<font color='#000000'>I have had good luck with getting Dolby Pro logic from the digital cable box's coax feed.
In addition, even using coax from a digital cable box, you will only get Dolby Digital on certain stations, with certain programming (usually movie channels, and only on more recent movies.)
I'm not sure how well Dolby Pro Logic will show up on standard RCA outputs from a regular cable box, I would suspect that it would be intermittent.</font>