I recently acquired an older Sylvania 5U4 rectifier tube. I'm curious about giving it a spin in my AC30- '90s Korg-era RI, 6 input NMV with Blues. I'm aware of the voltage sag and decreased output I'd get from replacing the GZ34 with the 5U4. I don't know, specifically, if the PT in that era AC30 is up for the task though due to the greater heater current draw from the 5U4. Anyone?