Balanced/Unbalanced cables...?
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Ruahrc

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The title pretty much explains it- what is the difference? I have heard these terms several times now and also have seen balanced/unbalanced used in antenna discussions (Radio is another hobby of mine) but I can't for the life of me figure out what it means!

Ruahrc
 
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Orpheus

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basically, unbalanced is your normal cable.

balanced cables allows longer cable runs (20'+) without more interference.

in a simple unbalanced cable, there is only one conductor that carries the signal, and a shield that traps interference. the balanced has two conductors, one that carries a "hot" (+) signal, and one for "cold" (-)... one carries the exact opposite polarity of the other. upon receipt of the signals, the "-" signal is subtracted from the (+) signal, resulting in the cancelation of all signal that was common upon the two wires.... so in other words, most of the interference that makes it through the shield gets cancelled out.

but anyway... for most household uses, balanced connections are not necessary. there are even ultra-high-end cables that don't have shields... like Nordost, and Kimber Kable... including many DIY designs... which goes to show that interference really isn't that big of a problem in a normal hi-fi system.

...but there might be one advantage of a balanced cable of use to an audiophile: the ground (connected to the shield) is not part of the signal chain... thus ground loops are avoided, thus helping with humming in your equipment.

but for the most part, if all your equipment is properly grounded to the same outlet, balanced cables (originally developed for microphones) are little advantage to you.

hope this helps,
dean
 
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Dreamslacker

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Quote:

Originally posted by Orpheus

in a simple unbalanced cable, there is only one conductor that carries the signal, and a shield that traps interference. the balanced has two conductors, one that carries a "hot" (+) signal, and one for "cold" (-)... one carries the exact opposite polarity of the other. upon receipt of the signals, the "-" signal is subtracted from the (+) signal, resulting in the cancelation of all signal that was common upon the two wires.... so in other words, most of the interference that makes it through the shield gets cancelled out.


Wouldn't this be more like... voltage differential?
 
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Orpheus

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well, i dunno what "voltage differential" technically means... but if it means something like the difference in voltages between the two wires... yes... that's the same as subtraction.
 
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Quote:

Originally posted by Orpheus
well, i dunno what "voltage differential" technically means... but if it means something like the difference in voltages between the two wires... yes... that's the same as subtraction.


It's a method used in data transferring over cables in some computer peripherals (SCSI). Where the data is transmitted using twisted pairs of signal wires and taken to be the voltage difference (as opposed to high-low or on-off binary) between the 2 wires at the other end.

With the CRC and correction system, non-correctable data corruption due to EMI/RFI is not likely to occur within many years.
 
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Ruahrc

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but if the same audio signal is passing over the (+) and (-) lines, (with reversed polarity) wouldnt all the audio signal get cancelled out when the subtraction is done?

If I'm reading it correctly balanced cable has 2 sets of the same audio (or data) passing through the cable, one on the (+) wire and one on the (-) wire?

Ruahrc
 
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Orpheus

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no... when you subtract a negative number, that's the same as adding right? example: 1 - (-1) = 2. not 0.

so, with + on one conductor, and - on the other... you get:

hot - cold = 2 * hot (since cold = -hot)

get it?

so, the interference is cancelled out, but the signal is the sum of the absolute value of the voltage on each conductor.

but again, don't sweat it if your stuff doesn't have balanced outs... balanced lines have little advantage for most home audio setups where equipment is close together, and there aren't many cable being used. in a pro studio, this is different, cause many studios have more than 1 mile of cable being used in close proximity to each other... in that case, balanced lines can help a lot.

you can however reduce hum problems using the same type of cable balanced cables use, but in an unbalanced configuration:

to do this, connect the one conductor to the "hot" on both ends. then connect the other conductor to the ground on both ends. also, connect the shield to only one side, usually the side that's going to be connected to an output. this configuration is what is mistakingly called a "half-balanced" or "semi-balanced" cable. technically, it has nothing to do with balancing... but anyway... it does help with hum somewhat.
 
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gerG

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Orpheus is quite correct. kwkarth also wrote up an interesting description with pros and cons.

I personally prefer balanced cables, but not just for the sonic merits. I like the XLR connectors better than RCA. If you use any pro gear, it typically has XLR balanced connectors, and sometimes 1/4" unbalanced connectors in addition. Since most home gear still uses RCA unbalanced connectors, it is difficult assembling a system which uses balanced interconnects. Mix and match is possible, and not usually a problem since the pro stuff detects the signal and switched for balanced or unbalanced. I build my own cables for these setups (RCA to XLR). Another complication: balanced XLR connectors come in both genders, so you also have to have separate input and output cables.

There is one place where balanced cables make so much sense that it seems like a no-brainer. That would be in a car. Oddly enough I have never seen auto gear using balanced connectors and cables. I am looking to fix that oversight!


gerG
 
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Ruahrc

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aah, makes sense now. So instead of having like "+10" and "0" the signal is carried as "+5" and "-5". Ingenious.

Ruahrc

p.s. I'm not really having RFI/hum problems, I was just curious.
 
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