I'm actually trying to digitize an audio signal. I have a sensor (Geophone) that produces a signal, is goes through a pre-amp, then to an LM386 amplifier. The output produces a mono audio signal. I'm trying to condition that signal such that it is suitable to put to an analog pin on the Arduino. I am thinking that it needs to be rectified, and limited so that it can't produce more than 5V. In the hyperlinked schematic, the lower right corner shows the Arduino interface, which in parallel with the speaker audio output. It uses a 5.1 V zener to limit the voltage seen at A0 on the Uno. I'm not sure that it is doing the job well enough though.http://www.flickr.com/photos/7697481@N04/8373568939/
Hopefully the link I attached shows the schematic. If someone might be able to suggest a more effective way to condition the signal for the Arduino, I would appreciate it.