I'm teeing up a few projects and wish to enjoy some local sales. The larger the order the better shipping rates. The first two projects are definitely a Harvard and a Champ and then maybe a Deluxe micro. I am very inexperienced at this (but totally hooked) having only built one 5f2a, so please bear with me. I will probably go with Hammond(s) as they can be sourced here, but I've included specs for a 40-18027, TP-25, and a Mojo760EX for comparison. Hammond 290AX; Hammond 290CAX; CT 40-18027: Allen TP-25 Mojo 760EX ma = 100 ... 115 ... 100 ... 150 ... 75 Volts = 650/550 ... 630/550 ... 630/550 ... 620 ... 330 Heater CT = yes ... no ... yes ... yes ... no Bias tap = no ... no ... no ... yes ... no Weight = 2lbs. 15oz. ... 4lbs. 1oz. ... 4.5lbs. ... 5.1oz ... 3.4 lbs. My first question is why the weight differential between them especially the AX and CAX? And indeed, what are we getting for the extra weight? Next, the 5f10 calls for 305v. but when I use the lower voltage I get 328v. with this formula (275 X 1.414 - 60v. ) and I get 343v. using this calculator...https://thesubjectmatter.com/calcptcurrent.html My wall shows 121 volts and I realize that can be an issue. How important is that 305v. target? If so, would a zener string be the route to go? The 5f1 doesn't pose an issue regarding B+ v. with the AX or CAX? Which Hammond tranny (they are the same price) would you all recommend for the 5f10 and which for the 5f1? It seems that the AX would suffice for both (and it has a heater CT) but I've read lots on here recommending the CAX specifically for the 5f10. The Micro calls for the 40-18027 and apparently it can also be used for the full blown 5E3. Would the AX work for the Micro seeing as how the milliamps are the same as the 40-18027? Thanks for any help and please straighten me out if I'm not thinking this correctly.