I would like to be able to get a smooth cleaner overdrive out of the amp cranked without use of a pedal. It seems that it used sound like that when I first got it. I presume that new tubes will be helpful with the overall sound of the amp. But should I replace all tubes at once or only some of them. What types (brands and models) or tubes might be worth checking out? I have been told by a local repairman that he believes "hot" tubes may sound good but can create problems with the amp and that I might want to change all of the tubes at the same time. Suggestions? Thanks.