RFI in tube system

I'd look into replacing preamp tubes.

Do you have any coax cables near your pre-amp? I had an ARC REF1 that would get noisy if I moved my tuners antenna coax to close to it. Sounded just like a tube getting noisy.

try using rfi chokes. i have a few i'm not using. i'll sell them to you for $1.00 each + shipping. they can be placed over interconnect cables, power cables and speaker cables. in your case, the preamp power cord and interconnect between pre amp and power amp might be a good start.

Try hooking up the pre and power amps normally, with the interconnect that would connect to the CDP in it's usual position(but w/o the CDP). Turn up the volume on the pre(Don't touch the interconnect) . Is the radio signal there? If it is: Turn the volume all the way down, remove the CDP interconnect and turn the volume up again. That should tell you if the most likely antenna in your system is the culprit(the CDP interconnect). Second would be the pre itself. Try some shorting RCA plugs, if that's the case. For instance those mentioned halfway through this article: (http://www.sixmoons.com/audioreviews/acousticrevive/ground.html) If you don't want to spend the $275 on those plugs, here are a couple other suggestions: (http://www.cardas.com/content.php?area=products&content_id=7&pagestring=Accessories&product_id=29) Music Direct, Needle Doctor, Audio Advisor and Galen Carol all sell those. Then there's the cheapest route:(http://www.siteswithstyle.com/VoltSecond/Shorting_plug_rca/shorting_plug.html)

Are any other components plugged into the preamp? Try removing them, so that only the component you are using is connected to the preamp at one time.