Sound triggered switch from a low audio input.

What i want to do is detect when an audio signal is present .

eg . sound from a mic or guitar (low level input)

My method is ....

(MIC) > (PREAMP CIRCUIT / OPAMP) > (SINGLE STAGE RECTIFICATION) > (ARDUINO ANALOGUE IN )

and my code would just say :

if ANALOGUE IN is > a ref voltage then do events ect.

Any ideas or better suggestion?

and if my method is good some suggestions on a good amplication stage would be good .

cheers

luke

I would put a capacitor on the output of the rectifier and a resistor across that to act as a peak detector.
Any op amp will do for your amplifier. I would AC couple it as well.