Question about B&K M200 Monoblock inputs

I'm hoping someone can help with a technical question. I have a B&K M200 Sonata mono amp.  This unit is a newer design than the original M200s - the heat sinks are inboard the chassis. It also has 2 XLR inputs, 2 RCA inputs (not 1), and 2 sets of speaker outputs.  One of the XLR's is not connected to anything - it's simply installed in the rear panel with no wiring inside. The speaker binding posts are paralleled - fine for a mono amp.  The concern is the 2 RCA inputs are wired in. They aren't perfectly parallel, but have a small resistive decoupling between them, and also a capacitive decoupling.  I can't see exactly how they are wired. The question I have is is there some kind of primitive passive mixer circuit built into this input. I assume if they were paralleled it would be bad to connect a 2 channel source to these inputs . 

thanks in advance.