?OK to run 30 ft RCA from amp to preamp?

I am considering changing my set-up. Is it advisable to use 75 ohm, RG6 shielded cable with Canare DIY RCAs for a 30 ft run from preamp (BAT3i) to Primaluna 7 monos. Both are tube components. Speaker cables would be short, 2 meters. Are there any issues?

The system has developed "air" hiss/noise coming from the speakers. It is quite audible. I play mostly vinyl and I can hear it between tracks and between LPs. It seems to have increased over time. Could this be related to the interconnects I described above (although they are only 3 meters long)? Could it be tubes going bad?
Any help, advise is greatly appreciated as I am technically challenged.
I have a pair of Blue Jeans LC-1 cable running about 28 feet from my Aragon Stage One processor to Bel Canto M300 monoblocks, in and around AC, other components and other interconnects. No noise. My speaker cables are Speltz anti-cables running 3 feet to VR-4JRs. I suspect either the shielding is inadequate for the situation, or there is another source of noise.
RCA interconnects are suppose to be 50ohm, video and digital cables are 75ohm.

Try lifting the cables off the floor on paper cups, and even consider spraying some antistatic spray on the cables and floor especially if you are running your heater and have carpet.

Move the preamp close and try a short interconnect to see if the cable is the issue causing the hiss.. This might be painful but just get some cheap speaker cable (16gauge ratshack or something) so you only have to move the amp near the preamp.

If you are running a tube phono, swap those tubes out or swap them left-right if one side is doing it more than the other. This way you can check to see which tubes you are having issues.
I'm impressed by your results- no noise. To what do you most attribute your resiults to, the LC-1 cable, or the Speltz? Or just lucky synergy?
Could you describe the anticable?

I was not aware of the 50 ohm vs 75 ohm. Very well could be a problem.
BTW, are those biology books in your room?

Thanks for your help. Both good ideas to consider.
Oregon: it's actually an art book next to a bunch of music books.

Another side note I have lived in a number of apartments and now finally a house and had certain gear that was completely silent at one place and hissy at another place due to power issues. I have used regenerators (PS AUDIO), Balanced Power designs, dedicated circuits, and finally regrounded the house with two 6' grounding rods. So this could also be a power/ground issue. or a preamp/amp sensitivity mismatch (I had a problme matching CJ preamp to Lamm amps and caused hissing and buzzing..) I had to take some of these offending components over to a friends house to realize that my house was the problem.