RCA to balanced XLR - will this work on a DSP?

[antcollinet]

That's mostly correct, but only when used in balanced interfaces on both ends. As for terms, differential input is the name for the technique to read a balanced output through XLR-cable. But please note, that ground can be wired to travel through any pin or even 2 pins of XLR-cable, if the source is single-ended (per this topic) and differential input can be used like that. And most likely there is gear with XLR outputs where either pin 2 or 3 is ground, since that is allowed by definition.

But note that the intent of the OP is not to have a single ended source, but to create a stereo differential signal using the 4 outputs of the flex, with two of the outputs inverted to provide the "cold" signals, while the other two (non inverted) are the "hot".