What are you trying to do? I think you are trying to go from unbalanced to balanced. Is that correct?
If you are going unbalanced (RCA) to balanced (XLR), then pin 2 of XLR to hot of RCA, and pins 1 and 3 of XLR to ground of RCA. That is how it is done, and it is called a floating line. You need one cable for left and one for right.