The worst nightmare for Vox came in the form of a phone call from the Beatles in December 1963.
The Beatles were on the verge of becoming a world wide pop music phenomenon. Beatlemania was in full swing in the UK and spreading throughout Europe. The Beatles would be performing in less than six weeks on the "Ed Sullivan Show" in the United States, making the Beatles the first British music act that would significantly penetrate the lucrative American market. The Beatles played Vox amps exclusively, and Tom Jennings, the owner of Vox, was expecting a large surge in sales riding the cresting wave the Beatles were creating. All looked rosy for Vox until the phone call. The Beatles reported to Vox that the AC-30s that had powered their guitars through their rise to pop stardom were no longer loud enough to cut through the din of screaming girls in their audiences. They needed louder amps, and Vox was unprepared to answer their request.
To make things even worse, Tom Jennings' company, JMI, was not only the manufacturer of Vox amps. JMI was also, incredibly, the UK distributor of Fender. I suspect that the Beatles would have been happy to accept Fender Showman amps in lieu of staying with Vox.
Tom Jennings and his head engineer, Dick Denney, went to work on the problem. They contacted Triumph Electronics, the British electronics subcontractor that Vox had retained to produce their amplifiers about the problem.
Triumph proposed a solution that seemed feasible. Triumph had just finished the development of a 50 watt amplifier with two EL-34 power tubes for the British hi-fi marketplace. It was suggested that a new higher power Vox amplifier model could be created by combining the "top boost" channel preamp circuitry from the AC-30 with this new 50 watt "hi-fi" power amp from Triumph. This concept grew in favor with Vox for a number of reasons. The new amp could be developed quickly. Tonally, it would utilize the time tested AC-30 top boost preamp circuits. Finally, like the AC-30, the new amp would have a cathode biased (Class A) power amp circuit, this time replacing the EL-84 tubes in the AC-30 with higher powered EL-34 power tubes.
Vox modified prepared a specially modified AC-30 speaker cabinet for use with the "small box "AC-50 head.
