I've never used 2 pots, but if I did, I'd probably want to
do something differnt insted of the individual bias
adjustments. I'd personally want to have 1 to set the
overall bias level, and another set up (say a 500k or a
1meg pot, with each 'leg going to the grids, the wiper to
the bias feed, and a pair of 220k-470k resistors -- one
from each 'side' of the piot to the wiper... sure it would
make the respsonse of the pot non-linear, but it would
give you a balance with a built in safeguard. (the
resistors would also keep one tube from running away
if the balance was turned too much in favor of the other
tube. I'd most likely set the pot for the middle, and set
the bias with the amp open, and let the balance be a
panel mounted pot, sort of a balance that could be
tweaked while playing to get the minimal hum, and set
the balance on the fly to change the tone... then agian, I
wouldnt put this on a production amp... too easily to set
the amp up REAL hot, then tweak this and take out a
tube at a time... second thought.. might not be a good
idea.. nevermind..I"m rambling *laugh*