Newbie question: What characteristics are best for a cathode follower?

[kodabmx]

6N6P is overkill for a concertina IMHO. I can drive 200+V into triode strapped sweep tubes with 6SN7 fed by 6F12P concertina/cathodyne/split-load phase splitter (I wish we could all settle on one name for it).

I do use 6N6P to drive headphones OTL though.

 

[6A3sUMMER]

For selection of a tube to be used as either a Cathodyne, or for a Cathode follower . . .

One thing to remember is the Filament to Cathode maximum voltage ratings.
AC, DC, Peak; in both directions (filament + versus cathode; filament - versus cathode).

Then, consider both the quiescent cathode DC voltage, and the required + and - peak swings from that quiescent DC voltage.

Also be sure to take into account the changing voltages during warmup of all the tubes in the circuit.

Some filament to cathode voltage ratings are 60V, 100V, 180V.