Re: Manley and Royer mics with 12AX7.
Both of these mics use exellent capsules. One should be really "talented" to completely screw their sound.
The thing is--12AX7 is cheap and readily available, so its use in a modern mics is evident for reasons...
But...... just name at least one "classic" mic, which uses this tube. I don't think so, and this is most likely for a reason.
It is just not a good idea to use this tube with such a pure capacitive source as a mic capsule because of Miller effect. It is not a good idea to use such a high gain and high impedance tube because of transformer coupling issues.