P-Series Valves, what to do with them?

[Terry]

I've always been uncertain what the 300mA means as regards a P type valve - 300mA max? And how the Dickens would you regulate a series chain? A bit higher mains and current goes up no?

Andy, as you say, if the mains voltage goes up, so does the current but only by the same percentage as a 6.3V transformer fed valve.

Is the 300mA figure a maximum figure? Is 6.3v for an EL34 a maximum figure? In the same way that all the valves in a parallel fed design pass different currents to suit the valve's purpose, all the valves in a series chain have different voltages but the current is 300mA for all of them, it is as simple as that.

Apart from any increase in heater power that might be needed in a series chain because if the heat insulating effect of increasing the heater cathode insulation voltage rating, the heater power of both series and parallel valve designs should be the same (although I've never checked the data and put this to the test!)