Glass TOSlink?

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by Kattefjaes, Feb 10, 2017.

  1. Kattefjaes

    Kattefjaes Mostly Harmless

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    OK, this is really basic stuff.. but if I want to know the answer, maybe other people do too.

    I am aware that conventional orthodoxy is that only glass optical connects are worth bothering with. I recall acrylic and similar being frowned upon. I remember @baldr being pretty trenchant about it, which is a good indicator.

    I do remember the polishing of the ends of the cheap acrylic connects being shoddy and causing most of the problems- however, around Them Interwebs, I've seen people asserting that this has improved. Truth or bullshit?

    Has anyone (@atomicbob maybe?) measured the attenuation of modern TOSlink connects of various kinds? What about the effect on measurable jitter caused by.. whatever the hell it is that happens in such things.. diffraction? Scattering?

    Essentially, I was looking around, and there are very few glass cables on sale in the UK, and those that exist seem to have a three digit price. There are a few that sometimes make vague claims to "glass" on some vendor sites, and some that mention being "acrylic glass"*- it seems that to really get one that uses borosilicate for sure, you need to spend upwards of £100.

    So, am I missing an easy source of glass cables? Is it really as critical any more? I'm really interested in good information where people have some measurements, as there's a lot of conflicting "night and day" and "blacker background" confirmation bias handwaving about in the world of connects, especially digital stuff.






    * People offering "acrylic glass" remind me of those people who say "I'm vegetarian, but I eat chicken".
     
    Last edited: Feb 10, 2017
  2. beemerphile

    beemerphile Friend

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  3. Kattefjaes

    Kattefjaes Mostly Harmless

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    Ah, yes, you're right, thanks. I think I skipped over those as they're all quite long, I'm looking for a 0.5 or 1m, ideally, for tidiness (and maybe nervosa). There's a 1m one by the same manufacturer, with scant detail:

    https://www.amazon.co.uk/Profigold-Performance-Optical-TOSLINK-Interconnect/dp/B003T61CAY/

    ..but you'll see that the manufacturer's (awful) site doesn't really make much mention of what they're made of:

    http://www.profigold.com/en-us/sound/digital-audio-interconnects

    You'd expect them to mention it there, if they're really glass, wouldn't you? It's as fishy as hell, hence asking daft questions.

    I agree, "medical grade" does seem to be the new meaningless buzzphrase.. there's even more of that when you start looking at power conditioners and cables; it's a bit daft.
     
    Last edited: Feb 10, 2017
  4. beemerphile

    beemerphile Friend

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    Well, they do have a contact link and a 1M cable. I like the glass cables to be long enough to make a lazy loop with them instead of the nice neat arrangements that you can make with metal conductors.
     
  5. Kattefjaes

    Kattefjaes Mostly Harmless

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    They do, it's true. I'll give them a poke. The sheer levels of snakeoil (and in some cases, outright lying) have made me so suspicious and jaded at this point, though- it's crazy.

    (Bets on how long before I lose patience and just buy another easy plastic cheapy?)
     
    Last edited: Feb 10, 2017
  6. beemerphile

    beemerphile Friend

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    No, but I'd rather have a glass cheapy than a plastic cheapy. Snake-oil is an indispensable part of marketing cables at all price levels.
     
  7. Kattefjaes

    Kattefjaes Mostly Harmless

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    Yeah, agreed. The thing is, I am not sure I trust those ones linked to be glass, as the description appears on Amazon but not the manufacturer's website.. so I might end up with a plastic cheapy anyway.
     
  8. Azteca

    Azteca Friend

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    I would also be curious to see measurements just for kicks. I avoid Toslink whenever possible. When I do use it, I have a Blue Jeans Cable product.
    https://www.bluejeanscable.com/store/digital-audio/index.htm


    It has worked very well for me and it really does have a big advantage in flexibility and durability. I can coil it nicely and put it with the other cables. I haven't busted out a microscope but I trust them to have properly polished the ends.
     
  9. Torq

    Torq MOT: Headphone.com

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    Four things matter when it comes to optical data connections:
    1. The quality of the polish on the ends of the fiber.
    2. The refractive index of the material involved.
    3. How well aligned your transceivers and fiber ends are.
    4. How closely you can match the numerical apertures between transceiver and fiber.
    TOSLINK is shockingly bad for #3 and you can't do anything about #4 easily (ST-type connections sometimes have some optical "goo" at the ends to address this ... "air" is never a good solution but that's all you've got with TOSLINK unless you want to get creative.

    Generally you want lots of very thin strands.

    Glass is better.

    From a how-well-does-it-work perspective, just buy from these guys (it might be a little more than you want to pay, and not necessarily be convenient, but once done you won't have to think about it again): Lifatec

    I've run that stuff through tests in the lab at hundreds of times higher bit-rates than is used in audio and it's been excellent. Even coiled down to it's minimum bend radius it performs way better than necessary and easily out specs the multi-hundred dollar nonsense from places like AudioQuest etc.
     
    Last edited: Feb 10, 2017
  10. beemerphile

    beemerphile Friend

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  11. Kattefjaes

    Kattefjaes Mostly Harmless

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    Bollocks to it, @Torq - not only is that stuff slightly more pricey, but appears not to be sold here :)

    However, that's two votes from very different angles for that brand. If I find that I need to use TOSlink rather than coax, I will seriously consider it. What's the minimum bend radius like on a 0.5m (I think they list it at 20 inch) one?

    Thanks for the replies, everyone, really appreciate it.
     
  12. Torq

    Torq MOT: Headphone.com

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    Indeed.

    And yet some cables will simply not work when you up the test to 192 KHz (optical S/PDIF is always 24-bit ... even if only sending 16-bit samples). Of course the original TOSLINK spec stopped at 96 KHz anyway, but it's gone beyond that since.

    From memory the glass ones were good down to a 2" MBR. The sheath makes it hard to go tighter (which is good).

    We coiled the shit up and I think we still got 400x the required performance before we had issues (though that was NOT using TOSLINK optical modules!)
     
  13. Kattefjaes

    Kattefjaes Mostly Harmless

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    Leaving aside the mental image caused by "the sheath makes it hard to go tighter", that sounds good, thanks. I'll try not to need one, but if I do, I'll seriously consider one of those bad boys.
     
  14. beemerphile

    beemerphile Friend

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    I called Lifatec on this by telephone and they said it is not a practical consideration because they use a high count of small diameter fibers and you will not fracture it unless you bend it so sharp that you crease the outer jacket. It is not dependent on the length of the cable.
     
  15. Kattefjaes

    Kattefjaes Mostly Harmless

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    Cheers, good of you :)
     
  16. Thad E Ginathom

    Thad E Ginathom Friend

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    That exact quote has always made me feel ok about plastic. Confession: I used Toslink a lot quite a while back, but hardly at all now.

    I did have the experience of thinking I'd broken one, as it sounded awful, but I'd only bent it to too small a radius. Noting that Bluejeans (my cable heroes! :pirate07:) prefer single plastic to bunches of glass, is there a difference in how far one can bend it?

    (Assuming the sheath hasn't made it too hard anyway of course. :oops: )
     
  17. beemerphile

    beemerphile Friend

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    Bluejeans are my cable heroes as well. They sold me every RCA interconnect in the house. The single plastic vs. many glass strands question can consume you all by itself. There are at least two reasons (or maybe one multi-faceted reason) why glass is multi-strand. The first being since fracture is a function of bend radius vs. fiber diameter, the smaller the fiber diameter the tighter one can bend it. At this point, for glass, the fiber is now too small to fill the aperture of the TOSLINK receiver and it doesn't conduct enough volume of light to operate it. So, many more parallel strands are used until both of these issues are resolved. At the ends, the individual strands can be melted into one and polished to near perfection. One technical advantage that the small glass strands will have over the larger plastic strand is that it will reliably operate in single mode vs. multi-mode. Single mode cables can operate at higher throughput and longer distances than multi mode cables. Because of the large diameter of the plastic strand, the light rays in the pulse may take either a direct route down the pipe or they may bounce along off of the fiber coating. It is kind of equivalent to multi-path in FM radio. The alternate paths cause the different groups of light rays to hit the receiver at different times. When this happens, the pulse, which is an aggregate of all of the rays, spreads out. The solution is to space the pulses wide enough to prevent overlap which would cause a loss of information.

    Therefore, multi-strand glass is OBVIOUSLY technically superior to single strand plastic with its ugly multi mode character. Well, yes, except that at the lengths and bandwidths needed for the TOSLINK spec, it doesn't matter as both are adequate for the task. So the fundamental question of seemingly ALL cable discussions remains: Does the technical difference make a sonic difference? And again, as is seemingly true for ALL cable discussions: Some say "hell yes" and others say "hell no". The wise philosopher Popeye the Sailor Man says: "Ya pays ya nickel, and ya takes ya choice."

    (And yes, I am still keeping my Lifatec cables, because I can)
     
    Last edited: Feb 10, 2017
  18. Thad E Ginathom

    Thad E Ginathom Friend

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    Fantastic, @beemerphile . Now I can feel exactly the same as before, but your explanation justifies it.

    Err... I think. But Perhaps not. But thanks anyway, and I am glad you have bonded with your cables. That must be nice for all of you. :D

    I love Archimago's tests and results. His "C" remains my USB cable to emulate!

    (seriously, thank you for the clarity of your multi-path explanation :bow: )
     
  19. mrflibble

    mrflibble Friend

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    I'm using the Fisual Hollywood TOSLink cable. I read on another forum that it was indeed a glass cable. I have the 1m cable. I think they are end of line because they only have 0.5m left:

    https://www.amazon.co.uk/gp/aw/d/B0...FMwebp_QL65&keywords=fisual+hollywood+optical

    I compared it to an Ixos medical grade plastic cable and the Hollywood sounded clearer and better defined to me. It is silly cheap, you can't go wrong.

    QED also do a glass TOSLink cable for about £100 for 1m IIRC.
     

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