I've been in the market for 5F1 champ but I can get a really clean 5D2 right now; it's in excellent original condition and sounds great; It looks like most 5D2s were wide panel even in 1955 so this narrow panel 5D2 was likely a transitional amp? I suspect that this is actually a 5E2 and they were still using the 5D2 tube charts. How can I verify? In doing some research on the circuit, I found this quote at carlscustomamps.com and was hoping I could get some perspective from this board. What does he mean by flawed power section? "Wide Panel 5D2 1955 This was the first Princeton to use the 12AX7 rather than the 6SL7 or 6SC7 of previous models. Fender went back to a grid leak biased first gain stage giving the amp a gritty sound. This is rare one. Again the power section is flawed in these amps and uses a similar configuration as the octal models. Increasing the filtering and some other slight changes can great reduce hum and increase punch. Adding a 3 prong grounded cord is a necessity. I also recommend adding 2 watt 1K screen resistor and replacing filter caps over 10 years old for the best sound. I've also tried this circuit a but found I prefer the cathode bias of the 5F2A later tweeds in a 12AX7 pre-amp. Narrow Panel 5E2 and 5F2 1955-56 These rare versions were made with a cathode biased first gain stage. They also introduced negative feedback which gave them a smoother more even sound. Both used a choke transformer in the power section with rather minimal filtering. So additional filtering is helpful here to give amp punch and reduce hum. Adding a 3 prong grounded cord is a necessity. I also recommend adding 2 watt 1K screen resistor and replacing filter caps over 10 years old for the best sound." Has anyone actually seen a narrow panel 5D2? or were they likely 5E2? Thanks all!