what's the difference between a balanced and an unblanced out?

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ad0lescnts

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Pardon my complete ignorance....i have a preamp and it has the option of a balanced XLR out and an unblanced 1/4" out and i'd like to know the difference. Thanks a lot

Tyler
 
I'm kinda drunk, so this isn't gonna be long...

To make it short, balanced is a stereo 1/4" or an XLR cable...running a mono signal. There's a phase change that goes on in the signal path that cuts out all of the noise that would occur had you not been running balanced.

Really, just make sure that if you're going to run cables longer than 20 feet, use all XLR or 1/4" stereo cables for everything...I hope this makes sense, I'll try to post more tomorrow when I'm in good health!

You can do some searches on the difference between balanced and unbalanced and probably get a really detailed description of what is what.

I hope this helps at least a little...

Darth
 
awwwwwww man thanks a lot it helps.. i'm still kinda shaky on it but it clears up a lot. thanks a lot

Tyler
 
Lets try to explain this in a simple matter:

balanced cables send the signal trough 2 signal wires.
In the beginning of the cable these two different wires are put out of phase, at the end of the cable the two wires are being put into phase again. Any hum or buzz that's picked up on the way will be affecting both the wires. At the end of the wire the original signal is set back in phase, and the hum and buzz out of phase resulting in cancelation.

If a signal is totally out of phase it's cancelled. So if you would listen to the original signal half way the cable it wouldn't be there (remenber its being put out of phase), any hum and buzz will be there (it's picked up half way by the cable, and affects both wires the same resulting in phase buzz and hum.)
At the end the phase of one wire is reversed in phase, resulting that the signal is in phase again, and the buz and hum out of phase.

Unbalanced cables send all the hum and buz picked up on the way through. Its not filtered out at the end.

There is also a 14dB difference between the two.
unbalanced operate at -10dB
blanaced operate at +4dB
 
downside

my alesis 3630( please, no one start im not in the mood!) has a
-10db & +4db switch for output , is this by anyway giving me the option for bal or unbal?
 
Sorry Dowside... you were doing ok until the end, where you mixed signal gain structure into it....

Balanced/Unbalanced connections are one concept... gain structure (or signal strength) is a completely separate issue.

You can have unbalanced signals running +4dbu and balanced signals running -10dbV....... it is just more common to have balanced runs AND a high gain structure.

In addition, the difference in db between a -10dbV signal and a +4dbu signal IS NOT 14 db, it about 12db (actually11.80db)....

plug the number into this equation:
Difference in dB = 20 * (LOG(measured voltage/reference voltage))

The reference voltage for a -10 dbV signal is 0.316Vrms, and for a +4 dbu signal is 1.23Vrms.

Bruce
 
thanks blue bear

i was getting as little confused for minute.
 
Blue Bear, thanks for correcting me about that. Theory has never been my strongest talent.
 
I was drunk, but I kinda got the point accross! I was actually surprised when I read it again and it kind of made a little sense!

Darth
 
The concept at work is common mode rejection, and some input stages are better at it than others. When you evaluate a piece of gear and look at the specs, CMRR, common mode rejection ratio, will tell you how well the balanced inputs will reject noise. Do understand though, that it is only noise that is induced into the cable that is rejected, not source noise. Source noise will be back in phase when summed.
Cheers, RD
 
Correct me if I'm wrong but I thought that the balanced cable did not really have much to do with elimating noise. (It helps to prevent noise). The noise rejection or common mode rejection happens at the input. This property is caused by op-amps at the cable input, but not the cable itself. The op-amp will amplify any difference between the signals in the wires and cancel out and common portion of the signals, hence common mode rejetcion ratio
 
You are confusing me. I am at the edge of being really drunk. From my point of view at this moment Robert is right and Maxwell is bull. Sorry Max, it probably is the beer, but ....fuck.
 
maxwell said:
Correct me if I'm wrong but I thought that the balanced cable did not really have much to do with elimating noise. (It helps to prevent noise). The noise rejection or common mode rejection happens at the input. This property is caused by op-amps at the cable input, but not the cable itself. The op-amp will amplify any difference between the signals in the wires and cancel out and common portion of the signals, hence common mode rejetcion ratio
Click to expand...
Balanced runs eliminate noise induced into the signal as it passes through the cable.... it's not the cable itself that's doing it - it occurs at the inputs when the 2 out-of-phase signals are recombined. It only applies to induced noise, not noise already present in the signal before being sent thru the balanced line............

Bruce
 
Yeah Bear,

That's what I was trying to say. Sometimes it is hard to get your point across when your typing instead of talking face to face
 
I think both you and Robert were saying it - just not the same way! ;)

Bruce
 
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