@mulveling and @mlsstl thanks for the info & advice. I will look into those Schitt SS 6SN7s. Currently I have the EHs that it came with in those slots. Thanks again. Stuff like this makes this site great.
Question about the headphone amplifier in tubed preamps
. . . specifically the Cary SLP-05, but I think the question would be applicable to any tubed preamp with a headphone amp built in. But my question is: I have all eight 6SN7 tubes installed, although I don't own headphones and probably won't in the foreseeable future. Since I never have the preamp switched to headphones, are those two 6SN7s only in a standby mode when I have the preamp turned on? And if not, should I remove those two tubes and cover their sockets with electrical tape & thus preserve those two tubes for use as "just-in-case-spares"?