The high frequency whine that you mentioned rings true to me. I had the same experience and found the problem to be with the tubes, not the preamp. Not sure what tubes you are using but I have had great luck with Cryoset. They cryogenically treat all of their tubes which, in my experience, has resulted in very quiet tubes that seem to last forever. I buy new production Gold Lions and they have been great.
Good luck!
Good luck!