Bob B, your situation is why I only rock stock tubes after a similar experience. I’d rather listen to music than to be diagnosing equipment and/or switching out tubes. Good luck!
I love the Conn sylvania 12au7
I really like the Shuguang 12AU7-TG Nature Sound. It’s got an inner black coating. My pair is incredibly well matched and has a deep black background.
Psvane, which is comprised of former Shuguang engineers, has introduced a new 12AU7-S that’s supposedly better constructed than the 12AU7-II that ships with the BHK Pre. I have a pair of those coming in from Grant Fidelity.
At this point, I totally agree. I want to listen to music not fooling with tube noise.