# is "spdif" and "optical" the same thing?



## n0ah

i think i'm close to getting an audio gd compass to use with my hp laptop. i've read that optical is supposed to have slight edge over usb. my laptop has an "spdif" out and just wanted clarification.

 if they are in fact two different names for the same thing, can someone tell me exactly what wire/cord/adapter i need assuming the gd compass doesn't come with it? it's to be exclusively used with my laptop.


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## ford2

Quote:


  Originally Posted by *n0ah* /img/forum/go_quote.gif 
_i think i'm close to getting an audio gd compass to use with my hp laptop. i've read that optical is supposed to have slight edge over usb. my laptop has an "spdif" out and just wanted clarification.

 if they are in fact two different names for the same thing, can someone tell me exactly what wire/cord/adapter i need assuming the gd compass doesn't come with it? it's to be exclusively used with my laptop._

 



 Sony/Philips Digital Interconnect Format.= Optical.


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## linuxworks

spdif can be sent over optical or coax cable.

 spdif is the encoding. not the wire it runs over.


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## wavoman

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_spdif can be sent over optical or coax cable..._

 

and the coax can be terminated either with an RCA (should be 75 ohm, like a video cable), or a BNC connector.

 Careful -- the S/PDIF out from most motherboards is often terrible (I've seen DACs not be able to sync, or lose sync), the USB may well be better (unless you have added a third-party sound card).

 Anyway the audio gd compass accepts S/PDIF on either an optical or an RCA connector, and also USB.

 My bet is USB will sound the best.


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## tosehee

SPDIF is protocol and optical/rna/bnc is connector type (implementation).


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## tosehee

Quote:


  Originally Posted by *wavoman* /img/forum/go_quote.gif 
_and the coax can be terminated either with an RCA (should be 75 ohm, like a video cable), or a BNC connector.

 Careful -- the S/PDIF out from most motherboards is often terrible (I've seen DACs not be able to sync, or lose sync), the USB may well be better (unless you have added a third-party sound card).

 Anyway the audio gd compass accepts S/PDIF on either an optical or an RCA connector, and also USB.

 My bet is USB will sound the best._

 

AFAIK, the optical/rca sounds better than USB with Compass. Correct me if I am wrong.


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## wavoman

Quote:


  Originally Posted by *tosehee* /img/forum/go_quote.gif 
_AFAIK, the optical/rca sounds better than USB with Compass. Correct me if I am wrong._

 

It's the S/PDIF out of the HP laptop that I'm worried about!


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## ford2

Quote:


  Originally Posted by *linuxworks* /img/forum/go_quote.gif 
_spdif can be sent over optical or coax cable.

 spdif is the encoding. not the wire it runs over._

 

The OP's question was:is "spdif" and "optical" the same thing.

 I will stick with my reply:Sony/Philips Digital Interconnect Format.= Optical.

 Thankyou,now I will rest in peace.


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## krmathis

Nope, different things. Although they can be used in conjunction...
 S/PDIF is a digital audio data format, while optical is one method (hardware) to transporting the said audio data stream from A to B. 

S/PDIF - Wikipedia, the free encyclopedia
What is SPDIF?


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## linuxworks

Quote:


  Originally Posted by *ford2* /img/forum/go_quote.gif 
_Sony/Philips Digital Interconnect Format.= Optical.
	

	
	
		
		

		
		
	


	


_

 

this is wrong.

 but believe what you want, if you want to 'rest in peace' (huh??)


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## ford2

Quote:


  Originally Posted by *krmathis* /img/forum/go_quote.gif 
_Nope, different things. Although they can be used in conjunction...
 S/PDIF is a digital audio data format, while optical is one method (hardware) to transporting the said audio data stream from A to B. 

S/PDIF - Wikipedia, the free encyclopedia
What is SPDIF?_

 

Refering to optical out on a pc kindly tell me what else you can use it for.


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## linuxworks

the optoblocks can be used for MANY things. audio is just one of them.

 its just a led and a photo transistor at the other end.

 I've thought about using that cheap and easy (and ground-free) connect style for other things (other kinds of control channels for devices). it would work and be cheap to use, too.

 opto and coax are just physical transports.

 in fact, you can run video or mono-analog audio over coax. and you can also run digital spdif over coax.

 you can run digital spdif over fiber (opto). or diff pairs of wires (aes/ebu).

 but the 2 are different, the physical layer and the logical layer (maybe think of it that way). toslink and coax at .5v level is the PHY layer. redbook audio using spdif as the bit encoding is the LOGICAL layer above that.


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## krmathis

Quote:


  Originally Posted by *ford2* /img/forum/go_quote.gif 
_Refering to optical out on a pc kindly tell me what else you can use it for._

 

Indeed. Digital audio out...
 But that still do not make S/PDIF and optical the same thing... S/PDIF is for audio only, while optical can send any data traffic (audio, video, and much more).


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## brown274

What would be better or are they equal, or does it depend on component maker? Is (toslink) glass and (spdif) metal?

 1. SPDIF found on some laptops to a DAC
 2. Toslink from MacBook to DAC
 3. USB to DAC


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## linuxworks

toslink is plastic, by design and by implementation. anyone selling glass is not following standard spdif specs. glass is not 'better'. following the spec is better.

 spdif is a logical protocol. the way the bits come off some digital media.

 copper is copper. spdif is not copper. spdif can run over copper but it can run over toslink fiber, as well.

 when people say 'spdif' and they mean 'coaxial wire' they are being sloppy with the term.

 ethernet can run over copper (twisted pair, even coax) and also fiber (100baseF). but the packet data is still called ethernet. digital audio is a bit like that. spdif is the signal and it can 'ride' on various physical media.


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## wavoman

*linuxworks* makes an important point about grounding.

 I was having all kinds of SPDIF dropout problems over coax, despite very careful wiring, proper 75 ohm RCA terminations, etc. With the help of engineers marshalled by customer support at Wadia and Sonifex, we traced this to a ground difference issue. Converted to SPDIF over TOSLink optical for the last leg and problem gone! Optical is optical, so there is no ground!!

 I am falling in love with TOSLink all over again. We first slept together in the '80s, when SONY gear only had optical outs, but I left her for coax. Something about that RCA male plug and the female connector ... you understand. But like every fling motivated only by the physical side, it ended badly.

 BTW, Wadia pushes a glass optical SPDIF spec ... they are big believers in it. They would agree it is not the same as (plastic) TOSlink optical ... they offer both (as well as 75-ohm coax SPDIF with BNC and 110-ohm AES/EBU with XLR) on their CDPs (as outputs) and inputs on their DACS (DACS built in to CDPs but accessible).


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## linuxworks

all good coax spdif ends (both sender and receiver) should use pulse transformers. that way there are no ground loops on the beloved coax, as well.


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