The workings of this amplifier timer circuit is simple, when there is no input signal for 15 minutes, then the power or other devices connected to the switch relay will off.
When the P1 switch is pressed, then the power supply will flow into circuit including to any device that has been connected to the outlet SK1. The input signal received will be strengthened by IC2A and IC2B. LED diodes will ON when no input signal.
IC3 will set the timing for 15 minutes. The chain of C5 and R9 serves as a IC3 counter reset at the beginning power-ON. The switch P2 serves to disable the device manually.
Amplifier Timer: Auto off Timer Circuit Notes:
Pair this amplifier timer circuit only in the left or right of the line out channel on the amplifier. The way you can put two RCA connectors in parallel, or using signals from both stereo channels. The time delay of this circuit can be modified by changing the value of R13 and / or C6.