The circuit protection output of power amplifiers and loudspeakers, dispose certain interesting elements, as the isolation of loudspeakers from the exit of amplifier, when is presented continuous voltage in his exit or when the temperature of heatsink, goes up excessively, providing simultaneously and time delay in the connection loudspeakers in the amplifier, so that we avoid pass in them, the known annoying noises from the charge - discharge of capacitors of supply.
It�s constituted by a binary comparator [ IC1 ], the transistors Q1-2 and indicative LED D5-6. The supply of circuit can become from positive voltage [ Point A ] of mainly power supply, which is stabilized by the D3 and the R17, in + 15V. Point B is connected in one of the secondary AC coil of main transformer. If close the main switch of main line AC, then a AC voltage (in secondary coil of transformer), is presented in the point B, it�s rectified from the D2 and it supply with negative voltage, via the R9, the Q3, this cut off and it begin charge the C4 via the R10-11.