Does optical audio cable brand matter for a 50ft run? - AVS Forum
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post #1 of 10 Old 09-15-2013, 09:47 AM - Thread Starter
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I have a home theatre setup with my Yamaha HTR-6130 and I'm looking into getting a long optical audio cable to connect my PC since the AVR doesn't decode HDMI audio. I'm guessing cable brand doesn't matter much for shorter runs, but would it make a difference for a 50ft run?
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post #2 of 10 Old 09-15-2013, 10:18 AM
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I think you would be better off using coax, not optical, for a 50' run. There are converters. Most plastic optical cables aren't up to handling that length. You might be able to do it with a glass one, but you will pay more. It is going to depend on the transmitter and receiver. They weren't designed with that kind of distance in mind.
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post #3 of 10 Old 09-15-2013, 11:19 AM - Thread Starter
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Thanks for the reply. And oh, would coax be better? The loss of quality in the conversion wouldn't be worse than just using a long optical cable? I also saw on this sticky that optical is better than coax for longer runs but the person didn't say why.

Either way, coax might be better because the optical cable would have to be bent a bit, but I'm wondering if converting the signal and using coax into the receiver would make it worse, since looking into getter a new AVR that supports HDMI audio is also an option (although not an ideal one).

Also not sure of the subtleties of how 5.1 even works, but from the sound of it, both coax and optical will only output 5.1 if the source is encoded in that Dolby format? So basically most new movies and games, but nothing else?
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post #4 of 10 Old 09-15-2013, 11:44 AM
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Quote:
Originally Posted by _eternal View Post

Either way, coax might be better because the optical cable would have to be bent a bit, but I'm wondering if converting the signal and using coax into the receiver would make it worse, since looking into getter a new AVR that supports HDMI audio is also an option (although not an ideal one).

It's a digital signal. If the conversion affected it in any way, it'd be a complete dropout of sound, not a gradual degradation. Converting shouldn't affect if if the converter box is working properly.
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Also not sure of the subtleties of how 5.1 even works, but from the sound of it, both coax and optical will only output 5.1 if the source is encoded in that Dolby format? So basically most new movies and games, but nothing else?

5.1 soundtracks have been around since the mid-90s, first appearing for the home on laserdisc. It's since migrated to DVD, Blu-ray, games, broadcast TV, cable TV, sat TV, and internet streaming. It's hard not finding a movie, game or HD TV show that doesn't have 5.1 or better. It's not just Dolby, either. DTS (Digital Theater Sound) is another company with 5.1 and better soundtracks (better being 6.1 DTS-ES and 7.1 DTS-HD codecs.)

If the source isn't encoded in 5.1, your receiver can matrix a stereo source out to 5.1, with varying results.

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post #5 of 10 Old 09-15-2013, 12:07 PM - Thread Starter
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Ah, thanks. I'll go for the coax solution then. Do you all have any recommendations for optical to coax converters? I'm seeing mixed reviews on amazon for a bunch; some claim there's static or that it only passes stereo, not 5.1.
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post #6 of 10 Old 09-15-2013, 12:13 PM
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This one should work:http://www.monoprice.com/products/product.asp?c_id=104&cp_id=10423&cs_id=1042302&p_id=2948&seq=1&format=2

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post #7 of 10 Old 09-16-2013, 10:36 AM
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Quote:
Originally Posted by _eternal View Post

I also saw on sticky that optical is better than coax for longer runs but the person didn't say why.
There are a lot of errors in that page. The author obviously doesn't know much about the topic.
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post #8 of 10 Old 09-16-2013, 11:01 AM
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Quote:
Originally Posted by _eternal View Post

Ah, thanks. I'll go for the coax solution then. Do you all have any recommendations for optical to coax converters? I'm seeing mixed reviews on amazon for a bunch; some claim there's static or that it only passes stereo, not 5.1.

Claims that a digital link component of that kind adds static or only passes stereo are pretty incredible. A digital link can't add static (noise), that is the nature of a digital link. Stereo and multichannel data streams are essentially identical at the coax/optical level. They are both bitstreams composed of packets and you can't distinguish stereo packets from multichannel packets without decoding the bits inside of the packets, which a optical to coax converter has no need or purpose in doing.

If you send 5.1 packets to a DAC that doesn't know about multichannel it will output random noise because that what multichannel packets look like to a stereo converter. That is a very basic configuration problem, nothing that a coax to optical converter can help or cause all by itself.

The rule of thumb and my experience is that coax is superior to optical for very long runs. Optical cable used to be limited to 10 meter runs, but that limit has been raised in some cases by new technology in the equipment and the cable.. I've run coax for far longer runs that that.

The downside to coax is that it makes a metallic connection between the devices at both ends which optical does not. The metallic connection can lead to ground loops and hum.
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post #9 of 10 Old 09-16-2013, 11:05 AM
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"Optical is better" when stated by an audio magazine reviewer comes mostly form the layman's idea that fiber is superior to copper for long runs. I think that gets extrapolated from the IT industry where this claim is quite true. After all, internet and long distance telephone as well as video links are fiber optic these days.

But that is not the same stuff as SPDIF fiber cable. SPDIF optical cable is plastic and uses visible light modulation where as true communications fiber optics is very high quality glass fiber and laser modulated. Quite a difference in performance.

In the SPDIF world fiber is inferior to copper with exception to ground loop isolation. But as many other devices are also interconnected in the system with copper wire, it's basically irrelevant.

For a 50 foot SPDIF copper cable just use standard 75ohm video cable. RG59 is fine, you don't need RG6.

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post #10 of 10 Old 09-16-2013, 11:07 AM
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Quote:
Originally Posted by arnyk View Post

Quote:
Originally Posted by _eternal View Post

Ah, thanks. I'll go for the coax solution then. Do you all have any recommendations for optical to coax converters? I'm seeing mixed reviews on amazon for a bunch; some claim there's static or that it only passes stereo, not 5.1.

Claims that a digital link component of that kind adds static or only passes stereo are pretty incredible. A digital link can't add static (noise), that is the nature of a digital link. Stereo and multichannel data streams are essentially identical at the coax/optical level. They are both bitstreams composed of packets and you can't distinguish stereo packets from multichannel packets without decoding the bits inside of the packets, which a optical to coax converter has no need or purpose in doing.

If you send 5.1 packets to a DAC that doesn't know about multichannel it will output random noise because that what multichannel packets look like to a stereo converter. That is a very basic configuration problem, nothing that a coax to optical converter can help or cause all by itself.

The rule of thumb and my experience is that coax is superior to optical for very long runs. Optical cable used to be limited to 10 meter runs, but that limit has been raised in some cases by new technology in the equipment and the cable.. I've run coax for far longer runs that that.

The downside to coax is that it makes a metallic connection between the devices at both ends which optical does not. The metallic connection can lead to ground loops and hum.

BTW the reason why optical used to be limited to 10 meters was loss over the low tech piece of plastic that is used in most consumer optical links. High end professional optical links use special glass fiber and vastly different connectors which have lower loss, but cost a lot.

Coax has loss too, but the way things are usually done, the losses usually don't become harmful until the links are many times longer (100s of feet).
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