What "search phrase" did you use to find that - or was it your knowledge. I made some searching without finding anything useful....
I usually put the whole question into Google then start deleting parts,
But looking at my history I searched:
"Fujitsu Siemens Amilo Li1705 ubuntu" and got the headphone jack hit on the second entry- the Fujitsu forum, just lucky I guess.
Would try and help more but you always get there first