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Gear / Technical Help => Cables => Topic started by: ellaguru on February 11, 2007, 06:24:15 PM
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hey...i found some pretty long opti cables > 20 ft. (i want to go soundcard>receiver across the room) but i wonder how good opti moves the signal over longer lengths...any advice?
chris
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not sure about optical, but what about digital coax? no problems with a 20' run.
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optical is best for shorter runs.
if you are going to run far w/one, try to get your hands on a DIP box to put between the PC and the cable.
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optical is best for shorter runs.
if you are going to run far w/one, try to get your hands on a DIP box to put between the PC and the cable.
I heard the opposite - a bit of length was a good thing (caveat: I know nothing :))
If you have links to some info please post them - need more knowledge for sure!
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where you'd hear that?
I have no links handy, but you can google it i'm sure.
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where you'd hear that?
I have no links handy, but you can google it i'm sure.
Googling "Long Run Toslink" seems to indicate that Toslink is preferred for longer runs...I've seen various figures cited...between 5-15 meters as the max...also the issue of glass vs plastic seems to make some difference.
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Coax is preferred for long runs. Optical can and will break up over anything more than 20' or so unless the line remains straight and untouched. Once you start moving it around, it will break up. Both will have jitter, but the coax signal will be more stable. I have a 60' run of 75 ohm video cable that I use and it works jitter free 99% of the time. Occasionally, it will break up enough that my reciever will need to relock to the signal, but it's rare. Go with coax or video cable.
Here's a quote from the web:
Digital Audio:
Digital Audio is the usual mode for running multichannel audio from one device to another. The consumer standard, SPDIF, is nearly universal, and is incompatible with the professional standard, AES/EBU audio. In a digital audio cable, all of the audio for a number of channels is combined, digitally encoded, in a single bitstream. This may be conveyed from device to device either in an optical (Toslink) cable, or in a coaxial cable, so home theater cables for digital audio may take either of those forms.
Coaxial digital audio cable is, very simply, 75 ohm video cable. The same considerations apply; tight impedance tolerance and good shielding are desirable characteristics. SPDIF signals in coaxial digital audio cable can be run, without trouble, for hundreds of feet.
Optical digital audio cable is an odd beast. It is commonly assumed that the optical signal is more robust, because most people are familiar with the notion of fiber optic cable being used to run signals with huge bandwidth over vast distances; if a whole bundle of phone lines can be condensed into one hair-thickness optical fiber and run loss-free for miles, then certainly Toslink ought to be able to run for similar distances--right? Well, Toslink fiber is plastic, and, unfortunately, isn't at all the same thing as glass optical fiber, and there are technical problems with using glass fiber to do the job of Toslink fiber (notably, that the aperture of Toslink fiber is enormous compared with the size of glass fiber). Problems with Toslink can appear on runs as short as fifteen feet, though high-quality plastic fiber may extend that limit out considerably. When selecting a digital audio cable for home theater, if it's possible to run coaxial rather than optical, that's usually the best option, especially if significant distance must be covered.
There is also balanced digital audio--AES/EBU audio is conventionally run balanced, though it's not uncommon to see it converted to unbalanced form for long runs, and run in video coax, because of the tighter impedance tolerance of the video cable.
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like I said...
not good for long runs.
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thanks for the advice...
chris
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:coolguy:
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like I said...
not good for long runs.
FYI:
well..i just grabbed a 30ft opti and its working fine for my set up here...
chris
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I read something about very short optical cables being a problem. Maybe that is where the post above got the idea that optical is better for long runs. The article I read said something about too short of an optical cable can cause problems because the light can bounce back through the cable causing problems. Cables over 3ft? wont have this problem. ???
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i dont know for sure but this cable seems to be just fine for my ap here.
....that + 'rubber soul' mono sounds really sweet at top volume right now ;D ;D
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i'm sure it works....
but its probably jittery.
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can you hear jitter?
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can you hear jitter?
You can if you have chili for lunch.
you can feel the jitter as well @ that point
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you can hear it when its eliminated.
(like adding a DIP to drive the long cable, or having an apogee BIG BEN in front of the DAC).