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Old 23rd August 2011, 02:06 PM   #1
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Default Digital optical output, how to increase transmission length ?

Dear All,

After hours of reading the posts as guest, I decided to post to request your help.

Here my issue : I want to connect a Sony TVset KDL32EX711 to an Arcam rDac. The TVset has only a Toslink digital output, no coax.onboard
The real issue is the distance between the rDac and the TVset : 13 meters (39 inches).

The attenuation is too high along the cable and the DAC is detecting no source. I tested also with another source. This is the same result. I sent back the cable to the manufacturer for testing and polishing, there was no more results as they changed the cable.

After diging into the Toslink specification, I discovered the audio toslink modules are made for 5 meters or 10 meters transmission (TOTX147 & TOTX177 series). The needed cable is 13 meters ahead of that. The others modules from Toshiba have issues either on bandwidth (<15 Mb/s) or wave length (<> 650 nm)

In order to make this working, I would make one "Toslink extender" which allow higher transmission distance. However, I am not that much qualified in electronics.

The main idea is using the couple IF-E98 and IF-D97 from i-fiberoptics.

Those modules allow 75 meters transmission & up to 50 Mbits/s. This should be enough. One 74ACT08 logic gate between the 2 optic modules would clean the signal.

The overall propagation time between the input and output is 12ns + 10 ns + 7 ns. This means a total of 29ns delay in the optic channel. Do you think it will weak the signal and make the music worse ?

Do you think this would work ? Do you have any other idea ?

Thank you for your help
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Old 23rd August 2011, 02:39 PM   #2
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Toslink cable is usually simple high loss plastic. Literally try stuffing a 62/125 multimode glass fiber into the connectors and see what happens! There will be light loss as the sender expects a bigger surface area, but there is no loss in the receiver as all the light that gets in hit it. (I have tried this and measured the results!)


If that works you can find glass toslink cables that should be fine.
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Old 23rd August 2011, 02:48 PM   #3
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This could be a solution. Do you have any advise about a provider ?
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Old 23rd August 2011, 02:53 PM   #4
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Quote:
Originally Posted by T509 View Post
This could be a solution. Do you have any advise about a provider ?
Amazon list glass toslink cables.
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Old 23rd August 2011, 03:57 PM   #5
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This cable might be worth checking into. MyCableMart.com

Or perhaps this booster? http://www.mycablemart.com/store/car..._detail&p=2466
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Last edited by c2cthomas; 23rd August 2011 at 04:00 PM.
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Old 23rd August 2011, 04:09 PM   #6
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To all of you, thank you for reading and helping.

@ Simon7000
I will look deeper tonight about multimode fibers. After a quick look, i noticed the glass fiber toslink available are not long enough (I need 13 meters - 39 feets (not inches as I said ealier)). The true multimode fibers are delivered with not compliant connectors. The closest is the SC one but to big to fit the toslink plug.

@ C2cthomas
I have a 13 meters Viablue one which seems to be equivalent. ViaBlue™ toslink cable | H-Flex | aluminium plugs
My guess is my source has a 5meters capable transmitter. I am then asking too much to it.

The only toslink cable glass fiber multi strand of 15 meters I found is from Audioquest. But this is really overprices (>1650 €/ea)

Last edited by T509; 23rd August 2011 at 04:17 PM.
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Old 23rd August 2011, 04:16 PM   #7
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@c2cthomas About the booster, I am not sure that device will enhance the transmission distance as the optic modules used are unknown. That's why I was thinking doing it myself
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Old 24th August 2011, 03:01 PM   #8
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That repeater looks like just the thing - designed to do exactly what you want. At the price it's worth a try. Or maybe you can find something like this: Convertisseur Toslink optique vers coaxial at la FNAC. It may be able to push the signal thru 10 meters or more of coax. Use a high quality coax and it should be no problem.
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Old 24th August 2011, 04:08 PM   #9
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Thank you for the reply (and for the effort of the french link)

What I keep in mind from that thread :

- not trying to build my own repeater with the parts described earlier. This may be waste of time

- Changing the cable Viablue with another brand at the same quality may be an waste of money

- Testing a ready to use repeater is almost priceless : it worths the deal (althought not recommanded over 10 meters)

- Testing with a multimode glass fiber 62.5/125 can be a good option at relatively low cost (below 50 EUR)

- Switching from optical to coax is an expensive option as the box + the cable is almost 200 EUR.

I was maybe looking for a too complicated solution. I would try option 3 then 4. Thank you for your help.

Just to get your opinion, the circuit with the i-fiberoptics parts was imagined too simple ?
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Old 24th August 2011, 04:22 PM   #10
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No, not too simple. But I think you'll have better success with the coax cable. 13 metres is not too far. I use Canare L-5CFW coax for runs of 15-30 metres everyday with no problem. A cable like that with good RCA ends would cost me about $50. (35 EUR)
What can you find in Paris?

Also have a look here: http://www.bluejeanscable.com/store/digital-audio/
They can build it cheaper than I can.
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