Bill M wrote:
I'm a little confused again.

Setting up a 1624 tube for cathode biasing and also need to create a
center tap for keying to ground.

The book says 610 ohms at my voltage. So would I use a pair of 1200 ohm
resistors in this case?

My logic is since there is not a separate cathode then the two R in
parallel would raise the filament 'cathode' 600 ohms above B-minus.

TIA and Merry Christmas,

Bill
If the tube filament is running on AC then a resistor from the
transformer winding center tap to ground would do the job. If the
filament winding isn't center tapped, then two resistors form the center
tap. Usually two low ohm resistors (say 22 ohms) are used with a third
resistor to ground for the cathode bias from the junction of the two
resistors.
You could just use two larger resistors as you suggest, but in the case
of an audio amplifier how would you bypass it with a capacitor? (use TWO
capacitors).

If the tube filament is running on AC then the problem is compounded
since you might not be able to isolate the filament supply from ground.
Guess battery operated radios used C batteries.