Tellurium Q Black Digital Cable

Discussion in 'General Electronics Chat' started by seasusa, Apr 29, 2016.

  1. seasusa

    Thread Starter New Member

    Apr 29, 2016
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    Hi,

    I bought this £400 Spdif coaxial cable for my audio system. While checking for any shorts in the cable I picked up a 10K Ohm resistance in the cable. Curious to find out I took the blue putty off the connect to find a 10K resistor connected between the ground and signal conductor. This is the first coax cable I have come across with a resistor inside. I am wondering what could be the technical reason for this, and could it cause damage to the equipment? I have attached a picture for everyone to look at.

    [​IMG]
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    It will not damage any equipment. I believe that SPDIF uses a differential driver and receiver. In some equipment this is actually an RS-485 device. If there is no driving source you want the potential levels on the two inputs to be equal and discharge the distributed capacitance of the cable. Normally this 10kΩ impedance would be in parallel with a smaller termination resistance at the receiver. Does this cable only have one resistor or does it have one at each end?

    http://cds.linear.com/docs/en/datasheet/485fk.pdf

    PS: I know for a fact that the Wadia 121 DAC uses RS-485 transceivers for the SPDIF inputs.

    PPS: I'm even more impressed that you paid that much for a cable and then hacked it!
     
    Last edited: Apr 29, 2016
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  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    You paid what?
     
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  4. crutschow

    Expert

    Mar 14, 2008
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    I'm double impressed that someone would pay £400 for a digital audio cable where a standard £10 cable would give the same results. :rolleyes:
    Ranks right up there with £500 power cords.
     
  5. seasusa

    Thread Starter New Member

    Apr 29, 2016
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    Thanks for answering my question. So to answer your question the 10K resistor is on the receiver end, and I don't see any on the source end.

    So after looking around I came upon a video link below. Where it explains why you would terminate a Coax cable with resistance. Apparently it has something to do with not allowing reflections to get back into the cable from the receiver end. And the termination resistance matching the characteristic impedance of the cable.

    As being discussed in this video:
    https://www.youtube.com/watch?time_continue=4&v=zrDxSM91Jcg
     
  6. crutschow

    Expert

    Mar 14, 2008
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    But 10k is way too high to be a termination resistance.
    Such a resistance is usually in the neighborhood of 50 to 75 ohms for coaxial cable (the characteristic impedance of the cable).
     
  7. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Just return it and buy a $10 one..
    You got massively ripped off..
     
  8. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    EEVblog #29

    But, but, but its special, per their site.
     
    Last edited: Apr 29, 2016
  9. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Sounds like the "Monster" kind of stuff to me too.

    BTW, you might ask whether the cables contain any tellurium. That is, before you return them. Most tellurium is radioactive:
    The main use of tellurium with which I am familiar is an alloy of copper to make it more machinable.

    John
     
    Last edited: Apr 29, 2016
  10. OBW0549

    Well-Known Member

    Mar 2, 2015
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    Heck, he got off easy! These folks will sock you £400 just for a USB cable. Or £2292 for a set of XLR cables. And they don't even appear to pre-condition their cables like these people do.

    Their explanation of why they don't publish any technical specs for their cables is... illuminating.
     
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  11. seasusa

    Thread Starter New Member

    Apr 29, 2016
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    You do have a point, 10K resistor is too high. The cable seems to be working fine but yesterday after about 6 hours of use my DAC/Amp had a slight burning smell coming off it :).
     
  12. nsaspook

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    Aug 27, 2009
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    Even respected component manufacturers need to cater to the 'audio' clients. It's just good business and 'it has to be done' to sell.
     
  13. jpanhalt

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    By "cater" to the clients do you mean "pander" to their ignorance?

    John
     
  14. seasusa

    Thread Starter New Member

    Apr 29, 2016
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    Ok let me explain the cable retail price is around £400. I bought it off Ebay for about £150. So as it came off Ebay I tested the cable for continuity and short with my basic multimeter. While measuring for shorts I picked up a 10K resistance. Puzzled by it I unscrewed the plugs, took the blue putty off and there in front of me was a sight of 10K resistor.
     
  15. recklessrog

    Member

    May 23, 2013
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    The Panasonic article is "ENLIGHTENING" Oh dear :(
     
  16. nsaspook

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    Hypothetically, if someone requests a 'product' with those types of specifications you can't pander to them with technical brilliance.
     
  17. recklessrog

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    More like "taking advantage of their ignorance"
     
  18. nsaspook

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    Snake Oil is expensive to make and purify to SEMI grade Alpha-Omega purity.
     
    Last edited: Apr 29, 2016
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  19. seasusa

    Thread Starter New Member

    Apr 29, 2016
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    Papabravo my other coax cable from Chord does not have any resistor between the ground and signal and has been working fine. I understand your point about keeping the potential the same at both ends then why don't we see this as a common design feature in all coax cables? The only difference between the Chord and Tellurium is that one has a plastic outer plug and the other has metallic ones.
     
    Last edited: Apr 29, 2016
  20. GopherT

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    Nov 23, 2012
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    Try with the old cable to see if smell comes - if not, try the new cable to see if smell returns. If it does, feel the length if the cable looking for hot spots (unlikely with a 10k resistor). Confirm smell is coming from specific component.
     
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