I have an alpine 9851 cd deck added an aux input for my ipod using an ainet-rca adapter and a monster rca-headphone cable. I can't tell a differtence when music is playing, but when I have no device connected and i have the deck on aux and the volume on, i can hear interference from the headlights, alternator? etc. Is this harmful at all or am i just being paranoid. Is there anything i could shield any of the adapters I have to eliminate this?
Thanks

Also, what size tweeters will fit the stock tweeter mounts in a 96 civic ex?

 

Just check on where the input cable is routed because it can pick up interference from just about anything in close proximity. I can get really terrible interference from my radar detector if its cables cross the aux input wires. You want to keep it as isolated as possible. I suppose you could shield it with something like aluminum flashing tape or a similar metallic material if need be. I wouldn't do that without then wrapping it with an insulator like electrical tape or heat-shrink tubing to make sure that it doesn't cause a short with something else.