For several years I have been trying to access the digital audio output from my Comcast Motorola cable box with no results. It's output seems only to be 5.1 Dobly Digital, which is not compatible with a normal audio stereo DAC's input.
My most recent cable box is a Comcast labeled Motorola DCH3416 and that has given me no better results than with previous models.
The goal of course is to bring the digital audio out ahead of any of the D to A converters in either the cable box itself, or in the big high res Sony TV that it drivers. I wanted to feed the digital audio into my own Vision DAC, and on to the rest of my two channel HT setup; Insight+ preamp, Ultravalve power amp, and a set of Salk Songtower speakers. I was certain that the best audio I could get previously was pretty crummy as to what I was expecting if I could bypass the built in DACs in either the cable box or the TV itself.
Finally yesterday I achieved my goal, and I gotta tell you that my HT sound is now way better than I had expected. I suspect that other approaches to good audio from HT setups are not even close.
Making the project finally work took two new pieces of equipment and a lot of trial and error and good support from the provider of the necessary equipment, Atlona.
The main new piece of hardware is an Atlona AT-HD577 de-embedder and HDMI switcher.
This unit has two sets of switchable HDMI inputs and an HDMI output. It also has digital audio outputs, both coax and optical. It can strip out the digital audio signal from a HDMI digital video/audio source and provide high resolution digital audio output while passing the HDMI signal through to your video monitor.
It is very useful in extracting high resolution digital audio from SACD and DVD-Audio discs played on my Oppo Blue Ray player.
However, the HD577 alone did not allow me to use it with the Comcast box. The HDMI pass through did not sync with the TV. The result, no useable image on the TV screen, and also no digital audio output.
After a consultation with Atlona, it was recommended that a second Atlona piece of hardware was required too, their HDMI EDID Recorder-Writer, model #AT-HDSync.
This little unit goes in series between the HD577 HDMI output and the TV monitor, again, both connected with HDMI cables. The setup requires connecting the HDynnc to the TV monitor itself alone, and switch it to allow it to read and permanently remember the EDID info from the TV. Then the HDSync unit is switched to one of its use positions, and then connected to the HD577 and voila! TV video sharp and clear.
Unfortunately still no digital audio output from the HD577.
That took more help from Atlona tech support to discover a hidden menu built into the Motorola/Comcast cable box. I had previously gone through the Motorola manual carefully and found no way of dealing with its digital audio output. However, on screen, the menu options had an obscure item I tried and actually located a sub-menu dealing with its audio preferences. It was set for "Auto". There were options for "passthrough" and some other unfamiliar digital format. I switched the setting to the digital format.
After years of messing around with this, finally, useful digital audio output from the Atlona HD577 box, along with great video output too.
There are still some bugs with the setup, yet to be resolved. If I switch the Atlona de-embedder from its HDMI output used by the Comcast box to the other one and then back, it looses sync with the TV. I have to cycle the Atlona boxes on and off to restore function.
A further mystery is that when I use the Atlona de-embedder with my Blu Ray DVD discs with my Oppo Blu Ray player, I get excellent video and digital audio quality from the Atlona, but it looses the front center channel vocal tracks. It is as if it is stripping the surround sound channels from the Blu Ray audio but not the main stereo or front center vocal tracks. Performer's mouths move, but they don't say anything I can hear. (With some movies, that is not all bad.
Atlona says they will investigate these bugs further. They have been very helpful so far.
Meanwhile, I am experiencing the best cable TV audio I have ever heard and have access to high res audio from SACD and other high bit rate HDMI sources too.
The two boxes combined will cost me about $400, but they are keepers for sure.
Frank Van Alstine