24-10-2023, 04:13 PM
(24-10-2023, 01:11 PM)Mike Watterson Wrote: There doesn't seem to be any taper on the construction and of course the valves used for effective AGC on g1 have a progressively wider spiral on g1...
No, I'd have been surprised if there was, imagining the production difficulties of it if so... And filament-lead swapping trials indicated otherwise anyway.
But a DH filament will always give a vari-μ effect. When the bias has increased to the point that a quarter of the current is cut off (at the positive end of the filament) then the remailing active length gives 75% of initial value of gm; more bias cuts of half the current so remaining gm is 50% of gm; and so on.
(22-10-2023, 12:15 AM)Jez Wrote: I'm hoping for virtually zero microphonics, noise way lower than any conventional pentode and amazing linearity...
I daresay they could be linear right up to inception of cut-off, but the mechanism above will always kick in
