The Vox AC-30 Super Twin takes the sound and functionality of the classic AC-30/6 and splits it into separate head and speaker cabinet units to isolate the amp's electronics from the vibrations of the speakers. The closed-back or "pressurized" speaker cabinet also made it a bit more suitable for bass guitars than the standard combo model.

Some time in 1965, the cosmetics of this amp changed slightly from the original brown cloth/square head box to move toward the black diamond cloth, control panel-mounted Top Boost and a funky trapezoidal head cabinet that sat atop the new tubular chrome stand. The Super Twin was also available with optional Top Boost controls for the Brilliant channel, either with those knobs eventually moving onto the control panel itself. A version with reverb, which can be found here, was also available up until the demise of JMI in 1967/1968.