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Old 5th August 2013, 02:59 PM   #11
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unbelievable sound... for the right system
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Old 5th August 2013, 03:21 PM   #12
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Hi,sorry but yes I’m sure and yes you can observe the speed a signal travels down a wire, ie with what modulation and frequency using the eye pattern method, and observe how cleanly it does so. Jitter only becomes a problem in a digital signal path once the bits can no longer be recovered at the opposite end, but within cable/interface specification this is no problem. In a digital context, BER (Bit error rate) is a much more relevant metric.
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Old 5th August 2013, 03:40 PM   #13
marce is offline marce  United Kingdom
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What a load of rubbish, gold or silver conductors will not make any difference to digital signal transmission. S/PDIF is that fast, providing the correct driver IC's are used, ie ones without silly rise times.
Skin effect and signal speed problems aint ever gonna be a problem again at the speed S?PDIF runs at, and skin effect in cables is not to much of a problem, on PCB traces where you have rectangular shaped conductors a ground plane localy etc then you may get some problems in the higher frequency stuff, but not what your average Audio DIYer is gonna ever see.;
Eye diagrams take jitter into account, you use them to get an overall view of the signal transmission.
How fast does a digital signal travel down a cable, and what causes the speed to be below that of light? The metal the conductor is made of has nothing to do with it what so ever. Speed for SPDIF signals isn't again going to be a problem, they are just to slow.

Basically you are just sprouting Audiophile digital myths and hand waving as I believe the expression is, go read Dr Eric Bogatin, Dr Howard Johnson, Ralph Morrison etc then you may get some understanding of digital signal transmission. Oh and electrons in any conducting metal only travel at about 0.1mm per second if that.
So for digital signals silver wire will not make the signal travel faster or provide any real benefits, MYTH...
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Old 5th August 2013, 03:49 PM   #14
Calvin is offline Calvin  Germany
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Hi,

does the cable behave like a transmissioline anyway?
Freqs as high as 25MHz mean 10-12m wavelength.
And even 1/2 or 1/4 of that is longer than the typical interconnect.
The cable should then behave like a lumped impedance.

But of course silver or gold makes an even bigger difference, if the digital signal is also buffered in memories and reclocked. Ohhh yessss

jauu
Calvin
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Old 5th August 2013, 04:00 PM   #15
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IIRC, Jocko had strong TDR words to say about correctness of drive/termination impedences and cable length/propagation velocity.
Wrong impedence matching/cable lengths can cause reflections to arrive at precisely the wrong times.

Dan.

Last edited by Max Headroom; 5th August 2013 at 04:13 PM.
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Old 5th August 2013, 04:03 PM   #16
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What's of interest here is the rise / fall time of the signal. If you know that you know the highest frequency of interest (can be much higher than 25MHz).

The rest is just basic transmission line theory... As pointed out here already, try googling "signal integrity" for more info on the subject.
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Old 5th August 2013, 04:14 PM   #17
gk7 is offline gk7
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Any cable sold for composite video (75 Ohm, yellow RCA connectors) is sufficient for S/PDIF.
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Old 5th August 2013, 04:16 PM   #18
marce is offline marce  United Kingdom
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It is the signal rise time that determines whether a signal is high speed, whether the cable should be treated as a transmission line, and when and where the reflections if any will arrive back at the driver.
If your drive strength, Tr (rise time of the signal) and impedances are all matched you shouldn't get any reflections...At the end of the day reflections are caused by too much energy being fed into the line, for whatever reasons, that cane be absorbed by the far end. Impedance mismatches down a line will also cause reflections.
But as said with a reasonable cable with SPDIF you should have no problems, sub nano second rise times will also help.
Without high speed simulation software to determine what is going on and modelling the cable and all the interfaces, you can only approximate what is happening (you need the IBIS data for the transmitter and receiver devices as well).
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Old 5th August 2013, 04:20 PM   #19
marce is offline marce  United Kingdom
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The master:
Signal Consulting, Inc. - Dr. Howard Johnson
And another:
beTheSignal.com
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Old 5th August 2013, 04:22 PM   #20
marce is offline marce  United Kingdom
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As Mark as pointed out and I have mentioned the rise time (and fall time) are the determining factors for spectral content of digital signals, look up Knee frequency:
Fknee=1/Squ Rt Tr
1 over the square root of the rise time.....
Again though without SIV software and 3D field solvers etc you can only approximate or guess.

And just in case, using silver as the conductor does not make the signal travel faster than it does in a copper conductor, which I believe was what was being hinted at with the mention of silver conductors.

Some notes on skin effect (and ground effect) just to add a bit of icing to the discussion...
http://www.ultracad.com/articles/skin%20effect.pdf

Last edited by marce; 5th August 2013 at 04:36 PM.
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