You aren't really wrong in your comments about the tubes, although
there are some inaccuracies.  The dissipation rating of the 6L6 was 19
Watts I think, and the 6L6GC went up to more, perhaps 30 Watts.  The 807
had a five pin base and a plate cap but internally was pretty much the
same tube.  The plate cap enabled better separation of grid and plate
circuits, and thus operation to slightly higher frequencies.
 
There was a whole bunch of audio tubes in the 60s that were variations
on the 6L6, such as the 5881 and some other numbers that escape me.
Meanwhile there were variations on the 807, such as the 6146.  But
internally the differences were minor.  The intended use dictated the
physical arrangement but the electrodes were the same, a beam power
pentode with 19-35 Watts of dissipation.  The different ratings came
about from different ways of removing the heat, and perhaps minor
differences in materials.
 
So, for low frequency use, any of the tubes pretty much were electrically
interchangeable.  You may remember the 829B, which was a pair of them
in one envelope, with a glass base and two plate caps.  I used one for
years in a transmitter.  The 2E26 was smaller, perhaps more like a 6V6
in ratings, but with a plate cap.  The 832 was a pair of them in one
envelope similar to the 829B.
 
73 DE K6DDX
--- Maximus 3.00
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