i'm legitimately confused about balanced/unbalanced

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treymonfauntre

treymonfauntre

Magic Bag Of Sounds
i was playing with one of those presonus tube pres and for outputs it has an xlr output that is balanced and a (presumably) trs output that is unbalanced. why would they do this? is this not a trs output and i might as well just plug an instrument cable into it? if its just a ts output you're losing like 6db aren't you? i don't understand why a preamp would even have that option
 
The unbalanced output is a TS output. In all likelihood, you lose more than 6 db, as the balanced output is likely at +4 and the unbalanced is -10.

They have both so the unit can interface with both balanced and unbalanced gear. Additionally, the unbalanced signal does not go through what ever they are using to balance the signal, either a transformer or an op amp of some kind.


Light

"Cowards can never be moral."
M.K. Gandhi
 
A second output from a pre is really useful with computer recording because you can monitor the signal outside of the box (zero latency).

For this purpose an unbalanced signal isn't really a big deal as it's not a part of your recording chain.
 
Light, will an unbalanced cable send a weaker (in terms of db) signal than a balanced cable?

Are all XLR cables balanced?
 
all xlr cables are balanced.

balanced cables will send a stronger signal
 
notbradsohner said:
all xlr cables are balanced.

balanced cables will send a stronger signal
Click to expand...

XLR cables are ONLY considered balanced if there is a balancing circuit on one end of a cable.

a cable is used just to send signal down it. it does not change the signal into balanced or unbalanced...your gear does that.

a balanced XLR cable will give you a stronger signal in the end because of the process that occurs in the balancing circuit on the end. the two signal traveling down the cable are put in phase and then added together doubling the signal giving you a 3dB or so increase
 
With most balanced circuits, it's not that you gain with the balanced connection, you don't lose. The signal is usually padded when it is split, so when it is added together at the other end, it is at it's original strength. Using an unbalanced connection in a balanced circuit, you lose half the signal.
 
balanced is hot cold and ground unbalanced is hot and ground (correct me if im wrong) balanced can send a stronger signal with low noise therefore can be used in long runs unlike an unbalanced signal.
 
Balanced/Unbalanced

Balanced is two wires acting in a push-pull configuration with a seperate ground.

Unbalanced is one wire that carries the signal and one ground wire.

Unbalanced cables can do decently long runs, I think it depends on the impedance as well. They do tend to pick up more hum and RFI.
 
Lets review:

1. The cable doesn't determine whether a signal is balanced or not. An xlr or trs can carry a balanced signal but the gear determines if it is balanced or not. TS cables can not carry a balanced signal.

2. Plugging an unbalaced cable into a balanced input will loose you 6db. Plugging an unbalanced cable into an unbalanced input will not.

3. We must not confuse the cable/connector with the signal it is carrying. Just because it is an xrl cable doesn't mean that the signal is low impedace, mic level, balanced, etc... The piece of equipment that the signal is coming from (and going) to determines all those.

4. Gain staging is key. Make sure you know the operating level (+4 or -10) of each piece of equipment you have. Know if it is balanced or not and make connections apporpriately. Connecting a +4 piece to a -10 piece is fine as long as you know that 0db on the +4 piece will reed +11 on the -10 piece.
 
treymonfauntre said:
i was playing with one of those presonus tube pres and for outputs it has an xlr output that is balanced and a (presumably) trs output that is unbalanced. why would they do this? is this not a trs output and i might as well just plug an instrument cable into it? if its just a ts output you're losing like 6db aren't you? i don't understand why a preamp would even have that option
Click to expand...

The balanced circuits are at the output/input of your equipment. After the balanced amp, all equipment is unbalanced. The balanced transmitting/ receiving amps have two inputs to an op amp. The op amp will simply amplify the *difference* in voltage between the two inputs. If a signal (like hum, radio interf. etc) gets induced on *both lines* at the same time then the op amp cancels the signals all together (hence the name "balanced")

A balanced input/output is not an indicator of quality at all in studio equipment. Some of the best equipment ever made had unbalanced in/outs. You will notice that all live equipment have balanced in/outs. In equipment designed for live audio work, balanced in/outs *are* an indicator of quality.I would pass on any live equipment that was not balanced as every designer knows it is necessary (and if they saved a few $ on that, what else did they scrimp on?) In a studio unbalanced is fine and actually better than balanced because if the unit is unbalanced there is no balance amp to go through (in balanced equipment, in and out are two amp stages that add noise/distortion/coloration etc.) Think about a signal chain of two balanced devices, that is 4 amp stages. Anyway, you get the picture. Balanced is better for long cable runs (live, studio where equipment is far away) and unbalanced is best for minimum signal path.
 
The kicker when going between balanced and unbalanced equipment is that your gain stages are all designed to work best (clean & quiet) within a certain range. When you have to make up the 6db loss, you risk pushing one of your gain stages out of its optimal range. Then you're adding analog component hiss to your signal.

I use both balanced and unbalnaced quite a bit as my mixing board has (get this) balanced inputs and unbalanced outputs (?), and the insert points are unbalanced as well. You just have to be vigillant listening for his. I usually make sure nothing is going to play back, crank the monitors, and solo each channel to see if any of them are louder than the rest. Then I hunt down the spot where the noise is being added and fix it.

Take care,
Chris
 
ok i think i got it now. i'm kind of annoyed now that i learn that my fostex vf16 has unbalanced inputs. but i reckon it won't be a problem really
 
What Farview said. First the statement above that all XLR cables are balanced is untrue. An XLR to TS cable is unbalanced, or more correctly, it carries an unbalanced signal. If you do plug an unbalanced unit into a balanced jack, you lose 6db or so. In the greater scheme of things, that is no big deal. If all your cable runs are under 30', it really doesn't matter that much.-Richie
 
Balanced basically means it is using a differential amplifier to amplify the signal. This allows the difference between the 2 signals to amplified, while noise that will be picked up equally (theroretically at least) on both lines will be rejected (hence the CMRR--common mode rejection ratio---specification). While this is an exellent way to reduce the noise in you system, it is no guarantee of sonic excellence.... :) In general balance equipment will be of higher quality than unbalanced.
 
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