Friend Rick at www.uneeda-audio.com mentions:
Phantom Power and TT/TRS Patch Bays
If you're building a studio, this is a bad idea. Avoid it.
Use XLR connectors instead. Yes, they're not as high density as a TT bay. Don't hot patch microphones when the phantom powering is turned on. Turn the phantom power off first. Even this may not be sufficient.
The problem is that the tip of the plug can contact ground as the plug is being inserted. With a transformerless input, this can discharge/charge the input blocking capacitors thru the microphone's output transformer. This could magnetize the core of the transformer, zap a ribbon microphone, or (remote possibility) damage a dynamic microphone.
With a transformer coupled input, you risk magnetizing the core of the console's input transformer, ruining its distortion characteristics.
If the microphone's output is transformer coupled, the microphone's output transformer could also have its core magnetized, ruining its distortion characteristics.
This is not good.