"Nick Gorham" wrote in message
...
Arfa Daily wrote:


Perhaps someone who purports to know the difference could enlighten me,
as I really am interested in knowing.

Arfa

Well, I don't purport to KNOW if there is a difference, but one thing
comes to mind. Once the makers start to use a cathode, which is effectivly
a rigid cylinder, then the grid to cathode spaceing can be much reduced.
Ending up in the 50's with the very high gm frame grid valves like the
e810f and d3a. The DH valves, because of its "floppy" fillament needed to
keep the first grid out of the way. I wonder if this is in part the cause
of the difference. Its certainly the case that IH valves seem to show far
more of the island effect in their curves. You only have to compare (for
example) a 2a3 and a triode connected 807 to see the difference, and this
effect is a direct result of grid to emmiter spacing.

--
Nick

OK Nick, thanks for that. It's valid and useful input, and a situation that
I hadn't considered. I will ponder further ...

Arfa