depending on how old the amp is, we added a ground loop breaker later, but where did you come up with this 62k value? We use 10 ohms in parallel with the .1uF cap (300VAC mains rated) in parallel with a 35A bridge rectifier
you can also try grounding one side of the filament supplies, which are AC
Surprisingly, we get only 10mVrms of "noise" on the output after careful selection of 12AX7/ECC83 tubes, which is going to have the most influence on your hum. Best I found were the JJ ECC83S which shipped with the amp. Old "special quiet tubes" may not be so quiet.