Ok so I'm looking to add a microphone to an existing project that has a number of LED light sections and then write some code to use the mic as an analog input. Basically I want to add a music interface function to my set-up, a simple sound sensor mode and then a VU meter mode. I currently have 16 LED sections I'm able to control via a couple 74HC595s. I was looking at LM3916 bar graph drivers when I thought I could do the same thing with just some lines of code in the ATmega along with the microphone. But it seems I need an amplifier and to the best of my findings I have come down with two main choices. The first one being transistor based basically http://tinkerlog.com/2007/05/20/cheap-sound-sensor-for-avr/. And the second one adding in a LM386 chip http://tinkerlog.com/2007/10/22/diy-tengu-on-a-breadboard/. It's going to be mounted on a motorcycle so not right next to a speaker, it would sense music from a car or radio. Would this requirement lead to uses the second option? Which is better overall? I'm guessing the one with the LM386? Has anyone used such a set-up successfully?
What kind of mic are you using? Electret? Piezo? Dynamic?
I'd go with a JFET input opamp like the TL072, though honestly a 741 would probably be fine too for just sensing. The LM386 is a power amplifier so its designed to drive current through a low Z source like a speaker.
You need a voltage boost, from the low voltage (~10mV) from a microphone to something scaled for the Arduino's ADC (~1-5V). Look at this http://www.play-hookey.com/analog/non-inverting_amplifier.html
I'm not too familiar with audio components so I have a electret condensor omidirectional MIC. Thanks for your reply, I did jump the gun a little bit and ordered the parts for a LM386 set-up before you responded. We'll have to see how effective I can get it to work by tinkering with it...if it turns out poorly then I'll just have to explore the TL072 route as you suggest. In the video of the Tengue Clone the guy was using a LM386 set-up that I'm basically going to try the same. May not be the best route but then being anxious to start and not knowing how audio really works certainly didn't help me any!
The 386 will probably work just fine.