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Toslink and Coax spdif

Kw6

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Hey everyone!

I want to use one metre of Toslink or coax. Is it a myth which says the minimum length of these cables should be at least1.5 metres so there won't be any cable reflections?

Thanks!
 
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Kw6

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Ok thanks! I will just get 1 metre!
 

threni

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antcollinet

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Don't forget that if you use Toslink, the fibre has to have a diamond core. Else the quantum pixies steal all the bits. Or something.

:p
 
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Kw6

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But the guy in the shop said to get 10 metres, just to make sure. And a spare amp!
Haha! Btw is there any audible differences in audio applications for glass fiber bundles vs one plastic core or even multiple plastic cores?
 

antcollinet

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Haha! Btw is there any audible differences in audio applications for glass fiber bundles vs one plastic core or even multiple plastic cores?
No - at least not subtle ones. If the data gets through intact, it will be perfect.If it doesn't, the result is gross problems - pops, clicks, dropouts. There are no "subtle changes" resulting from corrupted digital signals.
 
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Kw6

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No - at least not subtle ones. If the data gets through intact, it will be perfect.If it doesn't, the result is gross problems - pops, clicks, dropouts. There are no "subtle changes" resulting from corrupted digital signals.
Ok appreciate your explanation Tony!
 

pseudoid

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Hey everyone!

I want to use one metre of Toslink or coax. Is it a myth which says the minimum length of these cables should be at least1.5 metres so there won't be any cable reflections?

Thanks!
It is a myth.
But not a 100% myth, as "reflections" are always a part of the cable and connectors copper or fiber.
It really is the amount of that reflection that really matters, in the physics of things...
VSWR? anyone?
 

antcollinet

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But not a 100% myth, as "reflections" are always a part of the cable and connectors copper or fiber.
It really is the amount of that reflection that really matters, in the physics of things...
VSWR? anyone?
I don't think that is the type of reflection referenced in the question.

That article is talking about the reflections at the "wall" of the fibre, effectively guiding the light beam down the fibre.

Reflections relevant to cable lenths (and in copper wires), are those that result from impedence mismatches typically where the cable or fibre is terminated at a connector and results in reflections from one end of the cable back in the opposite direction.
 

antcollinet

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I used to believe that, until I encountered this:
clean
dirty
Well let's put to one side the fact I can't hear any difference between those two clips :), what sort of digital corruption are they supposed to relate to?

Perhaps you should also link to the description of what they are presenting.
 

Chrispy

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Hey everyone!

I want to use one metre of Toslink or coax. Is it a myth which says the minimum length of these cables should be at least1.5 metres so there won't be any cable reflections?

Thanks!
Hadn't even heard of that particular nonsense....
 

MRC01

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Well let's put to one side the fact I can't hear any difference between those two clips :), what sort of digital corruption are they supposed to relate to?
Perhaps you should also link to the description of what they are presenting.
The one marked "dirty" has digital glitches caused by a clock mis-match and buffering problem between source & target. Listen for a subtle "grit" or "grain" that taints the purity of the oboe's tone quality.
 

antcollinet

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The one marked "dirty" has digital glitches caused by a clock mis-match and buffering problem between source & target. Listen for a subtle "grit" or "grain" that taints the purity of the oboe's tone quality.
Ok - listening with earbuds and at higher volume (Mrs TC is in bed). Yes - but it is quite noticeable. A little like surface noise/crackles on vinyl, if I'm hearing what you are. But it is not the sort of subtle change (eg to sound stage or frequency response, or "lifting of veils") often attributed by audiophiles to different "high end" digital cable. In fact clock mismatch is not the sort of problem that can be impacted by cable quality in any case - I think - as long as bit edges can be detected at all.

If clock mismatch, and buffer overun or underrun - then I'm guessing at very narrow drop outs. (complete missing samples). This is going to be harder to detect than corrupted samples (bit flips - where it is just as likely for huge changes in a sample value as it is for small changes) which result in pops/clicks.
 

MRC01

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Well let's put to one side the fact I can't hear any difference between those two clips :),
...
Ok - listening with earbuds and at higher volume (Mrs TC is in bed). Yes - but it is quite noticeable. A little like surface noise/crackles on vinyl, if I'm hearing what you are. But it is not the sort of subtle change (eg to sound stage or frequency response, or "lifting of veils") often attributed by audiophiles to different "high end" digital cable.
Yep, that's it. If you didn't hear any difference the first time around, I'd say that's a good working definition of "subtle".

This timing/buffering is inherent to SPDIF interfaces, because data delivery is controlled by the upstream device, so the downstream device has to adapt to it. Normally, it works seamlessly. But sometimes, as these clips demonstrate, it doesn't. And when it doesn't, it's not necessarily obvious.
 

jasonhanjk

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Just use 44.1kHz or 48kHz and you'll be fine.
Anything more than 48k and unlikely to get that additional 0.0001% THD improvement.
 
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antcollinet

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Yep, that's it. If you didn't hear any difference the first time around, I'd say that's a good working definition of "subtle".

This timing/buffering is inherent to SPDIF interfaces, because data delivery is controlled by the upstream device, so the downstream device has to adapt to it. Normally, it works seamlessly. But sometimes, as these clips demonstrate, it doesn't. And when it doesn't, it's not necessarily obvious.
I was listening with speakers, and at a volume at which the distortion was below hearing level in my room (with PC fans running). At a volume where it can be heard - it is not that subtle. It actually sounds like a crackle. By sutble (at least in my mind) I didn't mean low amplitude/volume. I was using subtle to describe the sort of audio quality impacts that some audiophiles ascribe to high end cables, as mentioned above.

I'm aware of clock recovery in SPDIF - But I am not clear on the causes for it to go so catagorically wrong as to cause buffer overruns/underruns. Expecially as the data is being detected (Since the music actually gets through) so the bit edges that the clock recovery should work from are there. Unless there is a bug in the DAC causing the PLL to lose lock - or the jitter is so severe that it can't lock on in the first place - but that would suggest a poorly designed dac.
 

jschwender

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I have seen many poorly designed sound cards where the SPDIF interface is only hooked up without proper synchronisation. They fix it by just re-sampling – unbelievable but true.
 
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