wow... after almost 20 years of playing, i get it. I am in the process of getting a Mesa 400+ and have been playing it for a couple of nights now. TUBE = BASS. i now understand "growl" and "bite", most importantly "warmth". any SS or tube preamp + SS will not equal what these do. unreal!!!! anyone else realize they were sloppy as heck after playing an all-tube rig for an extended (days) period of time? but, did i find it easy to adapt and USE it... dynamics take on a whole new meaning. just wanted to share!!!