Chromecast Audio Connection Question

Discussion in 'Digital Integration' started by iramegdal, Dec 23, 2017.

  1. iramegdal

    iramegdal Well-Known Member

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    I am very happy with streaming Chromecast Audio from my PC or handheld device. I have 2 of them, and just bought a third. I run each of them through Emotiva DACs. When I purchased the third, the store had no mini-plug to toslink cables. So I ordered an Amazon basic version. It is considerably thinner than the other 2. Will that matter for this kind of cable?
     

     

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  2. Wildcat

    Wildcat Audio Sommelier

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    4,535
    Should be fine. I've rarely used optical cables, but I had one so thin that I seriously doubted it would work...and it worked fine. (It was bundled in with a component I bought many years ago.)

    I am ordering a cable from Amazon myself for the same reason--going to use one of them with a DAC.
     
  3. robert_kc

    robert_kc AK Subscriber Subscriber

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  4. Wildcat

    Wildcat Audio Sommelier

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  5. E.Auer

    E.Auer Super Member

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  6. iramegdal

    iramegdal Well-Known Member

    Messages:
    520
    Location:
    Cherry Hill, NJ

     

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  7. Poultrygeist

    Poultrygeist Lunatic Member

    Optical cables either work and pass the signal or they don't work and don't pass the signal. There are no degrees of how well they work so buying cheap can make sense.
     
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  8. iramegdal

    iramegdal Well-Known Member

    Messages:
    520
    Location:
    Cherry Hill, NJ
    Is the same true for coaxial digital cable? I use a 7 ft. cable from CD player to Emotiva DAC/receiver, but could use a shorter one. Does it matter?
     
  9. Poultrygeist

    Poultrygeist Lunatic Member

    Same for all digital cables. Length would be a matter of convenience.
     
  10. gvl

    gvl Well-Known Member

    Messages:
    987
    Experts disagree: https://positive-feedback.com/Issue14/spdif.htm , however it may be less of an issue for DACs with ASRC such as Emotiva DC-1.
     
  11. Poultrygeist

    Poultrygeist Lunatic Member

    Longer cables are more convenient as irmegdal already has a pair. :)
     

     

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  12. cpt_paranoia

    cpt_paranoia Active Member

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    That's not quite true...

    Digital cables (optical or coax) carry the digital information using an analogue physical representation; the intensity of light, or a voltage on a wire.

    Both of these representations can be degraded by transmission down their cables.

    Cheap optical fibres are plastic, and the attenuation per metre isn't trivial. Since they're not monomode optical fibres (as used for long-distance, high-speed optical data comms), the pulses will also smear. Make that cable long enough, and the receiver will eventually be unable to recover the data at the other end.

    Similarly, for coax cables, a poor cable will cause losses and reflections due to impedance mismatches, both of which will degrade the signal, and eventually cause problems for the data recovery at the receiver.

    Even if no data errors occur, poor signal integrity will increase the jitter in the recovered clock.

    That said, for the short distances usually involved in connecting optical or coax SPDIF sources to SPDIF DACs, rather too much fuss is made about the quality of cables... You certainly don't need gold-plated connectors on your optical fibre cable (as I have seen suggested...), and I'm quite happy using 1m optical cables bought for £1.
     
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  13. Poultrygeist

    Poultrygeist Lunatic Member

    If the digital cable works it works and the only other option is it doesn't work. If you spend lots of money on digital cables it helps to think otherwise.
     
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  14. cpt_paranoia

    cpt_paranoia Active Member

    Messages:
    337
    The point I am trying to make is that 'working' is not a binary parameter.

    You may get an audio signal, without any bit errors, but the sound quality may be degraded, depending on the nature of the interface; I mentioned SPDIF specifically, because that interface does not support DAC-controlled sample clocking (such as is used in the 'asynchronous' USB audio data streams), so the sample clocking must be related to the clock recovered from the biphase-encoded SPDIF stream. This recovered clock can have more jitter than a free-running xtal oscillator that might be used in a system where the DAC is master of the interface timing (data pulled from source by DAC, rather than pushed by source to DAC). This is discussed briefly in the Wiki entry on SPDIF:

    https://en.wikipedia.org/wiki/S/PDIF#Limitations

    Don't get me wrong; I'm very sceptical of many of the claims made by people about some of the things that are supposed to affect sound quality (e.g. the gold-plated SPDIF connectors, the need to keep your media on an HDD, not an SSD (unless you have a magic pixie dust filter on the SSD PSU)). But I can see a genuine physical mechanism by which a poor SPDIF signal could influence sound quality (imaging, specifically), by introducing jitter on the DAC sample clock.

    Your point about the money spent on expensive cables (etc) is, I assume, alluding to confirmation bias; people convince themselves that their expensive pixie dust filter and unicorn mane interconnects are improving their sound. Double blind testing is required.

    I don't spend a lot of money on interconnect cables.
     
  15. gvl

    gvl Well-Known Member

    Messages:
    987
    Folks here tend to favor the idea that jitter was invented by marketing and that all cheapo DACs are immune to jitter because it doesn't exist.
     
    Last edited: Jan 23, 2018
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  16. cpt_paranoia

    cpt_paranoia Active Member

    Messages:
    337
    I come from a background of designing synthesized frequency sources and digital RF modulators, where jitter is called phase noise, and has a definite effect... I started my career, 30 years ago, by designing and implementing the GMSK modulator (using direct digital synthesis) for Vodafone's initial GSM handsets and base stations.

    I've also worked on digital modems, and have an understanding of signal degradation, and the effect on eye patterns, and clock and data recovery (aerosatcom). This, and VoIP systems also mean I have an understanding of plesisochronous data systems, and the various ways to cope with the frequency mismatch between the two ends.

    I'm not convinced that my ears are up to hearing the effect of jitter, but I can see a mechanism by which it might influence the sound, that other people might be able to distinguish.
     
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  17. gvl

    gvl Well-Known Member

    Messages:
    987
    I reported on another thread a very noticeable improvement from placing a SPDIF reclocker between my CCA and the DAC, I'm more than 100% sure it is not in my head as the difference is pretty obvious. If this is not due to jitter I don't know why. There exist jitter eliminating solutions on SPDIF inputs, so it is not limited just to the USB. However I'd spend every reasonable effort (this doesn't include spending 3-digits on cables) on making sure my digital interconnects and/or sources don't introduce jitter if my DAC didn't have any of those solutions on-board.
     

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