Hi all. I've just started playing around with my microcontroller. I built the electret pre-amp presented here: http://www.minidisc.org/mic_preamp/Simple Stereo Electret Mic Preamp.htm I would like to take the output and feed it into my sanguino. When I monitor the value being register on the analog pin (10 bit ADC) via serial comm, they mostly seem to float between 300 and 400. When I ground both circuits together the analog pin stops drifting, but if the mic single is coming through at all, it's barely more than one or two increments. Do I need more gain? Any general suggestions welcomed. Cheers, L.

 

Did you build it exactly how it is shown with a 9V battery? How are you powering your sanguino? If it is not being powered from the 9V battery, did you connect the grounds of the circuit with the sanguino together?

Also, the capacitor at the output of the tl072 will remove the DC component of the signal and bias the output around GND. Therefore, I think your signal will be able to go below ground when it reaches the sanguino, which is not good. The sanguino probably needs a signal between 0V and 5V for its ADC input so the final signal needs to be biased at around 2.5V.

Are you using the higher gain setting?