A stereophonic transistor preamplifier

Designed to drive two transistor-power amplifiers previously described, this preamplifier contains all the controls necessary for stereophonic and monophonic programs. The first two of the three stages form a complementary circuit readily adaptable for the various input sources, which provides the necessary gain and equalization for low-level phonograph and tape inputs, guard voltages to reduce the capacitive effects of the input cables, and impedance transformation for high-level inputs from tuners and other tube circuitry. Loudness control is achieved by the combined effect of variable negative feedback and a novel tone-control arrangement. The frequency range, including the power amplifiers, extends from below 6 cycles to above 50 kilocycles per second.