How can I get rid of humming from AUX cable?

I have a realy long AUX cable that i use to connect my PC or my Ipod to my hi-fi system and i keep getting interference from it. I constantly hear a loud humming or rippig sound and sometimes i even hear people talking faintly:) Is there something that i could build for the cable that get’s rid of the interference. I still have a bunch of diodes and capacitors and stuff like that from a physics class if someone knows there way around that stuff. What could i do to fix this?