Altough previous schemas give a current with non zero mean value, it is far from beeing continuous! Used as is for feeding an amplifier, an horrible hum will appear. Some kind of smoothing must now be done, which is in fact a low pass filtering with frequency cut off below fundamental frequency of rectified current. The most basic way of doing that is simply by adding a capacitor in parallel with the load :
This is the first basic schema, the capacitor loading. Very good as a filter, this topology suffers two drawbacks : first, mean value of voltage is widely loading dependent (``capacitor effect'') and second, charge currrent at start up can destroy the rectifying element (for high-vacuum valves, a maximum value for the capacitor is always given in data sheets). For avoiding those troubles, an inductive loading can be used instead, which smoothes current instead of voltage :
However, inductive loading is almost used only for gaz filled diodes or class B amplifier (because wide current variations will cause too high voltage variations in capacitive loading).