Circuit - Audio Signal Detector/Switch


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Last Updated on: 08/29/2008 02:09:06 PM

Audio Signal Detector/Switch Circuit
designed by David A. Johnson, P.E.

Click on Schematic below to view PDF version of this Circuit

For some audio systems it is desirable to have an automatic switch circuit turn on other devices, such as an amplifier, if an audio signal is detected on one line. The hobby circuit below will activate a transistor switch when it detects at least 50mv peak to peak of an audio signal. The switch could be used to turn on a relay, routing the signal to where it is needed. A single 3v lithium cell will power the electronic circuit for about 5 years.