I had a couple of brand new Sovtek 12ax7lps tubes fail in my preamp after less than 9 months of use. So I googled "what would make sovtek 12ax7lps fail" and got this:
http://music-electronics-forum.com/t9514/
I don't know what design your preamp employs, but this may help explain. BTW, I have switched to NOS by RCA, Sylvania, Telefunken because I have been so disappointed by modern tubes. Also, you really should have your gear checked by a pro on a bench, you're just postponing the inevitable here.
http://music-electronics-forum.com/t9514/
I don't know what design your preamp employs, but this may help explain. BTW, I have switched to NOS by RCA, Sylvania, Telefunken because I have been so disappointed by modern tubes. Also, you really should have your gear checked by a pro on a bench, you're just postponing the inevitable here.