Two preamps into one amp?


Any reason why I shouldn't connect preamp 1 to balanced inputs of CODA S5.5, and preamp 2 to unbalanced inputs of the same amp, given that they won't operate simultaneously? Never tried this with any amp, but can't remember why not.

hickamore

It’s all good until the one time you forget to switch the input selector. 

To take it seriously: what happens to the amp if both inputs are driven simultaneously (by different signals from separate preamps)? Might there be a protection circuit? What if there's not?
The front panel input selector seems an invitation to risk this, yet the manual provides no warning on the subject.