60W 8Ω Power Amplifier Circuit Diagram

Description

This circuit was developed and produced during the '80s and has functioned reliably since that time. It doesn’t present any particular constructional challenges, beyond the important considerations concerning the provided power supply – selecting an appropriate heatsink and ensuring a good match between the driver transistors. Diodes D3 through D9 should be mounted above the output transistors on the heatsink to facilitate thermal coupling. The trimmer resistor R15 is employed to precisely regulate the output voltage of the amplifier, which occasionally exhibits intermittent operation before stabilizing thermally. With the trimmer TR1, the amplifier’s bias current is set between 50 and 100 mA. This bias current can be measured by observing the voltage drop across the high-value resistors R36 and R37, yielding a current of approximately 75 mA under typical operating conditions. The voltage values indicated in the schematic are original values, however, they may possess a tolerance of approximately ±10%.

Circuit diagram

Parts list