Marty on those jacks ya just need to turn down the volume as low as usable, (unless the soundcard is junk) Being I have many USB and pcmcia audio/video devices for laptops I can pre-arrange to pull audio from a client's notebook computer, or hopefully have them come to us and produce them on AVID and produce them to DVD. And will do it as a convience (free of charge) to us to save us the hassle of a trainwreck onsite. (it's a rare case)
It makes life a real nice world during someone's wedding.
P.S. Direct Boxes work real nice too Behringer makes one that actually is not junk. That goes to mic level, and pads the input levels.