestion G12 was being discounted and so UK models received Goodmans' ceramic magnet loudspeakers while American build versions used a good quality G12 copy built in Canada.

Just as Vox seemed poised on the brink of world domination, events took a course which were to lead to the eventual dissolution of the original team and the beginning of the end of their reign as undisputed market leaders. A year after the Vox/Thomas Organ tie-up, Tom Jennings decided to share ownership of the company in an attempt to generate funds to match the USA's ever increasing demand for Vox goods and, in June 1964, Vox became part of the Royston group. Unfortunately for JMI and Tom Jennings himself, circumstances dictated that Royston acquired a majority share and in doing so effectively removed control of the company from Jennings' hands.

Despite the honour of receiving the Queen's award for Industry in honour of Vox's achievements, Jennings found himself repeatedly frustrated and disillusioned by the changes he saw happening around him and tendered his resignation to Royston's board of directors in 1967.

By this time Vox had also lost vital ground at home and abroad to a new British amplifier maker, Marshall, who had a virtual monopoly with the new hard rock acts of the period, such as Jimi Hendrix, Cream and The Who; Vox's star had begun to decline.

Even the easy going Dick Denney was eventually exasperated enough to follow Jennings' example and both men eventually went their separate ways, never to work together again.

Tom Jennings passed away after a stroke in 1978 but the irrepressible Dick Denney eventually renewed his ties with Vox in 1990 and even though he is now retired, he remains actively involved in both music and electronics.

Extracts from:

The Vox Story by David Petersen & Dick Denney

typed in by by Gonzalo Plaza R.
by Brian May

My adventures with Vox began in the second-hand shops in Wardour Street around 1967. I had an image of exactly how I wanted my guitar to sound, but had never quite achived it. I had come close by plugging in to my father's homemade hi-fi amplifier, but seemingly further away using the various combo amps that were available. I was lucky to have a fair understanding of what was going on inside these amplifiers, thanks to my father, an inspired electronic engineer, who had helped me design my own guitar a few years earlie. What I wanted was a guitar amplifier which would sound clean and bright at low levels of amplifications, but smoothly slide into the kind of distortion which on a single note didn't sound like distortion but more like a violin. Transistor amplifiers, althought they were extremly good at producing faithful results at low volumen, did not fit the bill for producing the "saturated" sound. When the volume was turned up, they immediately went into violent and unpleasent distortion. The large valve amplifiers of that time, such as Fender and Marshall, produced a violin sound once distortion was entered. Missing was the intermediate range where there was still some clarity, but these extra harmonics were creeping in. Having briefly tried out an AC30 belonging to one of my friends, I was convinced that this was "it". The Vox AC30 was, and is, one of the very few amplifiers which uses Class A configuration. The quality at low levels is broad and crisp and unmistakably "valve like", and as the volume is turned up it slides very controllably into a pleaseant creamly compression and distrotion. From the moment I got the thing home and plugged into it, it was love! To achieve the bigness of sound that I wanted, it was essential to eliminate the unpleasent intermodulation distortion between straight signals and effects. So I found myself buying another AC30, and yet another, for the two delays which I was experimenting with on stage. As the places that we played grew i size, so did the array of amplifiers and I ended up with an array of 12 of these beauries, a very comforming "stack" to stand in front of. In the very largest places of course, monitors are all and so it is quite possible to revert to a single amplifier, fed through the whole set of monitors, to the point where it can be heard all over tha stage and where that vital feedback mechanism can take place, that being the mechanism which really makes the notes "sing".

Like musical instruments themselves, every guitar amplifier, and certainly every AC30 has little quirks which give it its own character. The great advantage of these machines is the fact that they are rugged. In the event that a valve does give out, another AC30 can be "wheeled in" to give an equally good effect. There have been many different versions of the AC30 and of all the other Vox amplifiers. But I have found that much of the mystic factor is in people's minds. The new AC30s, which I am using at the moment, have just as much charcter as the ones that date back to the mid-1960s. It's nice to find that the quality and the magic are still there.

For anyone who has come in the contact with the Vox legend, which includes guitars, organs and many other accessories, this book provides a fascinating insight into the development of a small company with the big ideas a truly innovative designer, and a succession of great teams. Here's wishing Vox a future as colorful as its fascinating past.

(Photo of Brian with the Red Special and the 12-Vox AC-30 wall)
(Signed Brian May, Queen 1990)

Chapter 8 (page 95)
After the Fire (1972-1978)
Brian May and Queen

This survival meant the acquisition of its most important endorser in recent years, Brian May of the group Queen, whose guitar sound, helped by the use of multiple AC30s, became one of the most effective and influential of the decade, and presented the AC30 in a new and dynamic context. Good examples of his individual, higly melodic style can be heard on such tracks as "Bohemian Rhapsody" and "Killer Queen", while his formidable array of AC30s, typically numbering between nine and twelve, showcase the amp's styling and provides powerful promotion for the Vox name whenever the group goes on tour. (Other text)

(page 97) full page photo of Brian with a Guild '84 BHM1 and siting over a Vox AC30) Brian May in the British Music Fair 1985, with the Guild guitar bearing his name. Visible by his left hand is the treble booster he is accustomed to using with his Vox system. (Photo Coutresy of Mark Smith).

(page 108) The second was the chart success of Queen in 1975, who used AC30 amplifiers in a radically different way to anyone previously. Brian May's sound relies on the dynamic, touch-sensitive characteristic of a "wide-open" AC30, with enough of them to produce an acoustic interaction between the amplifier and the guitar, rather like Hendrix had done with his Marshall amplifiers, but with far greater finesse. May's example inspire many groups to use Vox again, the most important of whom changed over from Marshall. Status Quo used the Brian May-insipred multiple-AC30 system after 1976, although their musical style was completly different.

Appendix 4
Facts and Fancies

Brian May's Vox System

(page 148) The foremost exponent of the AC30 is without doubt Brian May. In this book's introduction, he clearly describes the evolution of his system from a basis of two ampilifers, one for straight sound, one for effects. The natural sonic virues of the AC30 are also too well evoked by him to need more description. An intersting detail is that he does not use the brillant channel of his amplifiers as would the great majority of guitarist, preferring instead to drive the normal channel with a treble booster made for him by John Deacon, Queen's bass player. This reportedly based on the single-transistor circuit of the in-line Vox device of the mid-1960s, housed in tougher case. The advantage of driving the AC30 in this way is that the tone controls of the brillant channel are not in the signal path. These introduce considerable phase-shift between frequency bands, which results in both electrical and acoustic cancellation. The audible effect of this is to shorten sustain, which would not be at all desirable for the type of sound May creates. The amplifiers are used at maximum volume setting and controlled by guitar setting and footswitch selection. Originally Gibson Echoplex units were used to generate the repeat echo needed in May's trademark "layered" solos. These were substantially modified by May himself, clearly no mean technican, the most unusual change being the separation of the direct and the echo return signals to their own amplifiers, as opposed to summing them and providing a mixed output signal in the conventional way. With May's more recent digital-delay system, threee differently timed returns go to three separated amplifiers with another amp for the direct signal, four in all. May is a guitarist with a wealth of practical experience, and knows that an hour of treble-booster overdriving can punish the toughest amp, so to avoid any possibility of interruption due to amp failure (remember, he's the only guitarist) another two sets of four AC30s are patched into the custom-built switching signal-router, one of which is kept running for "seamless" switchover. The third is fired up only when the second set is in use. The 12-amplifier array has become a trademark of Queen's stage show and an impresive reminder of excellence of the AC30 in meeting the demands of one of rock's most dynamic and accomplished players.