This is a quote from zed audio "Interconnect cables are the first cables which the signal passes through from signal sources to preamplifier (in the home stereo) and from head unit to processor or amplifier (in the car stereo). We shall only discuss cables with RCA plugs at each end as they are by far the predominant cable type in this category. As in any interconnection, there are THREE main issues to consider. First the source's output impedance, secondly the cable's electrical impedance and lastly the receiving gear's electrical input impedance." which can be found at http://zedaudiocorp.com/index.php/tech-talk/cables.html The quote below, can be found at BCAE1 " RCA Cable Construction The RCA cable, which is used in virtually all car audio installations, is a specialized cable which is designed to transmit audio while preventing noise from entering the audio stream. As you can see in the diagram below, the center conductor is "shielded" from noise by completely enveloping it in a braided copper shield conductor. The shield is connected to the reference terminal of the audio source. You remember that every measurement has to have a reference. The same is true when you are sending a signal (audio in this case). This is so because the next device in line must "measure" the level of the incoming signal. If it does not have a good reference, the signal quality will suffer. I will explain "audio grounds" in a section to come."Under section 61 I highly recommend you visit both of these sites to grasp a better understanding.