I would like to ask, how someone can determine the voltage drop and the output voltage from a tube rectifier like ez81, 6201, 5U4, 5R4, 6AX5 and so on. Can the tube datasheet help me with that ? Is it a real life or simulation with a software test iterations? Is it being read from a chart or its a calculation formula? Or maybe its a ratio of the current being pulled from the rectifier that determine the rectifier voltage drop (sagging) ?