I recently got a used 5e2 modified circuit amp. It is made to take a 6550 power tube, and has a beefier transformer to presumably achieve 20w. Don’t know if it does, but it is fairly loud. Swapped in a cannabis Rex for the stock Chinese speaker, and it sounds nice even before breaking in. I have been having crackling issues with it so I checked the tubes. The power tube is not a 6550 but a sovtek 6L6. The preamp tube is unlabeled and the socket is not well attached to the chassis, it’s loose. It has a 5AR4 “made in China” rectifier tube. I’m clearly going to have to sort out the tube socket. I figure I might as well swap out all the tubes as well. I have no reference to identify the preamp tube but it appears to be a 12a?7. I’ve asked the guy I got it from if he knows, as well as a dealer of the amp. I am contemplating leaving the 6L6, but the 6550 is the tube it’s made for. I’d like the added volume from the 6550, but the 6L6 is going to be closer to that “tweed” tone right? Last question, I understand what the rectifier tube does and am wondering which rev tubes are best? I’d like to get the amp running hot, and really pump some sound from it. Any opinions welcome fellas. Edit : since the ampnis based on a 5e2, and I don’t believe the preamp circuit has been modified, it would likely assume a preamp tube for a 5e2 would be correct?