How long can digital coaxial cables be?

[jason978]

hey gang,

Because I can't put my receiver near my dvd player(space restrictions), I need to use a 25 ft cable to connect the dvd player to the dd/dts receiver. Can I use a dig. coax cable this long? If so, where can I find one? I was planning on using a video rca cable for this but have not been able to find one that long.

Why do people say to use video rca cable and not audio rca cable?

PS:
the dvd player is connected directly to the tv via s-video cable.

[This message has been edited by jason978 (edited November 27, 2000).]

[X]

I would think 25' would not be a problem. You'd find out pretty quick -- either it would work well, or it wouldn't. You need video cable (75 ohm), not audio cable, so you might find some video coax with "F" type connectors and then use F -> RCA converters that you can get at Radio Shack. There's probably other places you can the the premade cable with the right connectors though.

[catware]

The specs on the length for the digital optical cables is 10m for the Toslink (plastic based) cables. However, usually you can go to 15m with no problem, but 20m will not work.

Using regular fiberoptic lines (glass based) you will be able to go hundreds of meters for a digital audio connection due to very small signal attenuation per unit length.

More specific to your situation, I believe a digital coaxial connection is also only spec'd to 10m, but I'd imagine it would go much farther than the optical Toslink link. The output voltage is around 3 volts, if I'm not mistaken.

I have an el cheapo 40' *unshielded* 20gauge speaker extension wire I am using to run a digital connection from my computer to my receiver, bought because was $5 and came with an RCA connector on each end. I experience a pop every minute or two, but it could just as easily be from a problem with my custom sound card conversion or a grounding problem than the wire itself.

For your purpose, bottom line is 25' (or 7.5m) of shielded coax will work fine for a digital connection. However, I might suggest you use an optical connection to avoid any grounding problems, since the devices will be in different outlets and problably different circuits.

Here is a place in Edmonton, Canada that sells plastic optical fiber with Toslink connectors at a price of $2.50 per meter, or less than $20 for your application (look halfway down the page):
http://www.sys-concept.com/fiberoptic.htm

To answer your other question, the only reason a video cable is recommended (but not required) over audio patch cable is it usually has better shielding. Folks, this is a digital connection, i.e. a square wave. Chance for interference over usual patch lengths of 1-2 meters is imperceptible, especially since we are talking about multiple volts here, not millivolts. Any wire can be used.

[This message has been edited by catware (edited November 28, 2000).]

[ZenDog]

I needed a 30' run of 75ohm RCA cable for my sub, but Radio Shack didn't have any that long. What I ended up doing was picking up a pair of 20' RCA cables. I pulled the two RCA cables apart and connected them with a gold plated RCA coupler. This worked perfect for me and only cost the pair of RCA cables and the coupler.