www.proguitarshop.com, The AC15 is the amp that "started it all", as they say, for Vox. It was the JMI (Jennings Musical Instruments) company's first product and a masterpiece of guitar amplification by Dick Denney. Following the AC15's release in 1958, it was quickly became the guitar ( and bass ) amp du jour for Britain's early rock n' roll groups. The Shadows were the most prominent of the early endorsers of the Vox AC15.
The Vox AC15 was instantly popular for a number of reasons. It easily produced the required volume to keep up with drum kits and brass, which have naturally high acoustic output. If one had to push the volume past the point of a clean guitar tone, it would not distort harshly, but would saturate progressively into even harmonic overtones, without generating nasty breakup. In fact, many early rockers found the characteristic ringing, chiming Vox overdrive to be genuinely pleasing. This unique sound was widely exploited a few years later, when English R&B groups of the mid 60's used AC15's to achieve a classic blues tone in recording studios. It's ability to produce a chiming, creamy overdrive at a moderate volume made the AC15 indispensable for recording purposes, and it remains so to this day. A legend was born.
The Vox AC15 Custom Classic series is a throwback to the early AC15's. All the original creamy, chiming tonal qualities that made this amp legendary have been preserved. The AC15CC1X generates 15 Watts of EL84 tube power into the classic 16 Ohm, 12" Vox / Celestion Alnico Blue Speaker ( a rock legend in it's own right). Vox has also updated the amp with a few modern features, including Master volume, global reverb and tremolo controls, and a rear panel 8/16 Ohm impedance selector switch, allowing you to use a wide variety of extension cabinets . It looks particularly smashing with the Vox V212BNX cab, also sporting Alnico Blues. Trem and reverb are footswitchable via the included VF002 footswitch.
By the end of January 1958, the 15 watt Denney twin channel amplifier had been developed to production standard. The styling and presentation were not much different than the classic Vox house style of later years, and it had the first model number allocated to a Vox amplifier, Amplifier Combination 15 watts. Otherwise known as the AC15. A substantial amount of work had gone into restructuring the unit. Denney had built the prototypes on a standard box type aluminum chassis. He realized that while these were fine for tryouts and equipment that would be used in fixed installations, they would not stand up to regular transportation of the kind dealt out in normal use by musicians. The usual way out of problems like these was to use a steel chassis. But Denney's amplifier has a high gain factor, and this presented problems when considering the single common space inside a typical box chassis. Hum and oscillation were commonplace results for such an approach. Steel is much worse in this context than aluminum, having a high earthing resistance and being susceptible to currents induced by the transformers needed in audio equipment. The necessity of a single chassis is peculiar to guitar amplifiers, where the number of interconnections must be kept to a minimum. Vibration is an enemy to plug and socket systems and the separate power amp/ pre amp structures commonly used in hi fi can be treacherous in close proximity to an energetically driven, high output loudspeaker unit.
Denney's solutions was elegant, and was adopted throughout the Vox product range. This was to fix the transformers (heavy laminated iron blocks which cause most of the damage if the equipment is dropped or mishandled) at either end of a strong pressed steel chassis. This also carried supply and power output circuitry, which is relatively insensitive to hum disturbance. The high gain stages of the amp were built onto an inverted L section aluminum folded sheet structure, which was bolted onto the upright rear faces of the transformers. This provided perfect screening of the sensitive input stages from the hum inducing output transformer. The degree of mutual bracing between the two sections for the chassis resulted in a structure of great rigidity which had the strength of steel and the electrical qualities of aluminum in the right places. Interconnections were made only at the insensitive point in the circuit. All the circuitry susceptible to disturbance was in plain view when the rear cover of the amp was removed, making measurement of the components and checking of wiring and solder joints an easy matter, both for the manufacturer and the service engineer. The chassis was fixed down to a strong plywood carrier which could be slid in and out with the rear cover of the amp removed, and the valves could be readily wired up and tested outside the casing, and offered mechanical protection to the valves if it rolled over during inspection of the power section.
Tags: Vox AC15 Custom Classic Combo
