[Chris Hornbeck]

On Fri, 13 Oct 2006 21:35:48 +0200, "Ruud Broens"
wrote:

: Since most of these assumptions are never wholly realized
: in actual tubes, the exponent (*always* given without
: caveats) generally differs somewhat from 3/2, being
: somewhere between 1 and 5/2.
:
larger than ^3/2 you'll have to give me an example of that ;-)

Maybe the most straightforward way to get a large exponent
is by variable grid spacing. An example might be variable-mu
tubes like 6BA6, etc. where nonlinearity is a design goal.


ECC83 Mazda gave ^1.12 to ^0.97 from 10 to 160V
in general, low current will spoil the "space current
dominates all" approximation quite a bit.

Linearity like this requires very careful work getting
tight and equally-spaced grid pitch. The great European
manufacturers knew more than just metallurgy; they could
build very high precision small things long before
modern computer control of everything. The linearity
of Telefunken and some Amperex 12AX7's is pretty amazing.

And probably not duplicable today. Don't know for sure.

Much thanks, as always,

Chris Hornbeck