Visit North Coast Music...|..

Contact...

Tom Jennings, president and founder of JMI (the parent company of Vox) was keenly aware of the impact that celebrity endorsees would have on the sales of Vox amplifiers. Jennings scored a major victory in 1959 when the UK instrumental band the "Shadows"

replaced their Selmer amplifiers with the first generation Vox AC-15. In addition to producing instrumental guitar hits such as "Apache" and "FBI," the Shadows were also the backup band for the UK singing sensation Cliff Richards. The Shadows introduced many young British musicians, including the Beatles, to Vox amplifiers.

Can You Make It Louder?
In a televison documentary about Vox produced by the BBC entitled, "Vox Pop: How Dartford Powered the British Beat Boom," Shadows member Bruce Welch recalled a 1960 conversation with Vox chief engineer Dick Denney. Welch asked Denney if there was any way to boost the output of the AC-15. The sound of a fifteen watt AC-15 was easily overcome by an auditorium of screaming girls. At times, the Shadows couldn't hear their own guitars.

EF86 Preamp Tubes While most guitar amplifier manufacturers were incorporating dual triode tubes such as the 12AX7, 12AT7 or 12AU7 into their preamp circuits, Dick Denney decided to include a pentode tube, the EF86. Denney so preferred the additional gain and rich harmonics offered by the EF86 that he designed it into the preamp circuits of the Vox AC-2, AC-4, AC-6 and the Normal channel of the AC-10 and AC-15 amplifiers. As the AC-30/4 and AC-15 shared the same preamp circuitry, the AC-30/4 also utilized an EF86 tube in the Normal channel. Shortly after the AC30/4 amp was introduced, an unforeseen engineering problem arose. The EF86 tube used in the AC-30/4 preamp circuit proved to be susceptible to damage from excessive vibration. At the lower output levels of an AC-4, AC-10 or AC-15 amplifier, this was not a large issue. In the AC-30/4, the strong vibrations caused by a 30 watt power amp powering two 12" speakers was often more than the EF86 could tolerate. As the EF86 started to break down, it often would became microphonic. Howling and ringing tones from the failing EF86 tube would at times accompany the sound of the guitar playing through the amp.

EF86 Tube

Control Panel, Jacks and Controls
The AC30/4 featured a black and gold anodized control panel divided into five boxes. The box at the far left was labeled "Inputs." The amp had four inputs. two each for the Vibrato and Normal channels. The input jacks for the Vibrato channel had white nuts, the Normal channel input jacks were black.

Moving to the right, the next control panel box enclosed the Vib/Trem controls. A three position "Speed" control adjusted the speed of the Vib/Trem. A second panel mounted rotary switch labeled "Switch" toggled between the tremolo and vibrato effects. An egg shaped foot switch turned off the Vib/Trem circuit.

The volume controls were in the control panel box labeled "Volume."

Next came the "Tone" control section. The "Brilliant" rotary switch affected the treble response of the Nornal channel. The "Bass" control rolled off the treble response of both channels.

The power switch, power indicator lamp, fuse and a mains voltage selector were on the right side of the control panel.

Cabinet Design
The AC30/4 was the first AC-30 to incorporate the traditional "split front panel" design shown at left. However, the early AC30/4 amps delivered to the Shadows still had a "TV" front cabinet.

Speakers While the AC30/4 shown at left had a pair of Celestion G12 Alnico "Blue" speakers, some early AC30/4 amplifiers were fitted with an earlier version of the same speaker, shown at right. These were painted tan and did not include the pressed steel magnet cover found on later Celestion Alnico 12" speakers.