I'm not sure what amps you are talking about, but aren't most amps that 
run say 572s or 811s grounded grid? YOu drive the cathode, and the output 
power is actually the power of the rig plus the amp.  Would you have grid 
current in a grounded grid?  Maybe it has been to long since tube theory.
73
Butch Bussen
wa0vjr
open Node 3148
Las Vegas