I have a Panasonic head unit that among other things, has an aux input for whatever I may please. I have a jvc sirius satellite unit, and when I use it I get engine whine. I thought it was power related, but I tried my portable battery powered mp3 player and I get noise through it also (not as bad, but still audible). I had run a cheap rca to 1/8 jack behind the dash for custom mount, but pulled it to get it away from all interference, and still get the noise. Would a shielded cable be necessary for this use?