Andre Jute wrote:

Ian Thompson-Bell wrote:
I have being playing around with plate characteristics graphs, looking
at how basic parameters (gm,rp and mu) vary with operating point. The
most frustrating thing about this is that the published curves all
extend to rather large plate currents and voltages. For my preamp I am
working at plate currents of less than 5mA and the curves here are
rather cramped. Is there any source of curves that are expanded for the
lower plate current region?

Cheers

Ian

After a search lasting only an hour and a quarter (my filing system
must be better than I thought) I have in my hand a sheet of Ia-Eb-Eg
curves for a 6SL7-GT.

Thank you for going to so much effort.

It is clearly an enlargement from another
document. Unfortunately I can't tell whether from another sheet, a
book or a computer file, except that the file isn't presently on my
computer, so the source is a mystery. However, it is precisely the
sort of thing you want. It looks like a normal set of transfer curves,
with two exceptions: that on the left the plate current scale runs
from 0 to 2A and on the right from 0 to 8mA, and that there are two
sets of curves on the sheet, one hard lines, one dotted lines. There
are thus such curves available, or at least in one case, the 6SL7-GT.

That sounds just like what I need.

If it is the tube you're actually working on, I should be happy to
photograph the sheet I have and post it on my netsite for you to
download, print out and use as graph paper.


Unfortunately that is not the tube I am using. I am using a 6AU6 in
triode configuration.

Cheers

Ian