Coe, I asked the questions that I did to establish in a simple way that 1) the noise was not in the mono's which was easily eliminated by either turn off or a mute switch and 2) that the noise did not originate in a source, such as a tubed cdp or a phono stage, which would have been revealed by simply changing the source using the selector switch and any noise from your source would have increased when you rotated the VC.
Now you have reduced your potential problem source to the obvious 1) tube noise caused by failing tubes, ot the not so obvious 2) a defective internal component in the pre-amp which has failed (or is failing).
Problem source 1) is logical, except that noise from a pre-amp line stage usually is constant and not affected much, if at all, by using the volume control which typically only attenuates the signal level from the sources. Since use of the volume control does cause the noise to be amplified it suggests to me anyway that the source of the noise preceeds the line stage tubes (I'm not familar with the Cary pre-amp's design so that my be a meaningless observation).
Whether the tubes are a problem or not is made unlikely because you are getting the noise in both channels and it is unlikely that they all go bad at the same time. Possible, but highly unlikely.
All of this, except for one other consideration, suggets to me that your problem arises out of a defective component in the preamp which serves both channels and will need repair by Cary or, perhaps, a local techie.
The consideration that changes the entire equasion is your actual level of attentiveness to a slow and gradual degredation of your tubes in your last set up (for what ever reasons, you may not have been paying close attention) and in re-establishing you are paying close attention and notice the changes.
Regarding a solution, you are doing the right thing, getting a new set of tubes. You need to have a spare pair or two about anyway so if that is not the solution you have not really lost anything. If the new tubes solve the problem your done and will have a smile on your face. If not you're going to have to box it up and send it for repairs. At least thats what I would do, and I would most likely us Cary.
Hope that helps a bit. Good luck.
