W520 how to enable the mic (internal and external) in Ubuntu

My microphone was not working out of the box on my lenovo w520 laptop.

I looked al over the internet for solutions. Adding stuff to alsa-base.conf appeared to have worked for some people but never worked for me.

However, this solution worked for me :

type  :  wget -O run.py http://www.alsa-project.org/hda-analyzer.py
run : sudo python run.py , a window should open
Go to Node[0x14] AUD_IN
open a sound recorder session then press record.
Then play with the mute checkboxes while talking. For me it was the 5th one that worked.

Hope it helps.