The three most popular High Gain 12AX7 tubes are:
# 1) Warm with mild COMPRESSION and early distortion
GAIN for the critical first gain stage.
PRIVATE STOCK When available. For use as a gain stage tube. These are the 1 in 200 tubes you hear about. Unusually high performing tubes, the very best of a lot.
# 2) Bright with slight COMPRESSION and slight distortion