I seen something a while back were the cat 5 was tested against regualer sheilded rca using a neon light, the digital screen showed alot more interferance with th cat 5, also the resistance of the2 are not even close. head unit preouts are matched for the different resistance of the - and + in the rca. were as the resistance of the - and + of cat 5 would be even not making it a perfect match, although most people cant tell any audible difference between the 2 unless they have a lot of interferance indtroduced around the system. But that is just what I read.