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Old 12th February 2004, 10:07 PM   #1
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Default S/PDIF over long distances

A friend wants to connect the digital output of his Sound Blaster Live in his bedroom to the receiver in the living room. The length of the cable would need be between 50 and 75 feet.

Is this doable? He's looking for a simple and cheap solution.
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Old 12th February 2004, 10:59 PM   #2
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that's a long run, for networking they use repeaters for such tasks.

You won't make it with a single wire.
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Old 12th February 2004, 11:18 PM   #3
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He can do Toslink. Would that be better? I've always been under the impression that it was inferior. Still so?
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Old 12th February 2004, 11:37 PM   #4
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IMO is fiber better then coax, no EMI, no RI and fiber doesn't generate interference that disturbs other cables.
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Old 12th February 2004, 11:57 PM   #5
tiroth is offline tiroth  United States
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It should work fine. I used a Live! output over 50' with no problems.

Toslink, on the other hand, is a bad idea at that distance. (in addition to being inferior in general)
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Old 13th February 2004, 12:24 AM   #6
jwb is offline jwb  United States
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People, please. Think! before you write your post. Absolutely nobody uses a repeater for a computer network of only 50-70 feet. A category 5 cable installation has horizontal runs up to 295 feet and operates at 100MHz. A category 6 installation tops 250MHz at the same distance. And this is all with UTP.

With a 75Ω coax installation, 50' should be no problem. If it doesn't work, try a heavier cable with less attenuation. If it still doesn't work, you might want to fiddle with the input circuit on the DAC. If all else fails you could build your own Rx & Tx modules and use whatever cable is appropriate.

I now return you to your normal disinformation.
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Old 14th February 2004, 01:01 PM   #7
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Quote:
Originally posted by jwb
People, please. Think! before you write your post. Absolutely nobody uses a repeater for a computer network of only 50-70 feet. A category 5 cable installation has horizontal runs up to 295 feet and operates at 100MHz. A category 6 installation tops 250MHz at the same distance. And this is all with UTP.

I wasn't talking about a copper connection. I know the distances of an UTP. I was talking in general if the cable run gets too long. If have no idea how long a toslink or coax may be in a hifi installation. So if a cable gets too long they use a repeater that is what I was refering to.

...
and please share the reasons why toslink is inferior to coax.
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Old 14th February 2004, 01:43 PM   #8
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Quote:
and please share the reasons why toslink is inferior to coax
For one thing, there's two additional devices that have a high potential for added jitter (refering to the extra buffers/drivers within the toslink receivers and transmitters)

For another thing, the toslink cable standard sucks. The plastic used for this is about the lowest grade possible for optical transmissions. Slight bends cause all sorts of stress on the plastic that act as reflectors which then induce jitter or noise.

For another thing, the actual connectors are incredibly loose and prone to damaging the surface of the fiber at the jack... which again causes signal degredation or noise.

The various options for 75ohm coax are so plentiful in terms of very good cables, that that alone outweighs using a POS toslink.

The noise levels that are emitted from a coax cable running an SP-DIF are so ridiculously low, that there's no point in mentioning transmissions onto other cables (assuming you have a descent coax cable)

With a pseudo-good driver, coax can run long lengths without a problem if using a good quality, low loss cable.

I'm sure there are more items on the table, but I need to run off...
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Old 19th June 2004, 01:50 AM   #9
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TV/Radio Antenna-Cable (75 Ohm) works up to 100m (300feet?) very fine !

Regards
Jobstens
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Old 19th June 2004, 09:16 AM   #10
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For another thing, the toslink cable standard sucks. The plastic used for this is about the lowest grade possible for optical transmissions. Slight bends cause all sorts of stress on the plastic that act as reflectors which then induce jitter or noise.
Hi, i do not think that this is necessarily true. Here is a link where I have measured jitter in 60m long fibre bundle consisting of around 95 (IIRC) 20cm diameter turns. Results are not significantly worse than in previous measurement with short fibre. I think that it is the receiver and transmitter part that is the weakest link in POF communication. After all, 200MHz POF links are available, and I think that 2GHz communication over POF has been demonstrated.

Best regards,

Jaka Racman
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