SPDIF v L/R/C Channels

~J~

~J~

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Gonna pass this question on to you experts 'cos it has me baffled!!

Recently I've changed my sound setup so I can use optical input from my Xbox360 to a Creative DTT3500 Amp.

The back of the amp didn't have the usual Left-In, Right-In, Centre-In, only 3 input types: Digital In, SPDIF In and Optical In.

I couldn't be bothered installing the Soundblaster 2 with the Digital Out, but did note that my motherboard had a SPDIF Output, and so connected the lead (just one) from the motherboard to the amp which a first-time success.

What exactly IS SPDIF? Is it similar to Optical only passing an electrical current rather than an optical one?

I'm looking to build my own media centre in the near future, would I be better off looking for a motherboard that has both SPDIF Out and Optical Out rather than the usual multi-channel 5.1 sockets?
 
SPDIF is more a signalling protocol, designed for carrying digital audio data in a bitstream. The physical connection can be electrical (RCA/Phono, or BNC are commonly used, but can be carried over other formats too), or optical.

Its quite a robust system, some people have even managed to use wireless video transceivers to get spdif around their houses without using long cable runs. Other people have jury rigged SP/Dif over Cat5.

While there is a never ending debate over which is best, I find on my Tag Maclaren AV32R the coaxial inputs sound slightly better than the opticals.
 
The only thing you need to bare in mind about using optical etc from onboard sound is that it will only be stereo (unless playing from a DD5.1/DTS source eg dvd's) - you need to have a dd5.1 encoding sound card or the 3x stereo jacks to get 5.1 sound from PC (the exception being the creative connector on the back of creative amps which should do 5.1 if connected to a creative card)
 
Corasik said:
While there is a never ending debate over which is best, I find on my Tag Maclaren AV32R the coaxial inputs sound slightly better than the opticals.

I think your ears are deceiving you! No matter whether you use coax or optical, the payload in the bitsream is identical. So unless one type of cable is so rubbish as to be introducing errors into the stream they will both sound identical - and any any cable that can't do less than 2Mb/s error free over a couple of metres really belongs in the bin. A one is a one and a zero is a zero, you can't get 'better quality' ones and zeros. It's a bit like saying that the print quality on a printer improves when you change from Centronics to USB!
 
While the 0's and 1's may be the same, jitter is different on optical V digital. Jitter is errors in the timing, in computing this doesnt matter, as the computer waits for all the bits it requires to arrive, and computers can even retry if there is an unfixable error is detected.

On the other hand the DAC expects a perfectly timed sequence of 0's and 1's and if there's an error, the dac just says, ah I'll just give my best guess, there is no time to wait and have a retransmission. Jitter can come from the transport itself (Drive/Laser mechinism), the SP/DIF interface, even the cables. Jitter can also be caused at any time while the audio signal is in the digital domain.

Jitter test's are commonly used in the telecomunications industry, to test any digital equipment carrying digitally encoded audio/speach signals. Read a nice website I found via google the other week, where finally someone hooked up a jitter tester to a number of CD transports, and DAT's and explained very clearly how important good transports, and cables can be.
 
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