From time to time I hear customers complaining they can't get the sound they want and they look at their preset and all the tone knobs are at noon or only slightly deviated from noon. I ask why and they say something like "well, I don't want to stray too far from the defaults". Amps have controls for a reason. Don't be afraid to get radical with them, especially older amps. Those old amps were crude and not intended to deliver the more modern type tones players today want. For example, if I were to use a Fender model for a lead tone I would turn the bass way down and midrange way up as they get too flubby otherwise. As an excellent illustration consider Joe Bonamassa's settings: Bass is all the way down, midrange is almost all the way up. Pretty much how I would dial in that amp (59 Twin or 58 Bassman which are very similar topologies). As you turn the volume up on these old amps the distortion is coming from the power amp and you need to boost the mids and cut the bass to flatten the response since the power amp's response follows the speaker impedance which is scooped in the mids. Otherwise the bass clips before the mids which causes flubbiness. That's also similar to how I dial in a Plexi. I crank the mids and lower the bass.