Don't mean to interrupt the flow of the conversation. I just replaced the tubes in my Primaluna preamp with tubes from Vintage Tube Services (Andy) of Rockford, MI. They are only in the unit for a couple of days now but the music is back in a very pleasing way. More clarity, dynamics, and substance. Highs are definitely more extended. I have to say that I was stopped in my tracks several times by the sound change. Big smiles and Oh my's! Brushes on the drum head hissing sound like brushes on the drum head. Andy was very kind, patient, and knowledgeable during our conversations. He recommended RCA 12AU7's. I purchased a matched set of four. Terrific and thanks to Andy!