Robert, Philip is right on. RF demodulators are only for Dolby Digital soundtracks. In fact, they are often referred to AC-3 RF demodulators. The back panel of the 'D406 has an AC-3 RF output. You run a coaxial digital cable from this output to the AC-3 RF input on the demodulator and then an optical digital or coaxial digital cable from the demodulator to your pre/pro or receiver. I used to own the 'D406 and a Sony MOD-RF1 demodulator and this set-up worked great.