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Old 10-01-2006, 13:31   #1
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Spdif, Toslink, optical.........?

I need a SpDif lead to connect from my Humax PVR to my Yamaha 757SE surround amplifier, but I have never heard of 'SpDif' before.
Is it just a optical to optical connection that I need.
I'm trying to buy a lead 5metres in length but there doesn't seem to be any SPdif leads.
Any help will be appreciated.

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Old 10-01-2006, 13:33   #2
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Moving to Home Entertainment Hardware forum...
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Old 10-01-2006, 14:36   #3
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It can be either optical or coaxial dependant upon what connections are on your product.
SpDif stands for Sony/Philips Digital interface. If your humax has an optical connection round back then use that, if it has both optical and coxial (RCA) then use whichever you prefer.

I would guess it is refering to a coaxial connection. i.e a 75 ohm RCA lead.

Last edited by Baz; 10-01-2006 at 14:38.
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Old 10-01-2006, 14:41   #4
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In fact here is some info.

Cabling details

S/PDIF (IEC-958) uses 75 ohm coaxial cable and RCA connectors. 75 ohm coaxial cable is inexpensive, because it is the same cable as used in video transmission (you can buy a video cable with RCA connectors to connect you S/PDIF equipments together). Coaxial S/PDIF connections work typically at least to 10-15 meter distances with good 75 ohm coaxial cable.

There also an optical version of S/PDIF interface which is usually called Toslink, because uses Toslink optical components. The transmission media is 1 mm plastic fiber and the signals are trasmitted using visible light (red transmitting LED). The optical signals have exactly the same format as the electrical S/PDIF signals, they are just converted to light signals (light on/off). Because high light signal attenuation in the Toslink fiberoptic cable, the transmission distance available using this technique is less than 10 meters (with some equipments only few meters).

Last edited by Baz; 10-01-2006 at 14:42.
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Old 10-01-2006, 14:49   #5
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Thanks for the info Baz. The Humax has a optical connection.
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Old 10-01-2006, 18:13   #6
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Quote:
Originally Posted by Baz
Because high light signal attenuation in the Toslink fiberoptic cable, the transmission distance available using this technique is less than 10 meters (with some equipments only few meters).
Hmm......that's strange I've got a couple of 10m Toslink cables and they both work perfectly.
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Old 10-01-2006, 20:23   #7
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Quote:
Originally Posted by Roswell
Hmm......that's strange I've got a couple of 10m Toslink cables and they both work perfectly.
Dont quote me on that its pulled from somewhere else.
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Old 12-01-2006, 10:32   #8
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Quote:
Originally Posted by Baz
In fact here is some info.
There also an optical version of S/PDIF interface which is usually called Toslink, because uses Toslink optical components. The transmission media is 1 mm plastic fiber and the signals are trasmitted using visible light (red transmitting LED). The optical signals have exactly the same format as the electrical S/PDIF signals, they are just converted to light signals (light on/off). Because high light signal attenuation in the Toslink fiberoptic cable, the transmission distance available using this technique is less than 10 meters (with some equipments only few meters).
Baz, where did you get this info? I'm quite sure it's not entirely correct. For a start, an optical cable does not have to be 1mm, and it does not have to be plastic. And I know the 10m thing is nonsense, I think a cable could pretty much wrap around the world without any problem at all.
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Old 12-01-2006, 11:51   #9
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Quote:
Originally Posted by Keiron99
And I know the 10m thing is nonsense, I think a cable could pretty much wrap around the world without any problem at all.
You could probably go more than 10m depending on the quality of the cable I'd guess. And no, you couldn't wrap it around the world unless the optic fibre had absolutely no imperfections and reflected all of the light internally without loss. That's why they still need to use optical repeaters for global communications.

Last edited by Nick dVl; 12-01-2006 at 11:51.
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Old 12-01-2006, 12:10   #10
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It was more to explain what SPDif was all about rather than the science behind optical cabling.
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Old 12-01-2006, 14:23   #11
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Well, as someone suggested, just use a cheap RCA lead and be done with it! Optical connections between hi-fi components are simply there for the "cool" factor rather than anything else.
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Old 12-01-2006, 14:36   #12
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I think it can be scientifically proven that when one or both of the components to be connected lacks digital coax connections an optical connection will generally sound better*




*unless listening to, for example Queen or Jeff Wayne, where disconnecting the connection can remove most of the unwanted "pomp"
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Old 12-01-2006, 15:37   #13
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Quote:
Originally Posted by Nick dVl
Well, as someone suggested, just use a cheap RCA lead and be done with it! Optical connections between hi-fi components are simply there for the "cool" factor rather than anything else.
Don't really think anyone think's optical is "cool" do they? [Edit - you're probably right. I can imagine people think optical=digital=good rather than a bit of cheapo copper wire] I think it's easier to physically accommodate optical connections on a lot of gear (especially portables). And probably a little cheaper too?

Apparently the best connection is I2S (which my DAC has), but it's very rare.

Last edited by Keiron99; 12-01-2006 at 15:39.
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Old 13-01-2006, 13:32   #14
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Quote:
Originally Posted by Keiron99
I think it's easier to physically accommodate optical connections on a lot of gear (especially portables). And probably a little cheaper too?
I would have thought it to be the other way round? Wouldn't you need an electro-optical convertor thingy and a diode (possibly a diode laser?)for the optical connection, rather than a more simple two-pin adapter?

Ah well, I'm waffling on again...

Last edited by Nick dVl; 13-01-2006 at 13:32.
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Old 13-01-2006, 19:06   #15
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Quote:
Originally Posted by Nick dVl
I would have thought it to be the other way round? Wouldn't you need an electro-optical convertor thingy and a diode (possibly a diode laser?)for the optical connection, rather than a more simple two-pin adapter?

Ah well, I'm waffling on again...
That seems to make sense, but fitting a phono socket on a personal stereo isn't going to be easy. You often get 3.5mm optical connections but there doesn't seem to be (to my knowledge) an equivalent mini version of the typical phono type connection for electrical.
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