I have used gold plated RCA adapters from Radioshack to join 2 of the same cable to make longer cables and never experienced any sound degradation. How long though are you going to extend the cable? IME with using adapters I've only extended cables to either extend the length of my turntable cables, or from preamp to amp which was just another 3-4 feet of wire. Those were the times when I had no sound issues. Another time I used these adapters to extend the length of my subwoofer cable and had no issues there either. I joined 2 6ft cables.
