# stereo XLR???



## AlexD (Dec 12, 2011)

is it possible to run a stero signle though an XLR conecter? it has 3 cores. if it can why isnt it used? i have never seen an XLR being used as stero.


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## gcpsoundlight (Dec 12, 2011)

There is no electrical reason not to, I have done it myself. The trouble is you effectively have 2 unbalanced lines, which means that you will be much more susceptible to noise pickup. Also, if you put phantom power on, you will blow what ever is on the other end. Having said that, you shouldn't put it on a mic channel, the only way I run stereo down a mic cable is to have a y split at each end. 


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## museav (Dec 12, 2011)

AlexD said:


> is it possible to run a stero signle though an XLR conecter? it has 3 cores. if it can why isnt it used? i have never seen an XLR being used as stero.


XLR connectors are readily available with 3, 4, 5, 6 and even 7 pins and I have done stereo audio on 6 pin XLRs. The reason you don't see it being done on 3 pin XLRs is probably because XLRs are used primarily in commercial or professional applications which also typically utilize balanced audio.


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## bishopthomas (Dec 12, 2011)

Most stereo microphones come with a 5-pin connector and breakout cable. So, to answer your question: Yes, with the appropriate connector (3 pin for unbalanced, 5 pin for balanced).


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## Stookeybrd (Dec 12, 2011)

XLR is the go to cable/connector for balanced audio which requires three conductors: positive polarity, negative polarity and ground. We could just as easily use a TRS for balanced audio transport, but for various reasons the XLR has become the King. If you were to send two audio signals down a single XLR then the signal would be unbalanced and would be susceptible to interference, wouldn't have any where near the same distance available, and would have much lower signal to noise ratio. It's doable, but not worth the sacrifices to save a little bit of cable.

History of the XLR.


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## gafftapegreenia (Dec 12, 2011)

Stookeybrd said:


> XLR is the go to cable/connector for balanced audio which requires three conductors: positive polarity, negative polarity and ground. We could just as easily use a TRS for balanced audio transport, but for various reasons the XLR has become the King. If you were to send two audio signals down a single XLR then the signal would be unbalanced and would be susceptible to interference, wouldn't have any where near the same distance available, and would have much lower signal to noise ratio. It's doable, but not worth the sacrifices to save a little bit of cable.
> 
> History of the XLR.



Good article and a great website there. Bookmarked.


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## WooferHound (Dec 13, 2011)

The two inside conductors are not individually shielded and will Crosstalk a Lot if used for stereo.


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## AlexD (Dec 13, 2011)

WooferHound said:


> The two inside conductors are not individually shielded and will Crosstalk a Lot if used for stereo.


 
Im not the most knowledgeable about cable science  But looking at a standard mini jack to stereo pair 1/4inch jack it docent seem to be shielded. or am i being dim? (lighting pun?  

Thanks for the response guys  6 pin had completely left my mind


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## Nelson (Dec 13, 2011)

What cable did you use for the six pin? Where did you find it?

Edit: I agree, that was a nice history of the XLR. I still have a few original Cannon XL connectors in use. Still work well to this day!


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## bishopthomas (Dec 13, 2011)

Just use a 2 channel snake wired appropriately. Or I would probably use two install grade mic cables with heat shrink and expandable sleeving.


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## FMEng (Dec 13, 2011)

museav said:


> XLR connectors are readily available with 3, 4, 5, 6 and even 7 pins and I have done stereo audio on 6 pin XLRs. The reason you don't see it being done on 3 pin XLRs is probably because XLRs are used primarily in commercial or professional applications which also typically utilize balanced audio.


 
Not to mention that if you put unbalanced, stereo into one end, and accidently plug it into a balanced, mono input, any audio to both channels would cancel out. Vocals, bass, kick drum, and lead instruments would dissappear in from most mixes. If a manufacturer built equipment with such an interface, it would lead to frequent mistakes.

Just to make the discussion more fun, AES3 digital audio IS STEREO on one, 3-pin XLR connector.


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## waynehoskins (Dec 13, 2011)

FMEng said:


> Just to make the discussion more fun, AES3 digital audio IS STEREO on one, 3-pin XLR connector.


 
That was one of my first thoughts. I'm curious, is is sum-and-difference stereo like we use in stereo FM, or is it two discrete full-bandwidth channels? I had thought of using AES for interconnection between two digital consoles on a show I'm working on now, to send two unrelated channels from console 1 to console 2, and bringing back four unrelated channels from console 2 to console 1. It never came to pass since console 2 doesn't have AES outputs like I thought it would, so we are incurring the excess A/D and D/A conversions I hoped to avoid.


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## Stookeybrd (Dec 13, 2011)

AlexD said:


> ...But looking at a standard mini jack to stereo pair 1/4inch jack it docent seem to be shielded. ...


 
They're most definitely shielded. For all intents and purposes, they are two separate cables until they are joined at the mini jack. Usually you can even peel them apart all the way down to the mini jack.


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## bishopthomas (Dec 13, 2011)

waynehoskins said:


> I'm curious, is is sum-and-difference stereo like we use in stereo FM, or is it two discrete full-bandwidth channels?


 
It's 1's and 0's.


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## museav (Dec 13, 2011)

waynehoskins said:


> That was one of my first thoughts. I'm curious, is is sum-and-difference stereo like we use in stereo FM, or is it two discrete full-bandwidth channels? I had thought of using AES for interconnection between two digital consoles on a show I'm working on now, to send two unrelated channels from console 1 to console 2, and bringing back four unrelated channels from console 2 to console 1. It never came to pass since console 2 doesn't have AES outputs like I thought it would, so we are incurring the excess A/D and D/A conversions I hoped to avoid.


Technically, AES3 or AES/EBU is two channels of PCM digital audio, not necessarily stereo. So it is indeed two discrete channels. I have used AES3 between a number of different devices in order to keep the signal in the digital domain and avoid format conversions or the additional latency you noted.


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## waynehoskins (Dec 13, 2011)

bishopthomas said:


> It's 1's and 0's.


 
Well yes, but I was thinking about the data. I could see, for stereo uses, using sum-and-difference technique in the data to encode and reconstruct Left and Right, under the presumption they're related, that most of the information would be common to both channels. If the two channels were unrelated, there would be more crosstalk and artifacts since each one would have to be built from their sum and difference, the difference signal probably being lower-fidelity than the main channel if they took their cues from multiplex stereo.

It doesn't make much sense to do this with digital audio since there isn't, as far as I know, a bandwidth problem to overcome as there was with stereo radio transmission.

And edit: I clearly typed this too slowly, as Brad provided the answer while I typed.


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## FMEng (Dec 14, 2011)

waynehoskins said:


> Well yes, but I was thinking about the data. I could see, for stereo uses, using sum-and-difference technique in the data to encode and reconstruct Left and Right, under the presumption they're related, that most of the information would be common to both channels. If the two channels were unrelated, there would be more crosstalk and artifacts since each one would have to be built from their sum and difference, the difference signal probably being lower-fidelity than the main channel if they took their cues from multiplex stereo.
> 
> It doesn't make much sense to do this with digital audio since there isn't, as far as I know, a bandwidth problem to overcome as there was with stereo radio transmission.
> 
> And edit: I clearly typed this too slowly, as Brad provided the answer while I typed.


 
Stereo multiplexing just isn't worth the effort to save a pair of wires. Wire is cheap, but multiplexing isn't. Doing it in the analog domain doesn't yield very good crosstalk specs. We used to be overjoyed if an analog stereo generator made -40 dB crosstalk at 15 kHz. Performance is much better doing it in the digital domain, but the cost of the hardware is pretty steep.


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