The one on the left is for Europe (230V/50Hz)
The one on the right is for USA (120V/60Hz)
The 120ohm resistor should be 10W.
All caps should be rated at 450V
The PL500/PL504 parameters are:
Va - 275V (static) 550V (dynamic) 7kV (pulsed peak)
Ik - 250mA
That are the important parameters for designing the power supply. We only need the static voltage required. The dynamic voltage is when the anode is transformer coupled. So we set the Plate voltage at 275V and the cathode current at 250mA. I'm not even sure that these parameters are optimal, because the maximum power dissipation stated in the datasheet is around 22W, but at 275V/250mA the dissipation comes to around 70W. That's a very large discrepancy. Just stick to more normal tubes like EL84. I made an excellent 15W amplifier with 2 EL84 tubes in a push pull topology. I can upload the circuit i designed somewhere if you're interested.
