Hey I have just spent the past 4 hours to try and get the microphone working with ALSA however I have had no luck, I have tried different model configs for modprobe. Here are my details

Laptop: Asus C90S
Distrubution: Archlinux
ALSA version: 1.0.20-1
Kernel version: 2.6.30.1-1
Dmesg: http://pastebin.com/m31f9f94f
Amixer: http://pastebin.com/m698673d
Aadebug: http://pastebin.com/m2173ac90
50-Sound.conf (in /etc/modprobe.d/): http://pastebin.com/m1137bf73
modprobe.conf (in /etc/modprobe.d/):
http://pastebin.com/m1fcbe703

Any help would be greatly appreciated

The only solution to make microphone work is to install linux-backports-modules-alsa-generic...

Just go to:

Menu / System / Administration / Synaptic Package Manager

And search and mark for installation:

linux-backports-modules-alsa-generic

tip: if you have multiple versions click on the first and read the description which should inform what name to install...

If after the reboot and mic mute is off, still does not work, just go to terminal and type:

sudo nano /etc/modprobe.d/alsa-base.conf

and add or change the following:

options snd-hda-intel model=auto enable=yes

Then Ctrl+X, type Y to write and exit, reboot and mic will work.

Bye and have lots of fun with Ubuntu (the best).