I'm loving my Valve Sr. head. I run it through a 1980s Mesa/Boogie 1-12" cabinet and get a great bluesy sound. I upgraded the reverb tank to an Accutronics unit and that fixed the only thing I didn't like about it. I'm not an amp geek (er, enthusiast) but I wonder if there are things I can do to the amp to notch up its sound. Mind you, I love it now, so I don't want to radically change the sound. (My fear is that upgrading to new tubes would do that). But what are the other options available to me? Is biasing something to look at? What does that entail? Also, I read here and there about people modifying the capacitors or such? Thanks in advance for any advice you can offer!