I apologize for the noobiness. I just bought a new BJ NOS. All stock and I haven't done any mods (I don't know how and what). I also have 1 unused new production Tung Sol 12ax7 lying around here. Can i swap this with one of the groove tubes of the bj or does an amp always have to have the same kind of preamp tubes? If i can swap it, which one where i can have a higher headroom? Thanks in advance.