[Milsurplus] 12A6 questions

[Jack Antonio]

So, what exactly is the story behind the 12A6? Doesn't
seem to have any use at all outside the military world.
But it sure seems to have been the 12V audio pa tube
of choice for WWII radios.

What was the requirement for the 12A6 that designers couldn't
have used the 12V6 or some other 12 version of a 6 volt tube?

Which of the 6V power amp tubes, 6K6, 6V6, 6W6, etc, is the
closest type to replacing the 12A6?  Some of the conversions
I have seen involve changing the cathode resistor.  Is there a
direct replacement?

Just curious

Jack

Jack Antonio WA7DIA
scr287 at sbcglobal.net