What is Unique about "Coaxial Digital" Interconnects? (1 Viewer)

[Brent Hutto]

I just had an HDTV-capable cable-TV box delivered. It has a coaxial digital output but the only spare digital-audio cables I had were optical. I used an old, spare RCA-type audio interconnect to hook it up to my home theater receiver. I'm not inclined to go spend 20 bucks on a "digital" interconnect since it works fine. Is there any fundamental difference? This is a very expensive (you know, oxygen-free multiply-shielded, gold-plated super-duper) interconnect that I have left over from the old days when I had a decent stereo setup.

 

[Bob McElfresh]

They are essentially "Video Cables".

All video cables must be made with something called "75 ohm coax" and this is what they had in mind when they designed the coaxial-digital specification. Many audio cables are also made with 75 ohm coax this, but "50 ohm" coax is more common.

So it's a gamble if you use an ordinary audio cable. Is it 50 ohm or 75? The 'wrong' cable will actually appear to work. But people report audio drop-outs. Sometimes it's once every 15 minutes or so, other times it's every 2-3 minutes. The problems were all solved when they replaced the audio cable with a video cable for the coaxial-digital connection.

As long as you dont hear occasional drop-outs in the audio, you should be fine.

 

[Brent Hutto]

Thanks, Bob. The cable of course is unlabelled w.r.t. impedence, although I always thought of them as 75-ohm cables and didn't realize anyone used 50-ohm audio cables.

At any rate, the TV was on the HDTV channels for most of the period 5:00PM to 9:30PM last night and the only time I noticed the audio going aways was during the change from program to commercial and back. I'm pretty quick to notice such things and was in hyper-critical mode checking out the new box so it's almost surely working fine.

As it turns out, I need a cable about six inches longer than the ones I have in order to clean up the wiring so I'll probably end up buying a longer digital-audio cable at some point. It's good to know my audio ones work whenever I need to fill in with one. Now I can put off buying one until I get around to dressing the cabling mess -- might be six months as much as I hate that job...

 

[Bob McElfresh]

Some advice on dealing with 'cable clutter':

- Put the receiver/amp on the lowest possible shelf. This lets the speaker wires flow out away from the other components.

- Pick a side and pull the power cords for all devices in the rack to this side. Use velcro ties to bundle them together or spiral-wrap.

- Now you can just leave the interconnects to dangle down the middle or loosly bundle them with 1 or 2 velcro straps. You dont want to tightly bundle them or the entire thing becomes a weight dragging off all those friction-fit connectors.

- I also recomend putting the components you interact with on the upper shelves so you dont have to bend to use them. Put remote-control-only devices above the receiver.

For 'low quality' devices, Radio Shack and Monster sell bundles of Left/Right/Video or Left/Right/SVideo or Optical/SVideo, etc. One thick cable is preferable to 3 individual cables.

 

[Brent Hutto]

Good advice, Bob.

My situation is a little different because the HT receiver is on a shelf all by itself beside the TV. The shelves under the TV didn't quite have enough room for the receiver along with VCR, satellite (now replaced by cable box), and DVD player. The Sony stand has a hollow cable tray running up the back that hides the interconnects between the stuff under the TV and the back of the TV itself. Very handy although not the easiest thing to take apart and put back together when adding equipment.

What has really worked well for me (in addition to the combo cables you mention) are those sections of black plastic "drain pipe" material with a slot down the side that Radio Shack sells. I use one of those to get all the power wires to the surge supressor on the wall and another for the stuff going to the right-front speaker and HT receiver (which are close together). All that actually runs to the HT receiver is a L-R audio cable from the back of the TV and the coaxial digital cables from DVD player and cable box. I don't switch any video with the reciever since my TV has lots of inputs.

All that really shows is three of the five speaker wires, the subwoofer cable and then a couple feet of each wire after it exits the "drain pipe" near its destination. I'm surprise how clean I was able to get everything without too much trouble. I highly recommend the "drain pipe", whatever its real name might be.