speaker hiss with audio aero capitole mkII

I have noticed a hiss from my egglestonworks andraII speakers that is noticeable from the listening position at the highest volume settings on the audio aero capitole mkII. The hissing comes from both the tweeter and the twin mid-range drivers from both speakers and is equal from both sp's. It gradually increases as the volume is turned up and is not present with the capitole turned off and the Krell fpb 300cx on. I have dedicated circuits with their own main panel and the capitole is connected to a PS audio P-300. The hiss is present also when the capitole is not connected to the P-300. I suspect that this relates to intrinsic noise or distortion in the capitole, possibly from the tubed analog output. Although the system sounds terrific, i am concerned that the hissing may be masking low level detail at moderate to high listening volumes. Has anybody had a similar experience with the capitole? Can this be improved? Any suggestions? Thanks.

It is clearly from the Capitole. I connected my other player (Rega Jupiter+IO DAC) and it is dead quiet. I even turned the volume down on the Capitole to -7db to match it with the Rega's 2v output and the hiss persisted.
One more suggestion. Try reversing the connections at the Capitole. See if the hiss follows. Also, do you have XLR connections? Trying a different output (XLR) might tell you if this problem is just in the terminal, or a least somewhere past the DAC. When you have tried all of the above, call Globe Audio. They are very helpful. I don't have globe's phone number handy; it is an '800' number. You can find it by doing a search for 'Globe Audio'.

I do suggest all possible tests before calling. The more you can tell them, the better the help.

Good Luck!
How old is the player? There are two 6021w subminiature tubes inside. If the player is more than about 18 months to two years old, those tubes may need replacing. They would not grow old at the same time (if you know what I mean) or in the exact same way, so you'd start to hear a little noise in one channel, then the other a little later....?
Interesting thought. Perhaps reversing the tubes will answer the question. Also, it could be possible--although a remote one--that one of the tubes just needs to be tightened.