Understanding Bias Networks in Classic Germanium Audio Amplifiers

Summary: This video studies a 1966 transformer-coupled germanium power amplifier stage and identifies the key devices in its push-pull output section. It also calculates bias current, power dissipation, and the small 0.2-volt germanium base-emitter drop. Why This Matters: Bias conditions in germanium stages differ sharply from modern silicon designs. Understanding these differences helps engineers evaluate vintage equipment and avoid incorrect device substitutions. Content covered in the video: • Identifying TO-3 germanium output transistors in a 1960s Sylvania stereo amplifier. • Reviewing the transformer-coupled input and capacitor-coupled output arrangement. • Locating the 2.7-ohm and 390-ohm bias resistors on the physical chassis. • Redrawing the amplifier as a simplified push-pull output stage. • Calculating the bias-network resistance, current, and approximately 4.3 watts of dissipation. • Determining the 0.2-volt base-emitter drop associated with germanium devices. • Explaining why silicon replacements would produce severe crossover distortion in this circuit.