[linux-audio-user] recording guitar - level problems

Hi, I've setup a new FC4 system with alsa, jack, etc, and a SB Live card. I'm trying to play some guitar thru the line in (eventually into sooperlooper, maybe audor, etc). No matter what I've tried, if I try to get any significant volume, it's distorted terribly (not to mention some terrible humming - something else I have to look into yet...) Are there any simple guidelines for getting a nice clean guitar sound? Could any one point me in the right direction? or any good references out there? There's seems to be a lot of places to set the levels: guitar, amp, alsamixer (capture, line in), but I feel like I've tried it all. I'd like to go thru my amp first, which has a line out and headphone out. I'm also willing to invest in some new hardware if that's what it takes. thanks.