# AES/EBU vs SPDIF



## Orpheus

hey, i was wondering... which one would theoretically result in better performance?--AES/EBU via XLR's, or SPDIF via RCA's?

 i'm getting a Grace 901 (arriving monday... yeah!!!)... and my CD player has both types of outputs. i would assume that AES/EBU is better, but heck, i learn a lot here.... so i figure, what you guys think?

 oh yeah, would it make a difference that i need a 15-20ft cable?--i think the AES/EBU's carried on a balanced line right?--is that for noise rejection or for other technical reasons?

 (also, it's generally accepted that optical is inferior to normal cable for SPDIF right?)

 thanks.


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## fiddler

From my understanding, when you do have the choice, AES/EBU will provide better results. Why, I'm not sure, but I would think for many of the same reasons balanced is better than single-ended in analog. (Mostly reduction of noise, as you mentioned in the balanced/unbalanced thread.)

 BTW I read your WTB thread, you might consider doing something like this:
http://www.venhaus1.com/aesebu.html


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## Orpheus

yeah, i would make the cables.... but i'm a little weary of impedance problems, which i know digital is sensative to. i still have yet to read the article someone submitted to me about cable impedances, cause i still don't understand how cables are measured for impedances (i mean, when you measure a cable, it's almost 0 ohms......... so, maybe you can briefly explain what impedance for cables actually measures?--that's would be cool.)

 anyway... that's why i want to get a well-known cable like apogee's... then i don't have to worry about these impedance issues. i mean, you can just stick any XLR terminated audio cable in there right?


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## Mastergill

I would use AES/EBU. I don't know if SPDIF is inferior, but for data transmission i would better have XLR plug. I think the quality of the signal must be the same, so choose the best kind of plug and bigger built cable.
 (Note that for analog i like better unbalanced, i'm not an XLR/balanced fanatic ).
 If you have both output you can make an easy comparison.

 You're right, forgot optical output. Even real glass one, because of electro to optical conversion.

 I think you need a Cardas AES/EBU cable at $200 for 0.5 meter.


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## fiddler

Oh, that's "characteristic impedance" which is different from the resistance of the cable (which is as you mentioned usually next to nil).

 Erm, I think I have it right: it's basically a function of inductance and capacitance, and its a constant value regardless of the length of the cable. 

 I think the formula is sqrt(L/C), L is inductance per unit length, C is cap. per unit length. Don't quote me on that, I just got that from the AA cables forum just now. I do believe it's more complex than that simple formula because characteristic impedance changes with frequency. Quite a lot of it is way over my head, but I believe if you use a cable like the Belden one Chris Venhaus recommends which is rated at 110 ohms char. imp., you should probably get quite good results.


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## needgoodphones

Cable Impedance


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## Orpheus

Quote:


 I think you need a Cardas AES/EBU cable at $200 for 0.5 meter. 
 

 see above: i need 5m. 
	

	
	
		
		

		
		
	


	




 .....hmm, so $2000?..... that costs more than 2x of the amp!

 okay..... thanks for the impedance information guys........ gotta read up now


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## Sean H

Search the old stomping ground too.


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## jefemeister

The balanced cables are generally thought to be better than the single-ended ones. This really only has to do with transmitting over long cable runs. It's the same concept as XLR vs RCA analog cables. The opposing phases' fields cancel each other out. If you're running 20' you have no real option other than balanced. Over short cable runs (1m or so) I have not been able to detect significant differences in quality between the two for digital. I do maintain that balanced cables *always* sound better for analog though. but this is more a function of the differential comparators within the equipment than the cable itself IMO.

 The best digital transmission is by far glass optical. It's index of reflection is as close to 1.0 as possible. It is also practically immune to noise. Well worth any expense in the electrical to optical conversion which is rather trivial anyway. That said, plastic optical (toslink) is about as bas as you can do because a lot of signal energy is lost during transmission and refractions within the cable can "corrupt" the data to some extent.

 edit: you can easily run 100' of glass fiber losslessly with a minimum amount of jitter, noise, etc.


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## lan

aes/ebu besides having good noise rejection also is a hotter signal. i'd go for that.

 what made you get the grace?


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## Orpheus

Quote:


 you can easily run 100' of glass fiber losslessly with a minimum amount of jitter, noise, etc. 
 

 i heard that glass fiber is fragile though. i mean, i'll be running the stuff under chair matts and it will be twisted and abused... would it survive constant stomping and bending?
  Quote:


 what made you get the grace? 
 

 cause it's the best solid-state amp ever made. 
	

	
	
		
		

		
		
	


	




 heh he. just kidding. cause i've read some very favorable reviews from trusted sources (john atkinson of stereophile, and from professional mags like Mix)... and i've seen the measurements. this thing is near perfect. PLUS... it has balanced ins, which almost none of its competitors have. and the digital ins are nice, though admittedly, i could live without them. but i figure, heck, it has digital ins, might as well try them out.


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## jefemeister

> _Originally posted by Orpheus _
> *i heard that glass fiber is fragile though. i mean, i'll be running the stuff under chair matts and it will be twisted and abused... would it survive constant stomping and bending?QUOTE]
> 
> I have a lot of experience with AT&T ST fiber. It can take a lot of abuse. I don't know if I'd jump up and down on it, but you can easily tie it in a loose knot without it breaking. The big thing to watch out for is that the exposed fiber ends do not scratch in even the slightest. It is also important that the jacket is intact so that the fiber itself doesn't scratch. This type of cable I'm talking about uses a special ST connector that not a lot of manufacturers support because it's a pricey interface and cutting/termination is next to impossible.
> ...


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## gerG

Dean, congrats on an excellent choice! You are going to fall in love with the Grace.

 I have been playing cable games, and I haven't heard any audible difference between the 3. The only degradation I have found is if I unplug the optical cable and start pulling it out of the socket. The signal still crosses the air gap up to about .25", then it just drops out.

 I would recommend the AES, just because it has the wonderfully tolerant XLR connectors. You should get the 110 ohm digital cable, but for 20' a plain old microphone cable will work just fine. The pros actually switch to s/pdif for really long runs (500' and up) but I can't remember why. I will try to recall.

 I will buy/build a long optical cable some day, but those will always be more fragile than stage cables.

 Jeff, you just identified yourself as a resource for optical cable fab! Any thoughts on using an actual coupler with a toslink rather than the standard polished fiber ends? I like the idea of a single glass fiber in a very tough jacket.


 gerG


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## Orpheus

Quote:


 The pros actually switch to s/pdif for really long runs (500' and up) but I can't remember why. I will try to recall. 
 

 that's interesting.... are you sure about this??? logically, i would think the other way around, since AES/EBU is the balanced version right? very strange....

 ....but alas, it seems i don't need to query about this anymore... i just checked and my cd player actually only has aes/ebu INPUTS! stupid. so i guess i'm gonna get spdif afterall--i looked at atkinson's measurements of the grace in stereophile, and it indicates that jitter rejection via toslink is worse than via spdif. so, i'm gonna go pick up a spdif cable by apogee this weekend.

 however, the grace has a switch to choose between spdif and aesebu right? cause i plan to use the aesebu to connect to the computer's audio interface, and the spdif to the cd player. i think that should work out well for me.

 dang... can't wait till it arrives on moday!

 ....you know, i really wish the grace had outputs to take advantage of what seems to be a really good dac. oh well. guess it fits in its price point well, cause the 904? is only $1000 more and adds a zillion features....


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## jefemeister

Quote:


 _Originally posted by gerG _
*
 Jeff, you just identified yourself as a resource for optical cable fab! Any thoughts on using an actual coupler with a toslink rather than the standard polished fiber ends? I like the idea of a single glass fiber in a very tough jacket.* 
 

I did? I'm happy to help out any way I can, but I didn't mean to imply I was an authority on the subject 
	

	
	
		
		

		
		
	


	




 We buy our cables from normal distribution channels, nothing fancy. Also, I'm not sure I understand your question. Do you mean you want a glass cable w/ a different termination?


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## gerG

I was refering to a different termination, sort of. Most of the fiberoptic systems that I have run across use a coupling device of some sort, usually a small spherical lens, to maximize coupling efficiency. Toslink just seems to use a large aperture to catch sufficient light to get the job done. I was guessing that a more efficient connection would make a low cross section fiber feasible.


 gerG


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## Orpheus

just ordered an apogee 3m spdif and 3m aes/ebu. ............getting my grace monday, cables will be in by end of week. ..............finally, no more headphone stuff. heh he.


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## ginetto61

Hi !  very interesting subject indeed. 
In this review   * https://www.computeraudiophile.com/ca/reviews/Berkeley-Audio-Design-Alpha-USB-Review/*  i found the following opinion 
"Berkeley Audio Design strongly recommends using the balanced AES output of the Alpha USB when possible. In theory a true coaxial 75 ohm S/PDIF connection is better, all things being equal. However, all things are not equal in practice. Given that balanced AES does not use true 110 ohm connectors I inquired into this recommendation a bit further. The answer I received from Michael Ritter was mainly voltage, and some noise rejection. Even though S/PDIF when implemented with 75 ohm BNC connectors is a true 75 ohm coaxial connection its limitation is that it delivers .5 volts peak to peak. Balanced AES on the other hand benefits from a 2 to 7 volt signal amplitude. In fact the Alpha USB's AES output delivers 4 volts or eight times the signal level of the S/PDIF output. This higher voltage is key to maximizing data receiver performance and reducing effective jitter. The balanced AES connection also offers common mode noise rejection"

From what i understand the Berkeley Audio Design Alpha USB converter is a very fine unit still for today standards.


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