OK, Phantom power is easier than I thought:
I built something like this today in a little box, and it works well, giving about 6 to 9 dB extra gain, and for some mics a little more top end. Test were done with a Grampian GR2L (30 ohm) ribbon, a Melodium 42b (200 ohm) , and another unidentified ribbon, of which I posted here recently. Test preamp / mixer / headphone amp is a Yamaha 01V96 mixer.
I tried a few pairs of transistors, and found that the quietest in my parts box were a couple of MP2222. I matched these by hfe, and matched the pairs of resistors as close as I could. The noise seems to be better that cranking the preamp by the same amount, especially at the top of its reach.
With the bias resistors matched the base voltages were identical to the nearest millivolt, so I removed the input caps. Are there any issues with sub-millivolt DC across transformers? The circuit works just fine without these & I can't hear any problems. So long as there isn't a voltage difference across the tranny the ribbon should be safe.