Monitor hookup

[Adam P]

No matter what a manual says, TRS=balanced, just as XLR=balanced. TS=unbalanced.

Not always. I have a console with unbalanced buss outputs on XLRs.

 

[RAK]

XLR is a balanced cable. It has 3 wires/pins. Pin 1 (the X) is the Ground, Pin 2 (L) is the Hot. Pin 3 (R) is the Cold. The Cold wire acts as a shield eliminating hum and other noise (from lights for example) that the cable can pick up.

This translates to a 1/4" TRS cable in this way. T(Tip)-Pin 2(Hot), R(Ring)-Pin 3(Cold), S(Sleeve)-Pin 1(Ground). Again it is the Ring connection which makes it balanced.

A 1/4" TS cable is Unbalanced because it only has T(Tip)-Pin 2(Hot), and S(Shield) Pin 1. Because it does not have the Cold wire, it is prone to picking up noise particularly over long distances.

So to clarify. TRS and XLR are "Balanced" cables, but if you hook a TRS cable into a jack that is only wired for unbalanced TS operation, then the Ring doesn't have it's own connection on the jack.

 

[Reggie]

So to clarify. TRS and XLR are "Balanced" cables, but if you hook a TRS cable into a jack that is only wired for unbalanced TS operation, then the Ring doesn't have it's own connection on the jack....

...and your signal is therefore unbalanced as it goes through the TRS cable in this example. I'm sure you understand all this quite well, but I just know there are some people reading this stuff that will go "Hmm, OK; as long as I use a TRS or XLR cable I am running a balanced signal." The balancing act is done inside the piece of gear; the cable is just simple wires and insulation carrying whatever signal you send through it.

 

[RAK]

My definition of a balanced cable is one that has three wires. A TRS cable has three wires so it's always a balanced cable no matter what it plugs in to. A jack may or may not accept a balanced plug, but the plug remains balanced.

I agree that people need to be aware that using a TRS plug doesn't mean you automatically have a balanced connectin if the jacks are not wired for balanced operation.

Also, in terms of XLR, there is no such thing as an unbalanced XLR jack. While 1/4" cables come in two versions, TRS and TS, XLR input/output jacks are by default balanced.

 

[Reggie]

I can wire you an unbalanced XLR jack if you like. It will carry an unbalanced signal over an unbalanced XLR cable if you like as well.

In my mind, cables are just wires. 2-conductor or single conductor. A signal is either balanced or unbalanced. I dunno, maybe I do have it wrong. I guess calling a cable balanced is an unrelated issue. Kind of a confusing classification though...

Sorry to keep picking, but I think this deserves some clarification.

 

[RAK]

Show me one piece of commercially made gear with an unbalanced XLR Connection?

The cable is what's balanced.

If I showed you a 1/4" TRS M to 1/4" TRS M cable, and I asked you, is this a balanced cable or an a unbalanced cable? what would your answer be? Are you saying a cable only becomes balanced or unbalanced once it's plugged in to something.

People talk about cables as balanced or unbalanced cables all the time, just as 1/4" Jacks (the female ends) are wired to accept a balanced and/or unbalanced cable.

A signal is a signal, carried over either a balanced or unbalanced cable. It's that third wire that makes the cable balanced, not the signal going through it.

 

[Reggie]

OK I understand that people say a cable is "balanced" or "unbalanced" based on the connectors; but I don't think they understand what they are saying. I'm telling you, the cable makes it possible to carry a balanced signal, but the cable does not do the balancing itself. It does not magically invert the polarity on the cold(-)/(XLR pin3)/(TRS ring) wire. The balancing is done inside microphones, or by op-amps and transformers in audio gear. A KSM32 does this with a transformerless circuit. A SM57 does this via transformer. They balance the signal, send it across some metal (a cable containing a twisted pair of wires--one carrying the +signal and the other carrying the reverse polarity signal--wrapped in a grounding shield), and the next piece of gear uses a differential amplifier or transformer to recombine the + and - signals while rejecting any interfering noise. Often times the signal runs unbalanced through the circuit and is balanced again at the output of the device by opamps or transformers.

Trying to find some references for you....this is the best I can do so far:

http://www.dplay.com/dv/balance/balance.html

You can't tell a wire by its connector.
Balanced wiring is sometimes called XLR wiring because it often uses that kind of three-pin connector. But it's dangerous to assume that an XLR plug or jack is balanced. Although most manufacturers reserve these connectors for balanced circuits, there are exceptions. Check the equipment specs.
You can also get into trouble assuming that other kinds of connectors aren't balanced. Some manufacturers save money and space by putting balanced signals on three-conductor phone jacks. From the front panel, these look identical to two-conductor unbalanced jacks. But if you connect a three-conductor phone plug -- also known as Tip-Ring-Sleeve, or TRS -- it can carry a balanced signal. Again, check the specs.

And a balanced connection works only if both ends are balanced. If either of the two internal wires are shorted to ground at either end, the whole thing becomes unbalanced. This can happen easily if:

You plug one end into an unbalanced circuit
You use most kinds of XLR-to-Phone or -RCA adapters
The cable is damaged

 

[RAK]

I understand all that, and I'm with you. People should understand the difference between a balanced signal, and an unbalanced signal, but I think refering to cables as balanced or unbalanced is here to stay. But you're correct, people need to understand if they plug a TRS cable into a jack that isn't wired for balanced operation, they're not getting a balanced signal.

I just recently found out that both pronunciations of "timbre" are actually correct. Imagine that? I think I'll still always pronounce it like "tambor" though.

 

[Reggie]

Fair enough. You just had me worried that we were regressing further with this statement:

A signal is a signal, carried over either a balanced or unbalanced cable. It's that third wire that makes the cable balanced, not the signal going through it.

In my mind I pronounce it "Timber!" but I try to avoid the word as much as possible because I know most people pronounce it "tambor", and I just don't trust a word that sketchy.

 

[Adam P]

Show me one piece of commercially made gear with an unbalanced XLR Connection?

Would you like to see the block diagram as well?

 

[gordone]

OK, my Great River MP2 has unbalanced outputs via an XLR connection.

Show me one piece of commercially made gear with an unbalanced XLR Connection?

 

[gordone]

WRONG! See my post on the Great River MP2. Do you really work for Shure?

Also, in terms of XLR, there is no such thing as an unbalanced XLR jack. While 1/4" cables come in two versions, TRS and TS, XLR input/output jacks are by default balanced.

 

[gordone]

My answer would be "It is a TRS cable, capable of carrying TWO signals"
These two signals can be the two that make up a single balanced signal, OR two unbalanced signals (ala stereo)
So you're saying since my Sony headphones have a TRS cable on the end, they must be balanced?

If I showed you a 1/4" TRS M to 1/4" TRS M cable, and I asked you, is this a balanced cable or an a unbalanced cable? what would your answer be? Are you saying a cable only becomes balanced or unbalanced once it's plugged in to something.

 

[RAK]

Would you like to see the block diagram as well?

Well, actually that picture doesn't really show me anything. I've used an A&H GL series, but don't know that board.

 

[RAK]

WRONG! See my post on the Great River MP2. Do you really work for Shure?

I'm sorry, but I'm not familiar with a Great River MP2. And yes, I currently work for Shure.

 

[RAK]

My answer would be "It is a TRS cable, capable of carrying TWO signals"
These two signals can be the two that make up a single balanced signal, OR two unbalanced signals (ala stereo)
So you're saying since my Sony headphones have a TRS cable on the end, they must be balanced?

That's absolutely correct, but I wasn't trying to confuse the situation any more.

Yes your Sony headphones with the TRS cable on the end would be called a Stereo cable, and it does not send a balanced signal. Same as an Insert cable is not balanced because it also sends/returns a signal.

Of course there are headphones that do work on balanced operation, but that's an entirely different story.

So it works like this then: if a TRS cable carries a mono signal it's balanced, and if it carries a stereo signal it's unbalanced.

I was just trying to stick to dealing with mono signals over a TRS versus TS cable. Make sense?

Also, there are excellent explanations on wikipedia about balanced audio, if anyone wants to read up on it.


Also, here's a quote from Wikipedia about XLR. I think we can assume you know I was only refering to 3-pin XLR used for audio, and not DMX or Clear-Com type connections.

"The most common is the 3-pin XLR3, used almost universally as a balanced audio connector for high quality microphones and connections between equipment."

So obviously "almost univerally" does allow some room for something else, but not really even work mentioning I would think.

 

[gordone]

http://mercenary.com/greatrivel4c.html, the MP2 is the same but 2 channels and unbalanced outputs (via XLR jacks! ). I paid around $1200 for mine back in 2000.

The MPX series are Great River's "clean" preamps, most folks usually talk about their MP2NV, which is their more "colored" pre. Since I do folk/acoustic stuff, I wanted "clean" . I have short cable runs, so I didn't need the balanced outputs.

I'm sorry, but I'm not familiar with a Great River MP2. And yes, I currently work for Shure.

 

[RAK]

http://mercenary.com/greatrivel4c.html, the MP2 is the same but 2 channels and unbalanced outputs (via XLR jacks! ). I paid around $1200 for mine back in 2000.

The MPX series are Great River's "clean" preamps, most folks usually talk about their MP2NV, which is their more "colored" pre. Since I do folk/acoustic stuff, I wanted "clean" . I have short cable runs, so I didn't need the balanced outputs.

I copied some of the specs you sent from the link.
This is the MP-2M:
O U T P U T S
MP-2M

Type: balanced (unbalanced optional, call)
3 Pin XLR connector on rear panel
(XLR pin 2 is hot)


So obviously the standard is balanced operation, and the other models on that page operate with standard XLR operation. Yes, it's true I wasn't aware there was unbalanced XLR wiring in commercially available products (of course I knew you could do it), but it's clear it's no where near mainstream or standard, since you even have to call to get unbalanced operation on this box. Particularly with people just starting out in home recording, it's not worth the confusion. Any box they're going to buy is going to be wired for balanced XLR connections. Also, see my edit to my post before this about the same isssue from Wikipedia.

 

[Reggie]

So it works like this then: if a TRS cable carries a mono signal it's balanced, and if it carries a stereo signal it's unbalanced.

See, I think we are on the same page, and then you say something like this. I still don't think you understand the fact that a cable does nothing to balance a signal. You gotta have guts of some kind to do the balancing - opamps, transformers, etc. A TRS cable can no doubt carry a mono unbalanced signal. I also use a TRS patchbay to route mono unbalanced signals. If the ring or XLR pin3 is getting routed to ground, then like it or not you are running unbalanced.

So I have taken the liberty of rephrasing your statement for you:

So it works like this then: A TRS cable is capable of carrying a balanced mono signal, an unbalanced mono signal, or an unbalanced stereo signal.

 

[RAK]

Look, I don't wnat to get into a thing here. I do understand what you're saying, you really want to argue over words here?
I said "if a TRS cable carries a mono signal" Clearly, if the cable carries this signal, then it is capable of carrying the signal, because it is carrying the signal.

From the "Balanced Audio" entry on Wikipedia.

A balanced audio connection has two wires, one of inverted polarity to the other. (For instance, in an XLR connector, pin 2 carries the signal with normal polarity, and pin 3 carries an upside-down version of the same signal.) However, an XLR plug also carries a third connection - pin 1 is used as an earth to shield the other two. The received signal is the difference between the two signal lines. This signal recombination can be implemented with a differential amplifier where the negated signal is tied to the negative terminal of the operational amplifier. A balun may also be used instead of an active differential amplifier device. Much of the noise induced in the cable is induced equally in both signal lines, so this noise can be easily rejected - the noise received in the second, negated line is applied against the first, upright signal, and cancelled out when the two signals are added together.

The separate shield of a balanced audio connection also yields a noise rejection advantage over a typical two-conductor arrangement such as used on domestic hi-fi where the shield is actually one of the two signal wires and is not really a shield at all, but relies on its low, but in practice not zero, impedance to signal ground. Any noise currents induced into a balanced audio shield will not therefore be directly modulated onto the signal, whereas in a two-conductor system they will be. This also prevents ground loops.

All that makes sense to may, and always has. Whatever it means to you, that's wonderful too.