I would like to find out what the maximum recommended wiring runs are for 1) spdif coaxial audio cable 2) hdmi audio video cable What I am trying to do is send both audio & video programming from by desktop PC to my home theatre system. I have both spdif & hdmi outputs from my pc. My home pc is located in the den which is next to my family room which houses the home theatre system. My AV receiver is a Denon AVR3805 which is not equipped with hdmi input. My intention is to run spdif audio direct from the pc to the AV receiver and hdmi direct from the pc to the HDTV. I think the entire run will be less than 15 feet but I would probably use a 15ft length of cable to ensure that I have enough length. Would such a setup work and should I expect signal degradation? By the way, I love the monthly news letter and never miss an issue. I appreciate your advice and the way you bring the technical aspects within reach for the average Joe.

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Hello Gord,

Thanks for your compliments on the Axiom newsletter--it's great to get feedback from readers. Generally speaking, you are usually OK to run digital coaxial cable for three or four metres--12 to 15 feet--without drop-out problems. I'd normally cite about 15 or 20 feet as the maximum for a run of HDMI. However, in both cases, there are a number of unknown factors operating which are dependent on the quality of the little digital and HDMI "sending" devices in your desktop PC, as well as the robustness of the digital coaxial "receiving" circuits in your Denon AVR3805 and in the HDTV.

Although there are millions digital 1's and 0's sent along spdif and HDMI cables, we are still talking about a low-level voltage sent through these cables. In digital terms, you'll either get perfect digital audio and video with no audible drop-outs or video "freezing", pixelation and other artifacts---or not. You won't hurt your equipment by trying it. It will either work well or it won't. That's the great thing about digital--it either works perfectly, or it doesn't work at all. It's wise to buy upgraded cables for these applications. I just posed the HDMI question over lunch to some colleagues at a recent show, and the consensus was "15 feet or so. . ." with lots of "it depends. .". One guy at the table, who lived in Brooklyn, NY, described how he ran an HDMI cable through the second-story window of his house down to the first floor with no problems.

Regards,

Alan Lofft
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Alan Lofft,
Axiom Resident Expert (Retired)