The most convient solution is to search for an RF demod that has switching between AC-3 and PCM. Sony, Pioneer, and Kenwood have made such models. Two inputs, one output.

The JVC JX-100 passive video switcher would work well in the previously suggested scenario.

Another solution is contingent upon your reciever. If it lets you choose video and switch the audio in from other inputs. I'm also presuming you're fresh out of digital inputs. Put an Audio Authority digital switcher on one of your recievers digital inputs, let's say DVD. Then hook up both players into the switcher. Another variation of this would be, if you have an extra video input on your TV. Again using the Audio Authority for the LD player's PCM output, use two different signal paths for LD. AC-3 and 1 of them thru the reciever as usual. Take the other video out into TV directly. Use the AA switcher to do DVD (or whatever, sat.,MD, ect) and LD sound.

The advantage to this approach is you'll have more digital inputs for your reciever, which I think only has 2 or 3 total. One last set of options would be to listen to non-AC-3 material out of the player's analog outputs or ditch AC-3 for the time being in favour of using the player's PCM digital output only. I'm a heavy-duty LD user myself, but as time goes by I care less and less about AC-3 on LDs. Most AC-3 LDs have now been released on DVD with 5.1 flavoured sound, either AC-3 or DTS, or both. PCM music or films with PCM stereo, Pro-Logic, or mono sound grand to my ears! I hope I stirred up some solutions, good luck with it, Rachael!