- similar to the AC-10 Twin, except in piggyback configuration with a separate head and 2-10 in. speaker cabinet, a seven-tube chassis, preamp: 1 X 12AX7/ECC83, 3 X 12AU7/ECC82, power: 2 X EL84, rectifier: EZ31, and reverb with a reverb control, mfg. 1963-65.