Long-distance Digital Audio

August 1, 2005 1:31 PM

Audiofilter: What is the cheapest way to get pure digital sound from a computer 10~15 feet away from a surround sound system?

I'm running a 25 foot HDMI cable out of the back of my PC for video, which is snaked up around the wall to travel 15 feet into the back of my HDTV. I've just bought a new surround sound system, which works absolutely fantastic, but I'd like to get digital sound out of my computer and into the back of the receiver. The only two digital options for inputs on the back of the receiver is TOSLink and digital coxal cable. I'm looking to buy a new sound card for the PC anyway, so it will have at the very least TOSlink and digital coax. I know TOSLink doesn't like to be fooled with too much (too many strange angles will break the fibers), and they both seem to be really expensive at lengths >12 feet.

I'd rather not pay hundreds of bucks for cable. The 25 ft HDMI cable I bought cost about 40 bucks, which is around the amound I'm looking to spend on audio cable.

I was thinking ethernet cable may be an option, because it's digital, cheap and snakeable. Is this idea foolish, or are there people hacking audio adaptors for ethernet cable?

What is the best way to go about this?

posted by SweetJesus to computers & internet (5 answers total)

5m USB cable + USB sound card + normal length TOSLink.
posted by cillit bang at 1:39 PM on August 1, 2005

Fuckin' brilliant, exactly what I'm looking for.
posted by SweetJesus at 1:41 PM on August 1, 2005

Have you done any research on really long spdif cables? I would bet you can get away with 15ft of coaxial. As long as your cable is impedance matched with the connectors it is attached to, you should be able to get away with pretty long runs. Just look for coaxial cable with 75ohm printed on it, put your own connectors on, and see what happens.

You can probably also get 15ft of toslink pretty cheap, but the signal might degrade quickly on a cheap fiber optic (I don't have any experience with this at all. In the late 90's people were saying that toslink is significantly worse than coaxial).

In any case, AC-3 and DTS signals should be pretty impervious to the cable you choose. If you are driving a stereo DAC with PCM audio you will have to be more careful, especially if it is an old DAC that doesn't re-clock (jitter is evil).
posted by Chuckles at 2:48 PM on August 1, 2005

ditto what Chuckles said. it's going to be cheaper and more feature-rich to use a regular PCI sound card with a long coax SPDIF than to mess around with USB sound interfaces (and long USB cables).
posted by rxrfrx at 6:31 PM on August 1, 2005

I use a 30 foot toslink cable for exactly the same purpose. I got it custom-fabricated for under $50 in 1999 from a place in NJ that I ordered from on the internet.
(something like this)
I've been very happy with it since then.
posted by Four Flavors at 9:10 AM on August 2, 2005