Two preamps into one amp?

I did this yesterday with my Schitt Wotan amp in my office. I now have my Benchmark HPA4 preamp  (RCA) and the Schiit Kara F preamp (XLR) going into the Wotan. The unique thing about the Wotan is that the RCA and XLR switch is on the front of the amp. This toggle switch can also be controlled by my iPhone.

My Benchmark HPA4 preamp now has a 25-foot XLR going from my office to the Livingroom where my CODA #16 amp resides. Yes a little crazy.

The CODA #16 also has a front facing toggle switch for RCA and XLR, though I am only using the XLR.

Thanks -- just as I hoped. The Coda amp front panel input selector feels like an invitation for two preamps, or one connected both ways, so I will proceed.  

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

what could go wrong?

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.