electret mic input preamp

ok so ive been trying for about 3 days to get an electret mic to act as in input to detect sound etc, i give up

ive built a 1/2 watt amp and mic preamp etc nothing seems to work

i want to just buy something that i can connect straight to arduino analog input and an electret mic, or any mic.

would any of these work

http://www.maplin.co.uk/Module.aspx?ModuleNo=37746

http://www.maplin.co.uk/Module.aspx?ModuleNo=220052

http://www.maplin.co.uk/Module.aspx?ModuleNo=2921

thanks

What mic are you trying to use?

When you say:-

nothing seems to work

What were you expecting and what did you find?

You usually need at least a capacitor in front of the arduino and perhaps a bias circuit. See the input arrangement on this link:- http://interface.khm.de/index.php/labor/experimente/arduino-realtime-audio-processing/

i am trying to use an electret mic,

i was expectiong a value around 512 that would increase depending on the volume of sound, instead i got a value of 900 that would erratically change when there was sound

instead i got a value of 900 that would erratically change when there was sound

Yep that is what you should get.

You are sampling the waveform not the envelope of the sound so it will change like this. To get the envelope you have to apply a peak detector filter either in hardware or software.
The 900 in place of the 512 was due to DC shift on the output. You can correct this by AC coupling and biasing the input mid way with a potential divider with equal resistors like in the link I posted.