Hi 6SN7 lovers! Was hoping to get feedback from some experienced folks before giving up on some of these tubes.
I've been trying to acquire a collection of nicer vintage 6SN7 tubes for my Woo WA5-LE, and am stumped by some of the better-reviewed tubes sounding not-so-hot, and the most "common" tubes I have being among the best of the bunch.
From left to right (top row), we have (1) Sylvania "Bad Boys" (non-JAN) with matched date code, (2) more Sylvania "Bad Boys" (JAN) again with matched date code, (3) very non-exclusive Sylvanias I think from the 60's, but I don't actually know, and then (bottom) (4) Sylvania 6SN7Ws.
Pair (1) sounded very good (excellent clarity and presence), but one of the tubes, despite testing well, was very unstable (I could initially coax it to life with some tapping) and died on me about a week in. I didn't
really get to fully evaluate, but they sounded
much better than... Pair (2) despite looking (and supposedly testing) NOS, sound absolutely dull dull dull (poor detail, veiled, poor treble extension) - least favorite pair here. Pair (3) came with my amp, and despite being the "no big deal" tubes have the most clarity and airiness of the bunch and are my current favorite. Pair (4), which should theoretically be better than the black-base-yellow-label tubes are not as clean, a bit slower, and slightly tubby bass.
Most burning questions: Is it possible for one pair of "bad boy" tubes (2) to be
that much worse than another, theoretically better-testing pair (1)? I burned them (2) in for about 30 hours, but is it possible that they "open up" (would have to be a LOT) with even more burn in? I only have another 3-4 days in my return window.
Other than that, just wondering if anyone else has had similar experiences, or if I may be losing my mind. I don't mind paying fair market price for good vintage tubes, but at the same time, it really sucks to be disappointed when they go into the amp. I know tubes need to burn in, but some of these would need a pretty major transformation for me to be satisfied with them, and I just haven't had any other tubes change enough on me to have such an expectation.
Chain for reference: Custom NUC server w/ Roon ROCK --> Chord DAVE --> Woo WA5-LE --> Utopia
Thanks in advance for any thoughts!