I got a set of NOS 6V6 Brimars from Mike over at http://kcanostubes.com and put them in my /13 FTR37 today. I really wondered about this, because I had a set of what seemed to be perfectly good Tung-sol reissues in it, but...wow. I had no idea what a difference those Brimars would make. But yeah, I put them in, biased it, and used it at practice with my band for about 3 hours. Just amazing. I won't bore you with hyperbole here. If you're wondering "do they make a difference?", the answer is yes, yes they do, and its wonderful. They're kinda spendy, but until someone can make new tubes that make your amp sound like these do, they're in a class by themselves, I think. Just had to share. Carry on.