Krell FPB 600, XLR short pins

Does anybody uses the RCA input on the Krell FPB 600? Do you short out the XLR input with shorting pin, if yes, how? I have tried to use the RCA input but I am getting humming from both speakers, it was fine with balanced input.
Insert the U pins between pins 1 and 3 of the XLR connectors and that should take care of the humming problem. I had the same problem and the shorting pins really helped.
Thanks Sfstereo, I will try it.