balanced vs unbalanced

Jim Brennan

Jim Brennan

VHS Member Old Skool
no, I don't mean my mental state.

Just wondering what a balanced XLR connection does that 1/4" unbalanced jack doesn't.


I may have to use a mixer that has 1/4" jacks for output, so I was going to get adapters to run my XLRs to the camera. What will that do to the signal?
 
Jim Brennan said:
no, I don't mean my mental state.

Just wondering what a balanced XLR connection does that 1/4" unbalanced jack doesn't.


I may have to use a mixer that has 1/4" jacks for output, so I was going to get adapters to run my XLRs to the camera. What will that do to the signal?
Click to expand...

For a short cable run, nothing. A balanced input carries a "reversed" signal of source so that interferences can be can be canceled out. This allows balanced XLR cable to go for hundreds of feed. An unbalanced cable can go maybe ten feet at the most; any longer and you will pick up intereferences.
 
jade8472 said:
For a short cable run, nothing. A balanced input carries a "reversed" signal of source so that interferences can be can be canceled out. This allows balanced XLR cable to go for hundreds of feed. An unbalanced cable can go maybe ten feet at the most; any longer and you will pick up intereferences.
Click to expand...

Okay, so if I am using an XLR cable from the camera (say 25 feet), then run that into an xlr to 1/4" adapter at the mixer I should be okay, right? Or does adding that adapter and running it into the 1/4" jack at that end effectively remove the benefit of the XLR?
 
Yeah it does. Any time you directly "un-balance" a cable at any point without an active peice of gear or an isolation transformer, you will unbalance the whole line.

- Mikko
 
Generally a balanced XLR mic path is low impedance and a 1/4" path is high impedance. This involves not just the cable itself, but the mic and the I/O circuitry at each end as well. Probably the biggest benefit of all that is the ability of a balanced Lo-Z (Z = impedance) circuit to run much longer distances than its Hi-Z counterpart *without high frequency loss*. It will sometimes be quieter as well, but well managed Hi-Z paths can be just as quiet. They're a little less forgiving where RF (radio frequency) interference and such is concerned, but Lo-Z mics/cables are also fully capable of picking up radio stations, taxi CBs and so on though, if the signal is strong enough, so Lo-Z is no guarantee of interference-free performance.

A decent quality (but not necessarily "high-end") Lo-Z mic cable can run about 300 feet with no significant loss in HF response. A similar Hi-Z run will begin to lose HF beyond 30 feet or so. For some sources, like electric guitars for example, it's acceptable to go up to about 50' because they (and their corresponding amps) don't produce much meaningful frequency response above 8-10 KHz or so. For a high quality condenser mic and a human voice though, it's another story.

Regarding adapters, it's true that if you simply attach a simple XLR to 1/4" adapter at the end you would lose the Lo-Z benefit because you decoupled one end of the transformer-balanced line. The adapter just rewires the connector to enable it to "talk" to Hi-Z.

However, if you were to attach a proper, transformer-equipped Lo-Z to Hi-Z adapter (aka "direct box", although some are simple inline-style modules), you should be fine because only the 1/4" connector (and what it's plugged into) would be operating at Hi-Z. Your entire cable run from the mic to the adapter would still be balanced Lo-Z.

Radio Shack makes perfectly serviceable inline Hi-Z/Lo-Z transformer-equipped XLR-to-1/4" adapters of both genders for about $12. I have several of them and use them often in my recording studio, although incidentally almost never with long cable runs.

A direct box may cost you a few db of signal level, depending on the design, but that is usually easily made up for with a little extra preamp gain.

Disclaimer: I'm a professional recordiing engineer, but not an EE (Electrical Engineer, which involves specific academic training and certification in just these kinds of subjects). I will stand corrected on any of this if someone more expert than I in the intricacies of circuit design chooses to do so.
 
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Thank you Ted! You just helped me out :)

I wasn't sure about attaching a XLR to 1/4 adapter, but I'll look into those Radio Shack ones.
 
So, for a 25' XLR cable, (using an XLR to 1/4" adapter) running from the 1/4" line out on a powered mixer to my camera, I might be okay?

can the same be said for a 25' cable running from a boom mic to a 1/4" input trhough the same adapter?

Disclaimer: I am not an electrical engineer or a recording engineer. I'm just an idiot with a camera trying to figure all this out :beer:
 
I think the frequency response makes a difference over the longer distances, so it might depend on what you are miking. But I need this for doing interviews.
 
Jim Brennan said:
So, for a 25' XLR cable, (using an XLR to 1/4" adapter) running from the 1/4" line out on a powered mixer to my camera, I might be okay?

can the same be said for a 25' cable running from a boom mic to a 1/4" input trhough the same adapter?

Disclaimer: I am not an electrical engineer or a recording engineer. I'm just an idiot with a camera trying to figure all this out :beer:
Click to expand...

Jim the answer is yes, as long as in each case you are using the proper adapter ( an adapter with a transformer) and you are connecting a line level input to another line level input ( or mic level to mic level whatever the case).

One thing to keep in mind that may not be obvious. Some/Many audio devices that have 1/4" jacks are in fact balanced. I would generalize and say that lower end devices tend to only be unbalanced, while higher end devices are usually balanced or have both. You just need to read the device or the manual to know. A balanced 1/4" jack is TRS (tip ring sleeve) unlike the standard TS (tip sleeve) jack. A balanced 1/4" and an XLR are electrically identical and can be connected with a simple cable that does not require a transformer.

For example, in my studio, I have 32 XLR patch points out in the rooms (balanced cables) that are wired into a 1/4" balanced patch bay in the control room. In case you are wondering, yes that is a lot of soldering! If I have a piece of unbalanced gear out in the room, like a guitar or a synth or whatever, I run it thru this which essentially a fancy version of the $12 Radio Shack adapter.

Hope that helps and does not make things less clear :)





FWIW, it is quite common to use balanced cable runs that are 1000's of feet long in situations like concerts with very minimal loss. The same would not be true for unbalanced.
 
Thanks! That info helps. After reading my manual I found that my 1/4" line in jacks are balanced, but my line out jacks are not. So an adapter with a transformer would only be necessary for the line out, correct?

It appears the aforementioned Radio Shack adapters fit that bill, no?

I feel like less of an idiot now. I love this site!
 
Jim Brennan said:
So, for a 25' XLR cable, (using an XLR to 1/4" adapter) running from the 1/4" line out on a powered mixer to my camera, I might be okay?

can the same be said for a 25' cable running from a boom mic to a 1/4" input trhough the same adapter?
Click to expand...

Probably yes for the line signal. The 1/4" adapter end does need to be correctly wired for best results (although I forget right now exactly what pins solder to what). If it's done the wrong way it may still work but you could get muddy sound and low level.

The mic, assuming it's Lo-Z (which is almost a certainty) may be another story. Depending on its exact impedance and that of the input dedvice, it may perform OK or it may not. A mic is a much less forgiving thing than a line signal is where this kind of mismatching is concerned. I'd highly recommend at least a simple Hi-Z-LoZ transformer adapter like the Radio Shack one for that.

I suggest you try the rig out beforehand if at all possible, and listen to the results on a decent playback system to be sure.

Best of luck.
 
Not sure what soldering you are talking about (I solder about as good as I dance). I was going to see if I could find a male/male xlr to 1/4" adapter for the line out. Do they make those?

I have a pair of Female XLR to male 1/4" adapters from radio shack to use for the mics.
 
tigeba said:
One thing to keep in mind that may not be obvious. Some/Many audio devices that have 1/4" jacks are in fact balanced. I would generalize and say that lower end devices tend to only be unbalanced, while higher end devices are usually balanced or have both. You just need to read the device or the manual to know. A balanced 1/4" jack is TRS (tip ring sleeve) unlike the standard TS (tip sleeve) jack. A balanced 1/4" and an XLR are electrically identical and can be connected with a simple cable that does not require a transformer.
Click to expand...

Correct.

And as you pointed out, one way to spot a balanced 1/4" connector is that it has three conducting surfaces: the tip, a narrow middle "ring" and sleeve, or ground. It looks exactly like a 1/4" stereo headphone plug, or for that matter, any stereo 1/4" connector, which is where you need, again as you pointed out, to read the manual for the devices in question. Their specifications wll indicate whrther the circuit is balanced or not.

You might find stereo 1/4" connectors that are wired to a mono device (they work just as well that way), so check carefully. The connectors are not the definitive indicator.
 
Jim Brennan said:
Not sure what soldering you are talking about (I solder about as good as I dance).
Click to expand...

I'm a crappy dancer, but I can solder like a champ. If there's ever a dance step called "the wireman" I'll be rockin' : )

What I was referring to is the way an unbalanced (2 conductor) cable is wired to a 3 conductor (balanced) XLR connector. IIRC, the unbalanced ground wire goes to pin 1 on the XLR and the hot wire goes to pin 2. Optional is whether the ground wire is also connected to the ground (pin 3). Depending on the device(s) in question, it may be preferable to do one or the other. I find that the first way I described is usually best. It is advisable to check store-bought straight-wire (non transformer balanced) 1/4" to XLR adapters regarding this distinction.

I was going to see if I could find a male/male xlr to 1/4" adapter for the line out. Do they make those?
Click to expand...

I don't recall seeing one of those, but a combination of a M-F and a M-M of either category would do the same job. Not so cool if you've got it stuck in the side of a camcorder though - the total length of it all could get a bit out of hand.

I have a pair of Female XLR to male 1/4" adapters from radio shack to use for the mics.
Click to expand...

If they're transformer balanced, like the Radio Shack ones here:

http://www.radioshack.com/product/i...=xlr+adapter&kw=xlr+adapter&parentPage=search

and here:

http://www.radioshack.com/product/i...=xlr+adapter&kw=xlr+adapter&parentPage=search

Then you're good to go.

If they're not, like this (which incidentally includes a cable):

http://www.radioshack.com/product/i...=xlr+adapter&kw=xlr+adapter&parentPage=search

Then you will probably have problems with a mic level signal.

By the way, it's been too long since I checked Radio Shack's prices - the transformer equipped XLR to 1/4" adapters have gone up to a whopping $15 for the 1/4" F to XLR M, and $16 for the other gender. Still a steal though : )
 
THe ones I have are definitely rhr ones with transformers then. As for the male/male xlr to 1/4", that will be coming out of the powered mixer. Nothing but XLR cables going to the camera.

Thanks again.
 
OK, wait a minute.

Most mixers thee days have "smart" 1/4" jacks. They are both TRS (Tip, Ring, Sleeve) and TS.

Try using a TRS Male to XLR Male to connect the mixer to the camera. That way you preserve the balanced connection and all of its benefits.

Regards,

Ty Ford

(actually I'm a federally licensed engineer, but given the state of the federal government -- The FCC in particular -- that ain't sayin' much.)
 
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