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How do I make a digital coaxial cable?

post #1 of 6
5/7/09 at 3:29am
Thread Starter 
How do I make a digital coaxial cable (RCA type)?

do i just buy something like this coaxial cable: Belden CDT Inc Belden 1695A RG6 Plenum SDI/HDTV Coaxial Cable Bulk Digital Video Cable at Markertek.com
and solder it to some Eichmann bullets ( http://www.homegrownaudio.com/images...copper_big.jpg ) just like i would when making regular rca to rca cable? Then use another regular cable (jenna or hga silver wire) for ground?
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post #2 of 6
5/7/09 at 3:57am
The idea is correct. but the termination is key - make sure your soldering skills are good.
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post #3 of 6
5/7/09 at 4:03am
Yep. You need a 75 ohm coaxial cable (which that one is). Ideally you would use 75 ohm connectors like F or BNC connectors. No RCA connector is 75 ohms, they're about 50 ohms. That being said, they do work. The Eichmanns are fine.
What would you need another cable for? The center conductor of your coax cable is soldered to the positive pin and the shield is your signal return. The shield has to be connected at both ends for the cable to work.
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post #4 of 6
5/7/09 at 11:25am
Thread Starter 
well my prelude only has coaxial and toslink or else id use BNC. also so i just solder the shield to the ground? I dont have to use anothe cable for ground?

this will be for outputting to a dac in the future.
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post #5 of 6
5/7/09 at 12:59pm
here's a thought:

comcast provides really good cables (18AWG RG6, 75 ohms) and connectors (at least in my area). if you have one sitting around, then get two of the RadioShack coax to phono plug adapters. voila! an RCA terminated coax cable usable as digital cable. yes, it works.
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post #6 of 6
5/7/09 at 2:48pm
Quote:
Originally Posted by Baird GoW View Post
well my prelude only has coaxial and toslink or else id use BNC. also so i just solder the shield to the ground? I dont have to use anothe cable for ground?

this will be for outputting to a dac in the future.
Yes just solder the shield to ground. Unless you have horrendous amounts of RFI there won't be any problem. The standard characteristic output and input impedance for digital coax (and composite video) is 75 ohms. If your cable matches that impedance, then you will have no effect on the signal from cable resistance. The effect of 50 ohm rca connectors is very small.
If you add another cable for ground, then you are increasing the characteristic impedance of the cable which can lead to increased signal resistance and noise.

EDIT: I've used a Belden 1695a cable for digital myself (with Canare connectors). Worked fine.
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