I just had an interesting modded amp across my bench for a while. It's a blackface Fender Bassman, 1965 by the serial number, and it had some simple mods done that made it a real screamer, but it could have been reverted to dead stock condition in 15 minutes if you wanted to. The drawback is that it was SO hot that you sacrificed almost all of the clean headroom. As I investigated it, to find out what the mods were and how they worked, I soon found a single resistor change that was responsible for most of its impressive level of drive. The 470K attenuator resistor on the grid of the second preamp tube had been dropped to just 22K. Marshalls share that feature. There's a 470K attenuator between V1B and V1A on a 2203/2204 and other models that share the preamp/master volume circuit, and two resistors of the same value that serve the same function in a 1987/1959. Have any of you played with reducing these resistor values for easy gain boosts? What were your results and conclusions? I realize that if you go too low, blocking distortion is likely to occur. Of course it's easy enough to do this mod. But I want to hear your opinions before I even bother to try it.