The Dish Network User's Resource
It turns out that the DP has a circuit already in place for coaxial digital audio output-- EchoStar simply left out the connector, for whatever reason. Cost savings, RFI concerns?
They were thoughtful enough to provide a convenient pair of points to solder to, however. With the DP's cover open, look towards the extreme left-rear corner of its mainboard, in between the satellite tuner module and the phone jack. There should be two header-type solder pads, with no actual header pins installed, labeled “SPDIF OUT (COAX) -- J9”.
All you have to do is attach a small-diameter coax cable at this position! Connect the center conductor to Pin 1 (the squareish one, closer to the back panel), and the shield to the other position (standard round shape).
Doing this without removing the mainboard can be a tad difficult due to the close quarters. Be sure that both coax conductors (shield braid especially) are well-tinned first, to avoid shorts.
To get the signal out of mine, I just cut up a cheapo stereo patch cable (female RCA jack already molded onto one end), which was thin enough to run out through a ventilation slot. This could easily be undone later, providing you're neat about it. Some may prefer to drill out an extra hole in the back, and attach a panel-mount RCA connector there. Individual wires to the jack should be OK in this case, but try not to short the RCA shell (digital ground) to chassis ground in the process.
So, my DP is now driving about 50' of coax (RG-6) feeding a Yamaha receiver, with no signal problems whatsoever. Both Dolby Digital and PCM come through beautifully. Since the optical TOSlink port remains active as well, this would be one way to feed digital audio to systems in two different rooms