Abstract: A speaker protection circuit comprises a detection circuit connected to the output of a power amplifier circuit and detecting overvoltage exceeding a predetermined level developing at the output, and a first relay circuit to disconnect a loudspeaker from the output of the power amplifier circuit when the detection circuit detects the overvoltage, the speaker protection circuit further comprising a second relay circuit which causes a power supply circuit connected with the power amplifier circuit to drop or cut off the supply voltage to the power amplifier circuit when the overvoltage develops at the output of the power amplifier circuit. The second relay circuit has normally closed contacts connected between a secondary winding of a power transformer of the power supply circuit and a rectifier circuit. In order to drop the supply voltage to the power amplifier circuit, a resistor is connected in parallel with the normally closed contacts.