The Vox Foundation Bass Solid State Amp - 1967 - 1972

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British Line

Solid State Foundation Bass Head
JMI Vox introduced three new solid state bass heads in 1967, the 30 watt RMS Dynamic Bass, the 50 watt RMS Foundation Bass and the 100 watt RMS Super Foundation Bass. All three shared the same two channel solid state modular preamp section and Thomas Organ inspired control panels. The Dynamic Bass utilized the 30 watt modular solid state power amp section from its guitar amp counterpart, the Conqureror. The Foundation Bass shared the 50 watt power amplifier section with the Defiant. The Super Foundation Bass and Supreme guitar amps were powered by the same 100 watt solid state power amplifier module.

The head cabinet for JMI and VSEL (1967-1970) Foundation Bass amps featured black Vox diamond grill panels on the both front and rear faces. The amps also included front and rear horizontal "Thomas" style Vox logos, two-pin corners, a Vox strap handle, traditional basket weave vinyl covering and gold string accents. The earliest of these amps would have a Jennings (JMI) serial number plate on the rear panel. The preamp circuit was detailed on JMI Vox schematic OS/137, the power amp circuit on OS/134. These schematics are available for purchase at North Coast Music.

A second version of the Foundation Bass head was produced during the Corinthian and Stolec Vox periods (1970 - 1972). While the front panel remained unchanged from the earlier model, the rear panel was covered in vinyl. Silver string replaced the gold string accents used on earlier models A crude silk screened serial plate was screwed to the back panel. These later solid state Foundation Bass heads utilized a revised fuzz and MRB circuit, detailed on VSL schematic OS/185.

The upper control panel of the Foundation Bass "Normal" channel included two input jacks, a Mid Boost switch plus volume, treble and bass controls. The lower control panel included a distortion or "fuzz" control and a three position rotary switch to select one of three mid range boost frequencies (450hz, 600hz and 750hz).

The distortion circuit included three germanium transistors. The fuzz was actuated by an external single button egg shaped foot switch.

The "Bass" channel of the Foundation Bass included two input jacks, a volume control and the Thomas Organ/Vox inspired "Tone X" control. There were no additional effects in the Bass channel.

Tone-X was a single tone control that replaced the normal bass and treble controls. Tone-X was a sweepable parametric EQ control that offered about a 6 db boost from approximately 50 hz (control counter clockwise) to 300 hz (control clockwise). While uniquely designed, most bass guitarists opted for the greater tonal variation offered by the traditional tone controls of the Normal channel.

Foundation Bass Speaker Enclosure
At just 26" tall, 22" wide and 15.5" deep, the original 1963 Vox Foundation Bass enclosure was barely large enough to house an 18" speaker.

The redesigned 1967 1x18" Foundation Bass enclosure was a bit larger than its predecessor. The new enclosure was two inches wider to match the width of the new solid state Foundation Bass head. The new enclosure was also 1" taller and 1.5" deeper than the original. The larger cabinet, combined with a tuned bass reflex port, improved bass response.

Foundation Bass "Roll-Away" Stand
Vox developed a two-piece "roll-away" stand for their solid state Dynamic Bass, Foundation Bass and Super Foundation Bass amplifiers. The stand was included in the price of the amplifier except for the 1970 model year when it was an extra cost option.

The lower portion of the roll-away stand was a chrome plated tubular subframe that bolted to the bottom of the speaker cabinet. Two 4" casters were mounted to the rear of the subframe. Two vertical tubes extended to the floor from the front horizontal cross member, leveling the enclosure to the casters.

The upper portion of the roll-away stand had a chrome plated tubular frame that bolted to the front top edge and rear of the speaker cabinet (see photo at left). The amplifier head was secured to this frame with two wingbolts. When the head was removed for transport, the upper roll-away frame became a hand hold, allowing the cabinet to be tilted back on to the casters and rolled like a dolly.


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Photos and editorial content courtesy Gary Hahlbeck, North Coast Music

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