Running an RCA interconnect of a length of 15-20 ft. should not pose a noise problem, provided it is well-shielded. However, your c-j tube preamp, like virtually any other tube preamp that does not use output transformers on the preamp outs, will almost certainly have difficulty driving an interconnect of that length due to impedance issues -- the bass will be rolled off. There is a lot of information available about the problem, which can be avoided with a solid-state preamp or tube preamp like those manufactured by VAC that use output transformers.
Building dedicated room with long RCA interconnect
I m current building a dedicated room 2channel?HT set up and is engaging Rives audio. To optimise my room set up, it is preferable to place my rack on the long side wall. Morever with a motorised screen and centre channel speaker, having equipment racks will certainly impede my centre channel set up. However, I m currently using CJ ACT 2.2 and CJ 350 amp which support rca interconnects only ( somehow CJ dont believe in the merit of balanced interconnect). I was told previously when I acquire about the lack of balanced interconnect connection that 5m rca interconnect would be fine if its properly shielded. Kindly advise as I have to decide whether to go with a design with equipment rack in between front speakers or at the side wall with long interconnect (15-20ft). TQ