[Alex]

"flipper" wrote in message
...

However, R11 decouples C9 + 1N5GT plate capacitance + wiring capacitance
from the grid of V1AA, thus helping stability. Thus, you are right, R11
may
be beneficial, and I am retracting my advice. Let R11 be there.

Hmm. I'm not sure I follow. If it weren't for FB R11 wouldn't normally
be there anyway so you'd have the C9 + 1N5GT plate capacitance +
wiring capacitance coupling. So why is FB to that point any worse than
if, say, you could take it to the pentode cathode (meaning the grid
and capacitances are in the loop)?

In short, if you worked with op-amps, you know that loading "the summing
junction" (inverting input) with capacitance is generally a bad thing for
stability. In your case the grid of the triode where the feedback R10
resistor is connected -- is the sort of the summing junction (inverting
input). It is better avoid capacitive loading of it.

However, in your case since you have a small phase advancing cap in parallel
to R10, loading the summing junction is not that bad. In any case, if you
remove R11, it is good also to remove this 47pF (or reduce it).