I know plenty of guys who would mod in a bias pot on Mesa's. They didn't want to use Mesa's valves and had their own preferences.
You don't
have to use Mesa tubes, if you like 'em, fine. If not, you are free to get anything else you want, so long as it falls within the tolerances of the preset bias. Most tubes will work with a Mesa, the only ones that won't are the cheap shit, stuff that isn't matched, etc. Mesa owners often like tubes from Svetlana, SED =C=, NOS Sylvania (the elusive STR415), and Ruby's (Most Mesa branded tubes are from Ruby). I've heard that Groove tubes are at the bottom of the heap. My Mesa has TAD's in it, FWIW, and it hasn't exploded, or anything.
But be wary when choosing tubes. Remember that it will void your warranty if you don't buy Mesa tubes. Of course, if they don't find out that you don't, what they don't know won't hurt 'em.
