The output from the interstage transformer was then directed to four silicon 2N3055 NPN power transistors in a push-pull OTL (output transformerless) circuit. The output transistors were mounted to large stamped aluminum heat sinks to protect them from thermal overrun. Fortunately for those making repairs, replacement 2N2924, 2N3054 and 2N3055 transistors are relatively inexpensive and are still commonly available from electronic supply houses.
The DC power supply for the amplifier was also housed on the power amp chassis. The DC power supply utilized a power transformer with a 120 VAC primary and a secondary of approximately 40 VAC. A pair of aluminum and steel plates, bolted to the side of the amp chassis, stood between the transformer and preamp section of the amplifier. These grounded plates served to electronically shield the preamplifier from hum enducing fields emanating from the transformer.
A bridge of four discrete diodes provided rectification while a pair of 5000 uf 40 volt smoothing capacitors further cleaned up the AC ripple. The basic operating voltages coming from these filter caps were +31 VDC and -31 VDC. A nine conductor modular plug connected the power amp and preamp modules. This plug supplied DC voltage from the power supply to a ladder of voltage dropping resistors to provide appropriate DC voltages for the preamp section.