Any way to reduce pre-amp noise floor?

I have had my CJ ET3-SE tubed pre-amp for about a year now. When my system (McCormack DNA 500 amp, Esoteric X-05 CD, Aerial 10T speakers) is on and the CJ is set to "0" volume there is dead silence. However once I move the volume to to any level above zero ( no music playing, of course!) I hear a very soft but audible white noise. When I return the volume to zero the noise vanishes. This concerns me because I suspect that once the music begins to play, this noise floor becomes part of the overall sound.

This is my first "separates" system so I'm not sure if this is just a standard preamp phenomanon or if it is perhaps a sonic signature of CJ or if there is some real issue that needs to be fixed or can be tweaked. Any comments/suggestions will be greatly appreciated.