75th heap mighty scarce there pale face.
Big Chief in the sky not more cause 75th to rain down on little injuns.
Translaton, good 75ths are as scarce as hen's teeth Derb.
Jack OM, is the problem that you can't get the bias voltage down, or that the voltage is unstable?
How about a VR tube stack?
Is the range you need really -20 to -100, or did you pick that so you could fine tune the bias voltage?
I didn't think the 100th were that picky about bias, get it close and it should work.
If you really want to go silicon state, what about a zener stack, you could series up several, pick off the voltages at the appropriate place.