#432833 - 10/02/03 04:47 AM
SPDIF Digital Audio Routing. 75 ohm or 110 ohm?
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starlight
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Registered: 12/30/00
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Hi, everyone.
Should I use 75 ohm coaxial cable or 110 ohm digital cable for spdif digital audio?
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#432834 - 10/02/03 08:23 AM
Re: SPDIF Digital Audio Routing. 75 ohm or 110 ohm?
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Christian Peters
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Registered: 07/01/03
Posts: 29
Loc: Berlin, Germany
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Starlight,
you should definitely use 75 ohms coaxial cables for S/PDIF transfers. 110 ohms cables are used for AES/EBU connections.
Regards, Christian.
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#432835 - 10/02/03 11:37 AM
Re: SPDIF Digital Audio Routing. 75 ohm or 110 ohm?
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StoneinaPond
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Registered: 11/22/02
Posts: 2009
Loc: New York City
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Christian,
I asked a question on another thread to which you did not reply. I am quoting it here.
quote:
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Regarding your question about the line you should use for clocking, in principal I would recommend to take an AES/EBU line instead of an ADAT line. The AES/EBU line or connection should normally carry lower jitter levels.
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Christian,
I have heard a similar comment made before. Would you care to elaborate on that. What is it that makes Lightpipe more "Jittery?"
Thanks.
_________________________
Yorik
Stone In A Pond
"Man will occasionally stumble over the truth, but most of the time he will pick himself up and continue on."
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#432836 - 10/02/03 05:51 PM
Re: SPDIF Digital Audio Routing. 75 ohm or 110 ohm?
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Christian Peters
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Registered: 07/01/03
Posts: 29
Loc: Berlin, Germany
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Yorik,
at first, my statement was based on measurements we did by ourself with different S/PDIF interfaces - coaxial and optical with identical signals - using our AP System Two Cascade. Also we have a lot of experiences with ADAT interfaces where we find out same differences compared to AES/EBU sections on our mainboards.
Additionally, I had a couple of discussions with developers regarding this matter. We agreed that one of the main reasons could be the large tolerances the optical interfaces are working with when converting the signals from electrical to optical or vice versa.
A second reason could be the optical cables, especially the plastic fibre cables. We think bad refractive indexs or angels of refractions in the cable could cause an increasing signal distortion. In this case it would also be interesting to compare plastic fibre cables and glass fibre cables. Unfortunately we had no possibility to do this by ourself up to now. We assume that the transfer through glass fibre will cause less distortions due to better refraction conditions in the glass material. This could also be a reason for the much longer transfer distances which are possible with glas fibre cables instead of plastic fibre cables. But this is only our personal opinion.
Regards, Christian.
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#432837 - 10/02/03 06:20 PM
Re: SPDIF Digital Audio Routing. 75 ohm or 110 ohm?
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StoneinaPond
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Registered: 11/22/02
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Christian,
Thanks for your response.
How much variance in the jitter spec did you register?
Was it always uniform?
Are there many manufacturers of the optical interfaces, or just a few?
It would be helpfull if those could be identified when making purchase decisions, if indeed these are the culprits.
The issue of the types of cables is also interesting. I must check mine to see what kind I am using.
_________________________
Yorik
Stone In A Pond
"Man will occasionally stumble over the truth, but most of the time he will pick himself up and continue on."
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#432838 - 10/02/03 10:45 PM
Re: SPDIF Digital Audio Routing. 75 ohm or 110 ohm?
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starlight
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Registered: 12/30/00
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Originally posted by Christian Peters:
Starlight,
you should definitely use 75 ohms coaxial cables for S/PDIF transfers. 110 ohms cables are used for AES/EBU connections.
Regards, Christian.
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#432839 - 10/02/03 11:30 PM
Re: SPDIF Digital Audio Routing. 75 ohm or 110 ohm?
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Griffinator
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I have definitely seen positive audio response between the plastic fiber and glass fiber cables (at a significant impact to my wallet, but well worth it!)
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#432840 - 10/03/03 01:23 PM
Re: SPDIF Digital Audio Routing. 75 ohm or 110 ohm?
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StoneinaPond
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Registered: 11/22/02
Posts: 2009
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Scott,
I'm having problems figuring out which cables are glass as opposed to plastic.
Which manufacturer are yours and were did you get them?
Thanks.
_________________________
Yorik
Stone In A Pond
"Man will occasionally stumble over the truth, but most of the time he will pick himself up and continue on."
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#432841 - 10/05/03 09:18 AM
Re: SPDIF Digital Audio Routing. 75 ohm or 110 ohm?
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Christian Peters
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Registered: 07/01/03
Posts: 29
Loc: Berlin, Germany
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Starlight,
the differences and effects on the transfered signal are not so dramatically. When using a 110 ohm cable between a 75 ohms S/PDIF transmitter and receiver the signal will receive some more „ringing frequencies“ after the top of the rising edge and after the end of the falling edge. But the rising edge which is most important for locking the receiver will not be affected.
As I read your initial question I though you wanted to buy new cables, so I recommended 75 ohms S/PDIF cables. I did not know that you already bought some others. Sorry.
Regards, Christian.
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#432842 - 10/06/03 03:21 AM
Re: SPDIF Digital Audio Routing. 75 ohm or 110 ohm?
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starlight
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Registered: 12/30/00
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Originally posted by Christian Peters:
As I read your initial question I though you wanted to buy new cables, so I recommended 75 ohms S/PDIF cables. I did not know that you already bought some others. Sorry.
Regards, Christian.
I already got one but did want to buy new cables for another S/PDIF connection. So far I was moving the cables room to room whenever I need them(about once a month) and I got tired of doing so,,
At the time I ordered my first S/PDIF cable, I'd never used any digital connection and I had no info about word clock, AES/EBU, S/PDIF,,, . I was using an analog mixer with ADATs connected with all analog cables. And I had to change the mixer since it was getting old and I decided to get a digital mixer(d8b). The d8b dealer around here got me those 110 ohm spdif cables with other equipments that I ordered. Since it sounded normal although it sounded a lot different from analog, I did not know the cable was for ABS/EBU. I did listen to the same file through ADAT optical cable and the 110 ohm spdif cable, still I could hardly see big difference between them. Probably I could with some better sounding digital system.
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#432843 - 10/06/03 08:36 AM
Re: SPDIF Digital Audio Routing. 75 ohm or 110 ohm?
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Christian Peters
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Registered: 07/01/03
Posts: 29
Loc: Berlin, Germany
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Originally posted by starlight:
Thank you Christian.
I already got one but did want to buy new cables for another S/PDIF connection. So far I was moving the cables room to room whenever I need them(about once a month) and I got tired of doing so,,[/QB]
it seems to me that we dicussed just in the right time. Good to hear that I could help you a little bit.
Regards, Christian.
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