Rotel RB 1090 rca & xlr connection

Is it safe to connect rca and xlr to the RB 1090 at the same time?
For example: DVD -> receiver -> poweramp using rca (for movie)
PC -> DAC -> preamp -> poweramp using xlr (for music)

Probably, but I don't think we can be completely certain.

This Stereophile review indicates that there is a switch to select between the xlr and rca inputs.

My first concern is that if the switch position is changed while the amp is powered on a large transient might be sent to your speakers while the setting is being changed. That would be dependent on the design of the amplifier, and possibly also on the design of the components driving it and on whether or not they are supplying a signal at the time.

My second concern is that while most likely the switch simply disconnects the internal signal path from the unselected input, it seems conceivable to me that the design might short the unselected input to ground, to minimize the possibility of noise or crosstalk. If that were the case, the component driving the unselected input would see a short circuit on its output, which in many cases would not do any harm, but with some designs might cause damage or degradation of long-term reliability.

Another possible issue, although it is not related to the possibility of damage, is that if both sources are playing at the same time you might get objectionable levels of crosstalk from the unselected input to the selected input. That's obviously easy to check, by selecting one input while a signal is being applied only to the other input.

But in view of the first two possible issues, I personally wouldn't want to take any chances without further information on the specifics of the design.

-- Al
I have done this to compare the two inputs with some similar mid-grade interconnects (I couldn't hear a difference in sound quality or volume). Switching the little toggle back and forth does not create any snaps or transients in the line. I do not know about long term use, but for a temporary simultaneous connection I had no problems whatsoever.