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£20 digital optical or £20 digital coax ?

Discussion in 'AV Receivers & Amplifiers' started by coxy, Jan 20, 2003.

  1. coxy

    coxy
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    Which is the best connector for sony dvps715 dvd to yamaha dsp630 amplifier.
    I already have the optical connector which is 4 years old but recently read an article saying digital coax was best. Will somebody please advise.

    Thanks in anticipation!
     
  2. groundy

    groundy
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    I doubt even Yoda knows the answer to this one :D.

    There's been many heated debates in the past that tackle this issue. Do a search on previous posts and enjoy the reading.
     
  3. The Sheriff

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    you really need to try these out for yourself, everyone will have their own opinion on this subject, some preffer coax, others optical whilst others think they are the same.

    i personally prefer coax but thats just me
     
  4. Sigismund

    Sigismund
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    As I understand it a good digital coax should sound better than a similarly priced optical because the signal that it carries is "truer". An optical cable carries "light" which means the electronic signal has been changed, and then has to be changed back again in the amp. This leaves the door open to a little more possibility of a degradation of the signal.

    However, (!) that's "just" theory. Richer sounds sell both types and allow you to return all cables within 14 days of purchase, so you can try them out with your own kit and see if you can hear a difference.

    In my own experience my Tosh t.v. DD sounds better with an optical lead, whereas my Nak amp sounds infinitely better, ( well by at least 5%! ) with a coax.

    Hope this is helpful.

    Mark
     
  5. Jeff

    Jeff
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    What sounds better (if any) will depend more on the hardware the cables are connected to than the cables them selves. Your Sony for example might have less jitter through one of the spdif outputs, its not always the coax ouput that is the best. Toslink can also sometimes have the advantage if there are grounding issues. The likelyhood is that if you tried both they would sound (to you) exactly the same. I would go for the coax, more resilient.
     
  6. Silent Fly

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    :D :D :D .....(I can't stop)..... :D

    ______

    coxy,

    Try both. If you can hear a difference buy the one that sounds better. If you can't... "welcome to the real world".
     
  7. BigBird

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    Digital signals are just 0's and 1's, theres no getting round that. If it leaves as a 1, it arrives as a 1...thats it.

    Coaxial if generally prefered
    Noone can really answer why, probably more the the feel and look of the physical cable than anything else.

    :)
     
  8. Jeff

    Jeff
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    You don't think jitter affects sound quality, even PCM?
     
  9. BigBird

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    Sorry, you've lost me there

    Jitter may effect CD pickup, but not cables
     
  10. Jeff

    Jeff
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  11. juboy

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    Unless it doesn't arrive at all of course...
     
  12. rob@rar.org.uk

    rob@rar.org.uk
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    This was posted by NicolasB on anothet thread (sorry, don't know how to post a link):

    ***
    To give you brief answer, Demon, there are a couple of differences between transmitting pulses along a computer network cable and transmitting audio information.

    1) PCM data (e.g. a CD audio track) does NOT contain any error correction. (There is plenty of error correction available at the point where the data is being read off the disc, but typically none after that).

    2) The cables move around more, so a poorly made cable is more likely to suffer mechanical failiure.

    3) By far the most significant difference is the importance of jitter. The sound signal is eventually being fed to a DAC. For the purposes of this discussion a DAC can be regarded as a device which accepts a sequence of pulses at the input (a digital signal) at regular intervals and outputs a smoothly varying voltage (analogue signal) whose amplitude depends on the digital signal. Let's imagine that in between two consecutive sample values the output is supposed to change from 0.50 volts to 0.51 volts. In order for the "shape" of the output signal to be correct, 3 things have to happen. i) The correct sequence of pulses has to arrive. (If it doesn't then you have an actual bit error, but this is rare). ii) The DAC has to produce the correct voltage for a given input value. iii) The DAC has to produce this voltage at exactly the right time. If the output signal hits 0.51 volts slightly too early then the signal will be rising too fast. If it's too late it will be rising too slowly. We're talking a minimum of 44,100 samples per second, so that means even quite tiny errors in the timing of the pulses can result in noticeable levels of distortion in the output signal.

    This is what is called "jitter" and it's responsible for most of the distortion that one gets in digital audio circuitry (once you get past more basic problems such as noise and interference). This sort of effect doesn't matter in a computer network because there is no digital to analogue conversion at the end - so long as the correct pulses arrive the correct (digital) data can be extracted.

    The reason why optical connections are sometimes less effective than coaxial electrical connections has nothing at all to do with the transmission through the cable (usually - although cheap optical cables can develop microfractures) it's because the signal has to be converted from an electrical to an optical signal at one end of the cable, and then back to an electrical signal again at the other end. And the circuitry used to do this can often introduce jitter.
    ***
     
  13. BigBird

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    This is already clear. Whats being questioned is the difference between Coax and Optical, of which there is none, sound wise.

    well imho :)
     
  14. Demon

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    My 2 pence worth... and correct me if I'm wrong...

    Its a scientific fact that Jitter and Noise can be created from the cable, PCM dirrectly suffers from the Jitter, and DD/DTS is also affected, but the effect on DD/DTS from the cable is so minimal, that many almost discount it...

    Now, there are problems associated with both cables,

    COAXIAL - external interference and incorrect termination, or poor quality (Incorrect impedence, etc) can affect Jitter and Noise

    OPTICAL - The Optical Transmitter/receiver can introduce a bit of noise/jitter and also poor quality fibre/terminations can also cause the same.

    I think that in a £20 cable of each type, there is probably a fraction more chance of getting a well constructed coaxial, then there is an optical... since all cables are different, its hard to say 'blind'...

    Then there's the chance of jitter/noise being injected from your optical transmitter/reciever, so although the cables may be perfect for £20, you may still introduce a some jitter just by using the Optical.... but this will depend on your equipment....

    This all leads to the conclusion that for Normal use/equipment, the coaxial would probably cause less problems then optical...

    I've tried both back to back, and on my equipment, there is no audible difference to me, or anyone else thats heard it, but thats no guarantee it will on yours...
     
  15. Silent Fly

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    Can but not necessarly is created ;).

    I may agree if the connection is made with a 100mt mains cable that goes under a 10kW power trasformer :D.

    But with a 1mt coax cable, perfectly static (unless the CD player is in relative movement from the amp :D), even with a less than perfect phono plugs, I doubt that the cable can introduce any measurable noise (hence jitter).

    ...and if it is measurable, is it more than the jitter introduced by the DVD/CD player?

    ...and if it is more, is it audible?
     
  16. rob@rar.org.uk

    rob@rar.org.uk
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    OK, another try... This is a quote from Udo Zucker, CEO of Tag McLaren:

    "The SPDIF signal isn't a digital signal like a computer signal. It doesn't contain just 1s and 0s, it unfortunately also carries the timing. When the signal was defined people didn't know that our hearing would be extremely sensible to smallest timing errors (the jitter), otherwise they would surely have done it differently. In order to reduce jitter you need the ability to "transport" the exact timing of the signal and that needs in principle a very, very, very high bandwidth. The optical TOSLINK connection is bandwidth limited and hence introduces more jitter than a coaxial, which can in principle have an extremely high bandwidth."

    As with all these things the only way to determine whether the theory will apply in practice to your AV system is to try it. It might well be that there are weaknesses in the sonic reproduction of your system or your room's accoustics which will more than mask any difference between optical or coaxial interconnects. Best to borrow a couple of cables and listen to which one is best...

    Regards

    Rob
     
  17. Demon

    Demon
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    I agree.
     
  18. Silent Fly

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    When I was as school my teacher of electronics was used to tell me: "if you cannot measure it (directly or indirectly) it does not exists". :cool:

    I have nothing against Udo Zucker or Tag McLaren but when Mr. Zucker says: "... that needs in principle a very, very, very high bandwidth". Does he say what the value is? 1MHz? 100MHz? 5GHz? :confused:

    If he tells us the value we can buy a cable that has enough bandwidth and be all happy. But he does not tell us. Why? Or he does not know the value (hence, he cannot say what he says). Or he does want us to know the value (I wonder why). Or the value do not exists (but it does). :eek:

    Moreover: "The SPDIF signal isn't a digital signal like a computer signal. It doesn't contain just 1s and 0s, it unfortunately also carries the timing". It is a computer signal. It is asynchronous signal like the serial signal used in the cable that connects the modems to our computers. It is just used in another way because the conversion A/D.;)

    I am sure Mr Zucker is a very bright guy and Tag McLaren is a very good brand but it this case he might be not 100% right :D
     
  19. Jeff

    Jeff
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    Regular 75ohm coax and TOSlink are bandwidth limited. Thats why they couldn't be used for DVD-A.
     

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