Protective circuit for audio amplifier

摘要

Between the mains input terminal and the power source primary is incorporated a power relay with a switching coil. The power source has an ON/OFF switch. An audio signal voltage is amplified by a pre-amplifier. The audio signal from the latter is treated by a power amplifier, feeding a reproduction loudspeaker via output terminal. An interference detector acts on the power amplifier overcurrent and a DC voltage at an output signal line of the power amplifier. A control receives a detector output magnitude and controls the feed of current to the relay coil and thus the power relay ON and OFF switching. An auxiliary power source completes the structure, coacting with the control.