AC-3 output and outboard DAC

I have a Pioneer LD player that I also use for playing CDs. I recently purchased an outboard DAC to improve the CD sound from my LD and a DVD player. The LD player does not have any coax or optical outputs, but does sport an AC-3 RF output.

Is there any way to use the outboard DAC with the LD player, or am I stuck using the inboard processor for music reproduction? I have read about RF demodulators, but it sounds like these are for obtaining surround sound, rather than providing a digital output to a DAC for 2 channel stereo. Any thoughts?
I know that MSB used to make boards that could be installed to allow digital output.
Hi, I have a Pioneer LD/DVD player too, the DVL-91 I think it is, and the AC-3 out to the RF demodulator I bought here (a B&K unit) does not decode anything but movie soundtracks, no CDs.