Howdy guys- I've got a 73 Lead & Bass 20 that sounds great. Brought it to rehearsal the other day and it smoked. I had it dimed, but our drummer hits kinda hard. I just scored some 7189 tubes (they are in the same family as EL 84's) and wanted to know if it was safe to put them in the LB 20... I'm pretty sure I can put them in there as the Plate voltage on the LD 20 is pretty high... Just to make sure, is it OK? Also, generally speaking, what will the 7189 do to the sound besides make it a bit louder? Are there any guidelines for situations where I SHOULD NOT use a 7189 instead of a EL84? Any feedback (no pun intended) would be great.