I recorded the DC_coupled preamp's Phantom Turn On and Turn Off Characteristics.
DC Coupled Preamp Phantom Turn On Turn Off Characteristics
The microphone used was an Audio Technica AT3525.
The timescale is 500 ms per major division.
The first event is phantom turn-off. The preamp recovers in about 2.5 seconds.
The second event is phantom turn-on. This also takes about 2.5 seconds.
This includes the time it takes the mic to wake-up and stabilize.
At the end of the turn-on tail there is usable audio.
This is transformer-like performance.
An "active" mic preamp that was capacitor-coupled with 47 uF electrolytics could easily take 15-45 seconds to produce audio and a couple of minutes
to produce low-noise audio.
The point is not how quickly the DC-coupled preamp turns on and off, but more importantly the speed at which both the common mode and differential servos work.
0 to +48 and audio in 2.5 seconds including microphone.