This might be old news to most people here, but I've just tried out some tubes in my amp, and of all the permutations the one tube that seems to make the most difference is the first pre-amp tube, the one receiving the signal of the guitar. In my case I tried out a few different tubes, but there is this one that really makes everything better! The overall tone of the amp, the signal to noise ratio, everything is just better with that one tube. I know that a tube amp is a system, and everything works together to create sound, from the input tube all the way to the output transformer, but talk about an inexpensive 'mod' that works! Anybody here has had a similar experience?