Ski patrol in Chico? I haven't seen any ski slopes in Chico. But Tahoe, and Lassen are only a few hours away....
As for the ground loop isolator I got it at WalMart in Williams which is on I5 (It's the freeway that runs from one end of California to the other.) The alternator noise was driving me so crazy that I stopped on my trip and bought the thing. It plugs right into the RCA jacks between the sound card and the amp.
Ideally I should have fixed the ground loop but I got lazy since this thing solved it. Anyway, look for a ground loop isolator at WalMart that plugs in with the RCA jacks (not one that plugs into the 12v wiring). To be honest I have no clue why it worked by being plugged into the RCA jacks. Ordinarly I agree that alternator noise comes through the power source.
But, putting an isolator inline with the RCA jacks worked for me and I'm not going to complain.