su6oxone, here's how I approach it, although I have no data to back this up, and I could and really should measure what I'm talking about here. In fact I promise to do so as soon as I can. But in the meantime ...
A stock Denecke PS-2 has electrolytic coupling capacitors at its outputs, while any transformerless preamp that offers phantom powering will generally have electrolytic coupling capacitors at its inputs. Electrolytic capacitors are fine as long as there's some DC voltage (of the correct polarity) across them. Take that away, though, and they may begin to add some distortion to a signal. (That's what I need to measure.)
The PS-2's output capacitors are kept charged by the phantom power supply itself, so no worries there. But the input capacitors of the preamp aren't, because (presumably) you turn off the preamp's phantom power circuit. So that's where the problem might occur, if it's a problem at all.
How I deal with it is that I own two PS-2s--one of which has had its output capacitors bypassed. This is a standard modification which Denecke can tell you how to do, or you can have them do it for you. I use that supply for situations such as you describe, while I use the other one with a Denecke AD-20 (a/k/a Zefiro InBox), since that unit's preamp can't tolerate DC on its inputs--it absolutely requires a phantom supply that blocks DC.
--best regards