You need two cables. A composite or S-Video cable to carry the video signal and a coaxial cable to carry the AC3 signal. In my house the audio rack is about 75 feet froom my PC. I bought a roll of RG6 coaxial cable, cut two pieces to length, terminated each end with F connectors, and screwed F to RCA adapters in the ends. Retail cost for these parts is about $35 and they are readily available at your local Radio Shack or radioshack.com. Make certain you purchase an AC3 receiver with at least one coaxial digital input.