Best Tube to eliminate RFI

While not the world's most technically adept guy, I can't see how any tubes could be causing your problem; they're only amplifying a signal, and this isn't microphonics from your description. Bob bundus' suggestions are a good place to start; perhaps switching speaker cable leads could tell you if perhaps one of them is acting as an antenna? I had an Audio Matiere amp in my home for audition once and had a similar problem I couldn't solve with line conditioners, Versa Woodblocks, ferrites or the like; one friend of mine thought it could be a grounding problem within the amp, but since it wasn't mine I didn't follow up on that one. You might ask your Jolida dealer about that, though. Good luck!

Interesting, Albert, as I've never had a tube pick up RF--glad I saw your post, guess I've been lucky. Keithcady, do you have separate small signal tubes for each channel, perhaps if not in the preamp section maybe the amplifier section (I'm not familiar with the Jolida's circuit)? If so, switching them could probably tell you if the tube is causing the problem.