Is there a problem w/ using both amp inputs?

I would like to connect my Berkeley Alpha DAC directly to my Levinson ML336 via balanced input. And for other analog sources, connect my BAT VK51se pre to the ML336 via the single ended inputs. Would this create any problems with both inputs connected at the same time? Has anyone tried this?
You need to read your manual and/or consult ML about this. If there is no balanced/unbalanced switch on the amp, it is very likely you cannot do what you propose as the two input will interfere.

Even if there is a switch, it may only be for the purpose of changing the input impedance appropriately and, therefore, preclude connecting both sources simultaneously.

Kr4 is right. The only thing I would add is that your BAT is fully balanced, why not just use it for everything? Its an outstanding preamp.
I have and it didn't work with my SS mono amps when both XLR and RCA inputs were connected to 2 different preamps. The volume was severely attenuated ... my amp is not balanced design so it's a pseudo XLR. I doubt it's in user manual so just try it out.
Thanks. I followed Kal's advice and contacted ML.

Here is their response:

"Yes, this configuration will cause problems and is not recommended; doing this will:
· Place the output stages of the DAC and the preamp in parallel with each other.
·Place an ‘uneven’ load on the XRL input.
While these conditions will probable not damage the No. 336 or the DAC/preamp the sound quality of all three will be negatively affected."