I was hoping I might prevail upon some of the amp guru types in these parts.... I have a 1965 Fender Tremolux Amp that I recently acquired and noticed that it currently has a 5U4GB (a Sovtek) in it. From what I understand, the amp should have a 5AR4. I'm told that the 5U4GB draws significantly more filament current than a 5AR4 and some would caution that this could be hard on the PT. I believe there are other options for NOS rectifiers that would have a filament current draw similar to a 5AR4, but that would be significantly less expensive. I'm not a complete and total cheapskate, but I can't help but notice that a NOS 5R4 or 5V4 is significantly less expensive than a NOS 5AR4. From what I understand, the 5U4GB that is currently in the amp would have significantly more sag than a 5AR4 and I would need to rebias if I were to switch rectifiers. The amp sounds great now, but I don't want to endanger the PT with using an incorrect rectifier. Considering the 5V4 or 5R4, which would be the more appropriate and healthy choice for the amp in place of a 5AR4? Or would either be an okay alternative? Is there potentially an advantage of using one over the other when considering tone? Thanks for your help!