2007 marked the fiftieth anniversary for Vox.
In 1957 Dick Denney brought his handmade 15 watt amplifier to the Jennings Music Store in Dartford, Kent England to show it to his pal, Tom Jennings. Jennings had been dabbling in manufacturing electronic organs for a few years and was very impressed with Denney's amp design. Tom Jennings was looking for new opportunities and products to manufacture. Shortly later, Tom Jennings offered Dick Denney a job designing guitar amps for his new company, Jennings Musical Instruments. Their first amp was called the AC-15, for "amplifier combo - 15 watts."
About the same time, a skiffle band had formed in Liverpool called the Quarrymen. After a number of personnel changes, the Quarrymen became the Beatles. By 1962 the Beatles were playing Vox amps in the Cavern Club in Liverpool. Two years later in 1964, the Beatles were playing Vox amps all around the world, making Vox a world player in the musical instrument business and making their amps some of the most desirable to own.
In 2007 Vox decided to commemorate the early AC-15 by creating the Heritage Collection Series of amplifiers. Vox wanted to recreate some of the circuits that made the early amps great, but also add a modern twist to the designs as well.
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Many feel that the true heart of Vox tone comes from a very simple preamp circuit designed by Dick Denney for the early JMI AC-15 and AC-30 amps. This circuit was powered by the EF86 preamp tube. Unlike the more common twin triode ECC83 (12AX7), the EF86 has higher gain and drive than the 12AX7 and exhibits a unique tonal quality. These EF86 tubes had gotten quite scarce over the years, but once reissued by Electro Harmonix, the possibility of reproducing the original AC-15 circuit became possible.
In addition to the EF86, the Heritage series amps also include three ECC83 (12AX7), a tube rectifier (EZ81 in the AC-15, GZ34 in the AC30) and either two or four EL84 power tubes.
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Channel one exhibits the simplicity of the early AC-15 design. The dual inputs have 6db of difference in level between them. A two position "Bass Shift" switch offers vintage correct bass response in "Position 1" while "Position 2" is voiced to tighten bass response and decrease muddiness. The rotary three position "Brilliance" switch offers flat response in the "Off" position. "Position 1" voices the amp to sound like an early AC-30 "Treble" model amp, while "Position 2" is the original AC-15 "Brilliance" circuit, offering a dramatic bass cut. Finally, the "EF86 Mode" slide switch allows the EF86 preamp circuit to operate as either a high gain pentode or a lower gain triode. |
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Channel 2 is the "Top Boost" preamp channel. Like channel one, the dual input jacks are wired with a 6 db volume difference between them. The "Treble" and "Bass" controls are based on the original 1963 "Top Boost" circuit developed for the AC-30. |
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The traditional rotary "Cut" control cuts treble response from either channel.
The O/P Mode switch toggles the output tubes between "pentode" mode (15 watts on the AC15H1TV, 30 watts on the AC30H2) and "triode" mode (7.5 watts on the AC15H1, 15 watts on the AC30H2)
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