Jeff, I have never used them, people who bi-amp sometimes need them to connect two amps to one preamp. The big full line cable/connector companies like Monster Cable, Vampire etc should have two types available: 1)audio y adaptor which has 1 male RCA with very short "y" cable to 2 female RCA, this type may be necessary if you have crowded conditions with no room. 2)also have splitter/y adaptor all in one piece plug, this would be the best way if you have room to connect cables. Monster charges $15 for either model
Of course your local Radio Shack has them, if you use one piece plug gold plated maybe their is little sonic difference.