Jennings AC40

August 8, 2006

In 1967, Vox founder Tom Jennings was feeling the full impact of having lost controlling interest of his company to the Royston Group—a British industrial holding company—while also being forced to watch helplessly as Vox’s U.S.-based partner, Thomas Organ, was calling questionable shots in the design of Vox amplifiers. The push by Thomas to convert the line to solid-state, while simultaneously discontinuing the use of the essential Celestion Blue speakers, had helped to greatly diminish Vox’s standing in the American

market. These factors, coupled with Royston’s decision to pursue the costly development of transistorized flight data recorders—leaving little capital to invest in Vox at a time when it was needed the most—created a rather dire situation, to which Jennings responded to by resigning from Royston’s board of directors in September 1967.

Jennings and his longtime friend/chief amp designer Dick Denney (who also resigned from Royston) quickly re-established themselves at the original Vox headquarters in Dartford Kent, and set about creating a new company called

Jennings Electronic Industries. Among the first JEI products were a pedal called the Cyclone, and a primitive synthesizer named the Bushwacker— the sounds of which Denney described as being similar to “croaks.”

Denney was tasked with designing amplifiers for JEI, and, having earned worldwide acclaim for his AC30, was undoubtedly eager to develop a similar combo for his new company. What he came up with was essentially a redux of the AC30, which was dubbed the AC40.

Though the Jennings AC40 bears a resemblance to its Vox predecessor, its top-mounted controls are accessed from the front instead of the rear. Both amps feature three pairs of input jacks, although the knobs are arranged quite differently on the AC40, with the Vib-Trem controls grouped on the left side of the panel, the Normal Volume in the center, and the Brilliant Volume, Bass, and Treble controls on the right side. The AC40 has no Cut control, as found on the AC30, but its Bass and Treble controls are AC30-style Top Boost circuits. (Worth mentioning is that both amps produce an output signal that is out of phase with the input signal when using the Brilliant channel. The input and output signals are in phase, however, when using the Normal or Vib-Trem inputs.)

Jennings used many of the same contractors and parts suppliers that he had for Vox, which helps explain why the metal back-panel labels look virtually identical on the AC30 and AC40, and also why the AC40 sports a pair of Vox-labeled Celestion alnico speakers, which bear the following designations: “Designed for JMI Sound Equipment” and “Jennings Musical Industries, LTD, Dartford Road, Dartford Kent.” The AC40’s cabinet was likely made by the same outfit that did the cabinetry for Hiwatt, and is equipped with plastic side grips instead of the trio of top-mounted handles found on the AC30.

Given the preponderance of similarities between the two amps, it’s no wonder they sound quite alike. While our test model was a little more aggressive sounding than a reissue Vox AC30 (equipped with Celestion Blue speakers) we used for comparison, the signature top-end sparkle and harmonics-laden upper midrange was equally well presented by the AC40. The lack of a Cut control (which attenuates highs at the phase inverter stage) is only of consequence when using the AC40’s Normal or Vib-Trem channels, and is far outweighed by the dramatic sweeps of the highly interactive Bass and Treble controls on the Brilliant channel. Jennings and Denney had a winning formula with the AC30, and must have felt no need to reinvent the wheel, so to speak, when designing the AC40. Indeed, Jennings’ version remained more true to original spec than many of the AC30s that were made during the years that Vox was undergoing regular changes of ownership

Unfortunately, JEI would be the final partnering for Tom Jennings and Dick Denney. The company folded in 1973, and Jennings (who had resigned a year earlier) went into semi-retirement—though he remained a consultant for Vox during the period it was owned by CBS-Arbiter until his death in 1978. Dick Denney, the man credited with kickstarting Britain’s guitar amplifier industry, remained active in the music scene, and was still involved in the production of Colorsound wah pedals for Macari’s (London’s famous music store/ rock star hangout) when GP last spoke with him in 1997. He passed away in 2001.

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