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.

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.