hello,
thanks for all the answers.
for those who gave advice with main mixer, 'sorry I wasn't that clear. but mixer's input gain was max. and it was only half on the meter. then boosting mixer's channel/master only made my sound horribly distorted.
it seems that getting soundcard is a good option as I understand that clemen's explanation on headphone jack out problem. (btw, I never, ever saw a lap top computer with line out. does it really exist or you mean a desktop pc with some tweaks?)
this looks quite nice...as it's preamp AND soundcard...if soundcard doesn't make my signal louder, then I can use it as preamp..if I got it right.
http://www.thomann.de/pl/art_usb_dual_tube_pre.htm
does anyone used this with ubuntu 13.10 on modern laptops? a quick web search shows that it *can* work but have no drivers. 'seems that some people has troubles with it.