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how to trigger a relay with audio signal (headphone)? Answered

Want output from headphone jack to power relay to turn on power amp

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Simple clap circuit to detect and amplify an audio signal enough to trigger a transistor latch that will trigger the relay. Google Clap Circuit and Transistor latch for schematics.

Excellent idea EXCEPT :
If I turn off audio, it will not turn off power amp............
I need continuous relay hold until audio goes to zero db.
Thanks for suggestion,
gramps

The use a transistor switch not a latching switch. The point is you want to take the voltage from the Clap circuit's output and use it to turn on a transistor that will activate the relay for you. When the clap looses audio the transistor looses power and the relay flips off again.