Yep, infinite sustain... My old Twin Reverb will make my Les Paul sing like that when I crank it, though I'll be the first to admit its 2x12 cab doesn't have the wall-shaking balls of a Marshall stack. Long ago I played for a while through a Marshall 100-watt head with a pair of 4x12s, and there simply is nothing in the world quite like that experience. Except maybe having a stage backline with 3 such stacks. I saw Blue Cheer at the old Electric Factory in Philly around 1968 -- that was the first time I experienced the power of multiple stacks. It was kinda like seeing God, you're never the same again.
I wanted a Twin Reverb and went shopping for one. I found a Super Twin that was in decent shape (electronically great but with the customary cosmetic wear n tear).
I started using it and was almost immediately disappointed - it was too loud! I had gone from a 65 watt single twelve Ampeg and a 60 watt single twelve Dean Markley and was used to achieving a certain amount of output concurrent with the saturation of tubes which gives that golden tone. What I wound was that most of the halls where I played couldn’t handle the Super at full volume. And anything less robbed me of the tone I sought.
Most of the Twins and Super Twins ran at 65 to 85 watts. There was a number of years where the Twin spec’d at 100 watts. I did some research and found that my monster was running at 135 watts. No wonder!
I never sold it but I did replace it. I wonder what the durn thing is worth now?