The Beatles Vox AC-50 Mk I "Washington DC Amplifier" - 1964


The AC50 Mk I amplifier played a crucial role in the process that led Vox to become a world wide leader
in guitar amplification equipment. The story of the development of the AC-50 starts in 1963.

Vox started to investigate the development of high powered amplifier circuits in early 1963. JMI had no model in the 80 watt power range of the Fender Showman, an amp 50 watts more powerful than anything offered by Vox at the time. In response, Vox started development of both a 50 and a 100 watt guitar amplifier.

Additionally, JMI doubtlessly became aware that the maximum output of the Vox AC-30 amplifiers used by the Beatles was no match to the sound of their screaming fans. Might it be possible that the Beatles could jump ship from Vox to Fender's louder amplifiers? JMI knew that more powerful amps were needed soon.

Vox decided that the major selling feature of these new amps should be their abundance of power, not the inclusion of effects or multiple channels. Neither the complicated Vox Vib/Trem circuitry or reverb would be included in these new amps, leading to a production cost reduction. A higher power rating could justify a higher retail price over the AC-30. The new amps would be simple, uncomplicated, loud and profitable.

Lead Vox engineer Dick Denney recalls on page 47 of his book, "The Vox Story," that Triumph Electronics, an AC-30 chassis subcontractor for Vox, developed a 50 watt power amplifier circuit powered by two EL34 power tubes that might be suited for use in a new Vox amplifier. When this 50 watt, Triumph designed power amp was combined with the "top boost" preamp and tone circuitry from the AC-30, the new AC-50 Mk I head was born.

With the Beatles in mind, Vox hurried the first AC-50 amps to completion. Vox enlisted a modified an AC-30 speaker cabinet to accompany the new AC-50 head. This cabinet would be covered, full face, with brown Vox grill cloth. This cosmetic was a departure from the split vinyl/grill design used on all Vox amps since 1961. This cabinet has been nicknamed the "small box AC-50 speaker enclosure."

The new AC-50 head was compact and powerful, but failed to achieve the brilliant top end response players loved in the Vox AC-15 and AC-30 amps. Vox addressed this issue by adding a Goodmans Midax horn and crossover to the new small box AC-50 speaker enclosure they intended to provide to the Beatles.

The AC-30 speaker enclosure was not deep enough to enclose magnet assembly of the Midax horn. Vox decided to simply cut a hole in the back of the cabinet and allow it to protrude about a half of an inch from the back of the enclosure. A deeper AC-50 speaker cabinet design would remedy this issue in later production.


In addition to a Goodmans Midax horn, the cabinet also featured two Vox Alnico Blue loudspeakers, manufactured by Celestion.

There is no evidence to support that Vox ever offered this cabinet, including the Goodmans Midax horn, to the general public. However, Vox did offer the "full face" grill AC-30 cabinet, less the Midax horn, in their 1964 catalog.

The Vox AC-50 "small box" amplifier became historically significant when George Harrison and John Lennon each took delivery of an amp several weeks prior to the Beatles first appearances in America in 1964. While not visible to the television cameras, these heads and cabs were played by the Beatles on the February 9, 16 and 23 1964 performances on the Ed Sullivan Show. The Beatles also played a concert using these amps at the Washington Coliseum in Washington DC on February 11, 1964 (see photo at left). This concert was filmed and has been subsequently released in DVD format by Apple.

Over the years, this first version of the AC-50 amp head and accompanying "small box" AC-50 speaker enclosure have come to be known as the Vox "AC-50 Washington DC Amp."

The amps also make an appearance in "A Hard Day's Night" during the performance of "If I Fell." At the 1:36 minute point in the clip from "A Hard Day's Night" shown at the bottom of this page, George Harrison nearly knocked his small box AC-50 speaker cabinet from the rigid stand. Paul McCartney's 2x15" AC-100 bass cabinet is also seen at 0:39 minute point.


For their June 1964 performances in Hong Kong and Australia, Vox replaced the rigid stands that had originally supported the Beatles' AC-50 small box speaker enclosures with a new swivel stand (seen at right).

The AC-50 Mk I amplifier head was supported by a single tube that rose from swivel mounts on each side of the cabinet. Later Vox swivel stands were designed so the head rested on dual parallel support tubes.

These new stands were not only attractive, they allowed the speaker cabinet to be tilted for best dispersion and provided easy access to the volume and tone controls.

Vox produced a similar swivel stand for Paul McCartney's 2x15 AC-100 bass amplifier.

Very few AC50 MkI and AC-100 Bass swivel stands were produced by Vox, but North Coast Music produced reproductions of both.

In retrospect, the original AC-50 "small box" amp and speaker cabinet served Vox by keeping the Beatles as Vox artists, and by doing so, helped to create a world wide mania for Vox products.







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Photos and editorial content courtesy Gary Hahlbeck, North Coast Music


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