I think that it should be no problem, although I am no expert. Anecdotally, though, I asked Jerry Chamkis (the Aerco MP-2 maker) a similar question (could I run the RCA outs on my Aerco into the XLRs on an R44), and he said XLR inputs "work fine with unbalanced signals as they are a subset of balanced signals. The 'other' pin (Pin 3) is simply grounded."