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Optical cable quality??

Discussion in 'Cables & Switches' started by ManGina, Mar 23, 2005.

  1. ManGina

    ManGina
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    Does anyone agree there is a big difference in the quality of an optical cable? The prices seem to vary from £4 upwards for 1m. Will I get much better sound from a cable costing £25, or is this an area where the laws of diminshing returns reign king?
    I know there have been similar questions for HDMI cables and arguments that there will be no loss of digital signal at such short distances - but :confused:
    Has anyone upgraded or conducted a test which confirms "you get what you pay for" :lease:

    Apologies if this has been discussed elsewhere. I have searched but to no avail. Thanks everyone.
     
  2. eviljohn2

    eviljohn2
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    There is a difference between some optical fibres but it will only be apparent if you're sending signals hundreds of metres or more. :)
     
  3. Brash

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    Being digital it's either on or off (duh!!). Basically, the signal will either be seen by the amp or not. If it's not the amp will ask for the data to be resent and in the mean time will use an in built buffer. For short lengths basic optical cable is fine. As for gold plated terminals on optical cables..... :suicide:
     
  4. eviljohn2

    eviljohn2
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    Just to add, the cable quality won't vary much but the quality of the terminations will so make sure the build quality on them is up to a good standard. :)
     
  5. Kevo

    Kevo
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    Instead of 1 0 1 0 1 etc you could end up with 0.9 0 0.8 0 0.9 0 etc on inferior or longer 'digital cables' ;)
     
  6. ManGina

    ManGina
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    Yes thanks Brash (apt) I'm well aware it's on or off but you obviously haven't read similar threads on HDMI cable quality.
    As eviljohn2 indicates termination quality is an issue and you think the idea of gold plated terminals make you want to kill yourself, it's obviously not clear cut.
    Sorry kevo, I don't see how it could be 0 0.9 etc, surely its either 0 1 0 1 or 0 1 0 1
     
  7. eviljohn2

    eviljohn2
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    Gold plated connectors aren't too relevant in optical situations but a good quality lens is.

    The 0 1 0 1 in a digital signal isn't quite as simple as that. Consider that digital 0 means that the voltage delivered should be zero and that digital 1 means that the voltage delivered will be +5V (the outright values aren't relevant to us here but they help provide an insight. I'm using TTL in this example).

    The reality is that a signal doesn't have to be that exact voltage for the logic circuit to operate as if it saw digital 1 or digital 0. For example, any voltage between about 3V and 7V will be considered to be digital 1 by the logic circuit and there is a similar bandwidth for digital zero. The circuit that responds to this signal will operate in exactly the same way as long as the voltages fall within the specified digital bands. This means that any noise or attenuation along the signal carrier makes no difference to how the circuits operate and similarly it means that a single 5V output can feed several inputs even with the voltage being inherently lowered.

    There is some good information including illustrative diagrams here:
    http://www.allaboutcircuits.com/vol_4/chpt_3/11.html
     
  8. Knightshade

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    I personally can't tell the difference. I can tell the difference between coax and Optical but not different types (quality) of optical. It makes sense though that a well finished cable should be better. Whether that makes a difference audibly? That's the question really.
    Something else to consider is the quality of the torx connector at each end. No point having a nice glass cable and then plugging it into a cheap and cheerful connector. probably forgotten by most....
     
  9. hb1966

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    I thought the link between an amp and a source was a continuous bit-stream? I didnt think the amp was able to request a resend. Errors are usually handled with Forward Error Correction.
     
  10. caleb

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    IMHO, the sound quality of optical is inferior to digital coax.

    Also the quality of the actual optical cable is not as much of an issue as the quality of the connector going into the source and processor - if it can't keep the optical cable in the right orientation then it's not good.
     
  11. Nick_UK

    Nick_UK
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    There are two schools of thought.....

    Optical is supposed to be susceptable to "clock jitter" which theoretically can interfere with decoding and introduce errors. That makes co-axial look like a more attractive proposition. However, a co-axial connection allows an electrical path between the chassis of components, and poor earthing can introduce problems in the D/A conversion chips, which can also introduce errors.

    So, basically, it's six of one, and half-dozen of the other :)
     

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