Plate resistor question

[fitz]

Forgive my drawn out, and likely dumb question.

I am looking at the tube data sheet for an EF86 tube. The data sheet gives typical Operating Characteristics for various sizes of plate resistors. Now knowing that I am wanting to eventurally place a C4S on the plate, should the design go with a large or small plate resistor ? Knowing that the C4S loads the plate with a very high resistance, I wasnt sure if there was a general rule to design the stage with an already large or small plate resistor. Or if it even matters.

[Paul Birkeland]

It's very, very important to use a plate resistor along with the C4S.  The plate resistor on the pentode is highly influential in determining how much gain you have, and the plate resistor is generally approximately the output impedance of the pentode stage. 

If, for instance, you would like to run the EF86 at 100V on the plate and 1.5V of bias with a 100K load (100K resistor to ground from the plate).  We know we need 2mA from the current source for plate current but also we need another 1mA of current to send through the plate loading resistor.   If the screen voltage is ~100V, I would expect a gain of 46dB (x200) from such a stage.