Thanks for the fast reply!
I havn't thought about that. Ye, I know that the audio is a voltage of variable amplitude and frequencies. But I'm not so into the AC/DC part... We made a amplifier to the mic and it works good with amplitude. But do we need other amplifier to sample frequency?
This should be the same amplifier as we have at the moment: http://www.electrokit.com/mikrofonforstarkare.46099