Thanks Wolf except MY experience has not been as good, at least the last two times out. I sure hope the third time is the charm. This time I purchased the one year warranty for an additional 20% of the tube price. The last two pair didn't last beyond 3 months, 6SN7 in a pre output stage. Maybe an unusual experience, or something wrong with my preamp, for sure not the latter, the problem is tube quality.
I test ALL tubes I purchase prior to installation and keep a log of the dates installed. In the case of the first two sets, when I noticed noise I checked them out and the transconductance had gone South considerably, not a short, the tubes just didn't hold up, one was marginal the other tested weak and replace. The manufacturer sent me another pair. These lasted a bit longer, 5 months but certainly no more than 1500-1800 hours and I'm being generous. When I installed the most recent tubes a few days ago I tested the old stock Sylvanias I had in the pre-amp that were installed a little over a year ago to replace the failed tubes. They tested stronger than than the new tubes I just purchased and the same as the day I installed them. Unfortunately these very nice Sylvanias don't come close to the sound of the Chinese tubes, it ain't a subtle difference for sure. For 250.00 is it unreasonable to expect at least 4K hours of life or more? Or is this the new normal or is my experience unusual?
