As a routine in service rounds it was common to change out the the 12AX7A's at a rate of 2 to 1, time wise, vs the 12AT7. The AT7 is just that much more rugged a tube.
I don't know if the 7025 is made any more. It is the low-noise/hi-mu version of the AX7. If we could get out hands on these, they always got put in the signal path.
I don't know if the 7025 is made any more. It is the low-noise/hi-mu version of the AX7. If we could get out hands on these, they always got put in the signal path.