# Best for my CD > DAC - Optical or Coaxial digital?



## Bencrest

Probably a simple question, but I'll ask it anyway!

 When I get back home next month, I'll be wanting to connect my Sony CDP (XB930 QS) to my new Cambridge DacMagic ('08 edition) to see if it makes any difference in SQ.

 I can use either Digital Coaxial (RCA), or Optical (TOSlink) connectors, as the CDP has both.

 *BUT* - would either of them have any appreciable advantage over the other, seeing as how ICs aren't particularly expensive for either?

 Cheers


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## myinitialsaredac

Not another oO.

 My advice would be try both and return the one you dont like.

 As for the arguments,
 optical has no dialectric in the cable ridding it of dialectric dispersion/absorption yada-yada, has plenty of bandwith for 16/44.1, has no commong ground, and is immune to e.f.i. because its light. The problems with optical are the extra bit-->light pulse conversion, length issues, no right angles, fragile, and the implementation of the reciever/transmitter. 

 Coaxial is good because it is that natural state of bits 
 (electrical pulses), can be run long long distances, and has more bandwith (though that isnt a huge issue with 16/44.1), not fragile, can do right angles fine. The problems are it uses a common ground which can cause reflections and smearing and yada yada, dielectrics so you get dielectric dispersion/absorption, the skin effects, and it is susceptable to efi if its not shielded properly.

 Both have their positives and negative, It all depends on what you like in your system. My own opinion is that I prefer toslink, but if you are running >5feet you need to think it through (right angles also will kill toslink) and >10 feet you need to go coax. 

 So just test em =D

 Dave


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## Golden Monkey

Well put, Dave. It's pretty much six of one, half dozen of another - there's VERY little difference (indeed, if any), all things being equal, but specific situations would require one over the other.

 Personally, I like coax. I don't like converting more than I have to.


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## krmathis

Here we go again!
 The never ending optical vs. coax digital discussion... ** Shakes head **

 I prefer optical. Because it electrically shield the DAC from the transport, which makes sense to me as my DAC and amplifier are off-grid.


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## HeadLover

amm, COAX?


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## krmathis

Quote:


  Originally Posted by *HeadLover* /img/forum/go_quote.gif 
_amm, COAX?



_

 

Coaxial cables are quite popular for digital audio transfer, you know.
 Using either BNC or RCA connectors.


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## HeadLover

Quote:


  Originally Posted by *krmathis* /img/forum/go_quote.gif 
_Coaxial cables are quite popular for digital audio transfer, you know.
 Using either BNC or RCA connectors.




_

 

Yes I know what it is 
	

	
	
		
		

		
		
	


	




 I mean, I am using COAX

 But, right now I am trying optical.
 amm, sound the SAME ?!

 I think optical is better when using sound out of a PC, much less dialectric problems (none) compare to COAX

 Not?
 I think it is better for a PC, what do you think?


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## krmathis

Quote:


  Originally Posted by *HeadLover* /img/forum/go_quote.gif 
_Yes I know what it is 
	

	
	
		
		

		
		
	


	


_

 

You asked a question, hence it was obvious to me that you did not know what it is...
 Oh well, at least you do now


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## HeadLover

Quote:


  Originally Posted by *krmathis* /img/forum/go_quote.gif 
_You asked a question, hence it was obvious to me that you did not know what it is...
 Oh well, at least you do now_

 

Yep sorry 
	

	
	
		
		

		
		
	


	




 I mean that he should use COAX

 Any way, optical is better running audio from a PC, right? or what?
 What do you think??


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## krmathis

^ I don't think anyone are in general "better".
 As most other audio related it all comes down to personal preferences, and the features of the gear you use.

 Some prefer coaxial, some prefers optical, and even some prefer USB.


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## HeadLover

LOL
 I have tried both, and sound same for me
 So, right now using COAX, maybe less converting on the way will do better to the audio


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## Pars

You can't say for sure on any given setup what will sound better. Most users prefer coax, but it really depends. The entire link (transmission circuitry / cable / receiving circuitry) is really a system. Most equipment is not done properly in terms of interfacing a 75 ohm transmission line (search for spdif and Jocko on diyaudio if you want to know more). And because of the embedded clock, running at ~2.8Mhz for 16/44.1 digital audio, it is really an analog RF signal, not a simple digital (only 1's and 0's matter) signal. BTW, coax should be a minimum of 1.5m long to minimize reflections. If you can make your own cables, try a long (>2m) vs. a short cable and see if you hear any difference. If you don't hear any differences, count your blessings 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *krmathis* /img/forum/go_quote.gif 
_<snip>




_

 

That is a 50 ohm BNC in the picture...


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## krmathis

Quote:


  Originally Posted by *Pars* /img/forum/go_quote.gif 
_That is a 50 ohm BNC in the picture... 
	

	
	
		
		

		
		
	


	


_

 

And?
 Example picture to show 'HeadLover' what a coaxial digital cable could look like. Since he did not seem to know what it is. Picked this one since it has both connector types, BNC and RCA.

 The 50 ohm number don't tell me anything...


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## Pars

SPDIF spec is 75 ohms... if you are buying cable for digital audio (SPDIF) and you go with BNC because it is (or can be) a real 75 ohm connector vs. an RCA which can't, you don't want to go buy one with a 50 ohm connector on it


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## krmathis

Quote:


  Originally Posted by *Pars* /img/forum/go_quote.gif 
_SPDIF spec is 75 ohms... if you are buying cable for digital audio (SPDIF) and you go with BNC because it is (or can be) a real 75 ohm connector vs. an RCA which can't, you don't want to go buy one with a 50 ohm connector on it 
	

	
	
		
		

		
		
	


	


_

 

Ok, thanks. I learned something new. 

 But as said it was just an example picture showing a coax cable with BNC and RCA plugs, so that 'HeadLover' could see what it looks like. The intention were not that he should walk out buying this exact cable...


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## 1UP

OP, technically coax, but a big variable is how good/bad that Sony's coax out is! Stereovox is one of the best S/PDIF cables I've tried.


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## meat01

Quote:


  Originally Posted by *1UP* /img/forum/go_quote.gif 
_OP, technically coax, but a big variable is how good/bad that Sony's coax out is! Stereovox is one of the best S/PDIF cables I've tried._

 

I wouldn't say this is a big variable. You really don't need to spend $100 to transfer a digital signal. You need good shielding and good terminations, which most coax cables have.

 I did not pay $100 for the cable that is connecting digital HDTV to my cable box or the the cable box to the wall and it transfers a 5 channel Dolby Digital audio signal *and* an HD video signal perfectly. I think the Sony coax can handle 2 channel audio.

 I am curious, what makes the Stereovox the best cable you have heard?


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## HeadLover

Can you also provide link to the Stereovox you are talking about? and price?


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## 1UP

Sorry guys, missed the trail-end of this thread. 

 S/PDIF is a RF transmission line / protocol; each step in the line from transmitter to receiver is what determines its quality or lack of it which we'd measure as jitter and hear as cruddy sound. In contrast and IME, a nicely done implementation gives the sound great focus and musicality.

 The best S/PDIF cable I've used is my ART Ubyte (16ft BNC-BNC); the next best is the Stereovox HDXV - now the XV2.

 The best posts to elucidate what I've written can be gleamed here and here. Pat is Jocko Homo from diyaudio and diyhifi, he is an acerbic RF engineer...with a TDR...and a great product 
	

	
	
		
		

		
			





 When I was pointing a finger at the Sony's coax output, I was simply saying that as the TX end of the line, it could suck horribly, or be OK - this would certainly determine whether coax is comparatively going to be "better" than its optical, in this case. 

 ART's Ubyte is $200 and I think the Stereovox is about the same. I just moved to the USA from the UK; seriously sold all my hi-fi gear (including my HDXV); the only thing I kept was the ART S/PDIF cable! Now for the rest!


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## 1UP

To state the other side of the argument (digital cables / protocols don't make much difference) - this view is more coherent when the DAC considered reclocks (e.g. the Benchmark guys always maintain the DAC-1 is jitter and cable immune and also indifferent to what connection is used). 

 All I can say is I haven't found the DAC-1 to be 100% immune to partnering equipment, though I do feel it is less variable to such things than other gear out there. Further, not all DACs out there have similar reclocking/anti-jitter circuitry.


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## myinitialsaredac

Well put 1up.

 That is really the issue for all of the "what is best" questions. It is dependant upon your specific system and preferences, there are too many variables to declare a winner. In a perfect world they would both sound the same, but unfortunately life isn't perfect.

 I'd venture to say even the dac-1 wouldn't sound great with a 50 ohm rca cable. If I recall correctly the dac-1 also isn't utilizing bulk mode transfer with a huge buffer either so it is still susceptible to some degree.

 Dave


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## krmathis

Quote:


  Originally Posted by *myinitialsaredac* /img/forum/go_quote.gif 
_Well put 1up.

 That is really the issue for all of the "what is best" questions. It is dependant upon your specific system and preferences, there are too many variables to declare a winner. In a perfect world they would both sound the same, but unfortunately life isn't perfect._

 

Exactly! 
	

	
	
		
		

		
		
	


	



 It all comes down to personal preference, and the audio gear used.


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## sahwnfras

Quote:


  Originally Posted by *Pars* /img/forum/go_quote.gif 
_SPDIF spec is 75 ohms... if you are buying cable for digital audio (SPDIF) and you go with BNC because it is (or can be) a real 75 ohm connector vs. an RCA which can't, you don't want to go buy one with a 50 ohm connector on it 
	

	
	
		
		

		
		
	


	


_

 

Are you sure about that comment on RCA connectors. Im sure that a video signal is 75ohms. And im sure if it was really not a true 75 ohm connection then high end company wouldnt even bother with it, but i see it commonly used on high end equipment. But correct me if im wrong.


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## 1UP

Yes. RCA connectors are typically 30ohms. Many manufacturers are either ignorant or basically misleading consumers cause their overpriced out of spec cables otherwise wouldn't sell.

Reasonably inexpensive soundcard with bit-perfect COAX output? - Head-Fi: Covering Headphones, Earphones and Portable Audio


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## sahwnfras

um

Tributaries Cable

Tributaries Cable

 And as i said before i am sure a video connection is a 75 ohm connection, and i think a sub woofer is a 115 ohm connection.. and they both use a rca connection. I know that Linn gear does use rca connections, and if you are familiar with Linn you know that they would not sacrafic anything it terms of sound quality.

 And it seems form your bs forum links, that it is possible with a proper male and a proper female connector.

 And really for the OP just try out both te coax and the optical and let your ears be the judge, audio cannot be compared over the internet.


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## 1UP

sahwnfras - read those links again - it's not bs, tyvm.

 The whole point is you can use 75ohm video cable as the cable but normal RCA connectors will ruin the desired impedance. Also just having custom RCAs on the cable isn't enough to maintain that impedance when the mating connectors on your components are not also moulded the same. 

 You have to think along the entire transmission line.

 Whereas with BNC it just de facto IS 75 ohm so why bother paying for a WBT type megabucks connectors when BNC is the right connector for the job.


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## Pars

sahwnfras: do you really believe everything you read, in marketing literature particularly, from companies trying to sell you something? They can say anything they want (our cables are 75 ohm, blah blah) and some (well, probably alot) of people will believe them. As you yourself said, trust your own ears. If you hear differences, particularly between digital cables, ask yourself why... and don't be blinded by BS, because there is an awful lot out there.


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## sahwnfras

Well i put those up ther because i work with those cable and have tested them.

 But 1Up you say BNC is the end all be all, but really couldnt you have a low quailty BNC and lose impedance. Just as with a low quality RCA you can lose quality. Now these WBT things people keep mentioning i have no idea What they are. 
 I just believe that if you use quality parts you can get the job done right. And it will never be cheap lol


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## 1UP

I'm not saying it's the be all and end all, and I'm not advocating that it is cheap or expensive. 

 Either something is rated for 75ohm impedance or it is not. BNC can be, and if rated so (rather than say 50 ohm), it's virtually guaranteed to be so. Run of the mill RCA won't, can't and isn't going to be. Any RCA jack that claims to be, is going to be more expensive than even the most expensive BNC, AND won't give a fig unless its mating chassis connectors are also designed to be 75 ohm. Again, these will be more expensive (e.g. WBT connectors) than even the most expensive BNC.

 An Amphenol BNC jack costs $6 from Digikey - a WBT 0152 AG what $50, $100??!!


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