carlos, i saw your post and wondered how you would compare the following 12au7 tubes which would be used in the pre amp section of my amp. the 3 tubes are: 1.tungsol 2. amperex holland 3.mullard. any thoughts comparing these for use in a unison research sr-1 amp would be most appreciated.how do they each sound and how would you recommend them? are they alot better than my stock phippis jan 1980's tubes? thanks so much. stephen
