I'm thinking about a tube swap in my Mesa Walkabout, if that indeed will help with my percieved problem. My rig consist of Fender dlx Jazz > Walkabout > Epifani ul410-2. At lower volumes, the sound is perfect, but as things get turned up as the night progresses, the overall sound gets a little distorted. The Amp settings are basically flat, gain around 11:30, bass at 12:00 and mid at 12:30, treble around 11:00. I'm only using the master volume to go louder, not adding any eq or gain. A question for the Mesa experts... Would it be safe to assume that gain drives tube #1 and the master drives tube #2? Going on that assumption, could I change out tube #2 for something a little cleaner in sound? I've read the Walkabout mega thread but with over a 1000 replies, I got lost. Any opinions and suggestions for that tube would be appriciated if you think that would help.