TOSLink Cables All the same? Any degradation over Length? - Page 3 - diyAudio
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Old 18th August 2002, 04:29 PM   #21
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hifiZen is right. TOSLINK is inferior to coax, the interface is highly unreliable, and it is not single-mode (it is multimode).

ANY transmission method can be plagued by poor interface and/or impedance irregularities. Fiber is especially susceptible in short lengths as too much energy is reflected back from the receiving end. This causes the light source (which in the case of TOSLINK is really cheap) to do all manner of wierd things. The end result is pulse distortion, which then translates into jitter.

Quote:
S/PDIF is based on AES/EBU which is a real-time digital transmission protocol for use in studios, often over high quality balanced cabling.
How to make a bad idea worse.........

The original version of this kludge allowed for, I believe, something stupid like 3 transmitters and up to 7 receivers on a single line. Obviously, no one is this group knows squat about transmission lines. If they did, they would not have chosen an XLR connector for a 110 ohm transmission line. Nothing high-quality about how this is done. The cable may be nice, but on the whole, it stinks.

And you wonder why recordings sound terrible these days.......

Jocko
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Old 19th August 2002, 07:09 AM   #22
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Default Re: Error correction? What error correction?

[QUOTE]Originally posted by Daryl Low
[B]The S/PDIF format has at best a parity bit. This is *NOT* an error correcting code! The big difference between S/PDIF and other "reliable" digital protocols is that S/PDIF is unidirectional with no flow-control.

S/PDIF is based on AES/EBU which is a real-time digital transmission protocol for use in studios, often over high quality balanced cabling. With that in mind, the protocol designers decided they could sacrifice error detection / recovery for better real-time response. After all, studios could better afford the expensive cabling and equipment.
--------------------------------------------------------------------------

Whatever the specs, AES/EBU cables also sound different; nearly as much as SPDIF. As does 75R BNC connections! I2S seems to be better although there are not many I2S (enhanced) cables.
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Old 19th August 2002, 08:09 AM   #23
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I would hope I2S would sound better, as one does not have recover a clock from a serially encoded pulse train loaded with interface problems.

And speaking of 75R BNCs.....let me say it again.....for those who might be new....

There is no such thing as a 75 ohm RCA. Anyone want to prove me wrong?

SPDIF with proper 75 ohm cables, connectors, and terminations is the only way this format can sound good.

Jocko
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Old 19th August 2002, 10:11 AM   #24
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Quote:
Originally posted by Jocko Homo
There is no such thing as a 75 ohm RCA. Anyone want to prove me wrong?
What not even if you take a 75-Ohm BNC and change the plugs?
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Old 19th August 2002, 10:59 AM   #25
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The impedance must match along the entire cable, including the plugs. Even if only the end of the cable is an impedance mismatch you'll still get reflections.
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Old 19th August 2002, 01:03 PM   #26
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Jocko, some time ago in some other thread you mentioned that the receiver end on the Toslink can also be much improved compared to the standard way thay are done. Can you give some pointers of what you had in mind....

I know it's not the best way to transoprt a signal but I'm planning a new DAC in my head and Toslink would be used only for signal coming from PC. There I think it's not too bad as it decouples the grounds and PC's is a very noisy one.

Ergo
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Old 19th August 2002, 02:43 PM   #27
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Default Re: TOSLink Cables All the same? Any degradation over Length?

Quote:
Originally posted by Schmanthony
Hi,

I'm more than willing to abmit I don't know what I'm talking about...
Ok, I know very little in this matter scienticly. I suspect that much of what has been said here are opions, nothing more. Does optic fibres really have problems with reflexions? Which factors are really degrading for the sound so you can actually hear it?

One thing is for sure: There are differencies in mechanical strength. A pro has gone mad with TOSLINK with it's tiny plastic also the short transmission length. There are also differencies in electrical characteristics but it's very seldom reported.

Discussing specific components and particular cables creates always hot debates. I wonder why? Also there are lot's of people out there who wants to make money of this which I don't like.
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Old 19th August 2002, 02:48 PM   #28
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Quote:
Originally posted by Jocko Homo

There is no such thing as a 75 ohm RCA. Anyone want to prove me wrong?
You probely very right since RCA plugs originally not was intended for mathced impedance situations but, hey, how important is this fact really when we talk about rather low frequencies (low bit rate) and short mechanical length of the plug?
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Old 19th August 2002, 02:58 PM   #29
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Quote:
Originally posted by peranders


You probely very right since RCA plugs originally not was intended for mathced impedance situations but, hey, how important is this fact really when we talk about rather low frequencies (low bit rate) and short mechanical length of the plug?
What is the transmitter rise time? 4ns? 0.5/4ns=> frequency content to 125Mhz, regardless of bitrate. I don't know how bad the mismatch is to calculate the reflection...any figures from you Jocko?
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Old 19th August 2002, 08:14 PM   #30
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[QUOTE]Originally posted by Jocko Homo
[B]I would hope I2S would sound better, as one does not have recover a clock from a serially encoded pulse train loaded with interface problems.

There is no such thing as a 75 ohm RCA. Anyone want to prove me wrong?

SPDIF with proper 75 ohm cables, connectors, and terminations is the only way this format can sound good.

----------------------------------------------------

The issue is: what is good? In my experience, RCA terminated cables can sound good when compared with the same cable terminated in BNC. Some very expensive and highly touted cables consistently sound wrong over a range of systems and terminations. Time the industry sorts out the interfacial problem. There is enough money in it!
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