Balanced/unbalanced lines?

[jethani]

Hi Gang.

I'm taking a class on Audio Engineering at the moment, and I'm getting pretty lost in all the discussion surrounding balanced and unbalanced lines. Bear in mind that my knowledge of electricity can be summed up in the phrase: it hurts.

I don't what makes one kind of line balanced or unbalanced; if one kind is preferrable to the other; why such discussions almost always concern 1/4" jacks; and why it seems to be affected by whether you plug the 1/4" cable all the way in the plug or only part of the way.

And what's a ground? This is usually cited as being something different from the positive and negative signals...help!!

Please explain it like I'm 4.

Always in Awe of the Knowledge in this Room,
jethani

[Emeric]

Hey Jethani,

Tough to explain like your 4, kind of a technical question... however

>I don't what makes one kind of line balanced or unbalanced;>

A balanced line consists of 2 conducters, positive (non-inverted) and negative(inverted) as well as a braided shield for...shielding interference. So, two signals are send down the two wires of the cable, but are out of phase with one another (180 degrees, this is important).

With an unbalanced line, there is only a single wire carrying the signal sent down the cable, with ground as the signal return.

<if one kind is preferrable to the other; >

Balanced lines are preferred because the cool thing is, once these two signals are combined at the input of your mixer, any noise that was picked up along the way is cancelled out, and you end up with the original signal.

<<why such discussions almost always concern 1/4" ..>>

The 1/4" cables that plug in half the way or all the way are TRS cables (tip ring sleeve). This type of cable and jack is often used to hook up an effect unit to a particuliar channel on the mixing board. These are plugged into the Insert jack of the mixer. For example, plug in the cable all the way, and hook the 2 1/4" plugs on the other end into the send and return of your... compressor, reverb.. whatever. Plugged in halfway this acts as just an output - to your multitrack or... etc.

So this TRS cable has 2 wires and a shield. And yes it can also be used as a balanced cable, with other balanced devices that use 1/4" balanced connectors.

Ground relates to unbalanced cables, which uses the earth as it's return. Unbalanced cables are isolated from the ground.

Sorry to ramble on.. there have been a few technical questions on here lately and I've been getting back into this kind of thing (electronics).

I'd be happy to elaborate on any of this if you have any other questions.

Emeric

[Conrad Josepi]

Emeric!

Please help me out here. I've never understood how an insert could be of any use, because there's only one 1/4" jack.

you say:

<<The 1/4" cables that plug in half the way or all the way are TRS cables (tip ring sleeve). This type of cable and jack is often used to hook up an effect unit to a particuliar channel on the mixing board. These are plugged into the Insert jack of the mixer. For example, plug in the cable all the way, and hook the 2 1/4" plugs on the other end into the send and return of your... compressor, reverb.. whatever. Plugged in halfway this acts as just an output - to your multitrack or... etc.>>

Are you saying that ONE 1/4" connection can be used as a send AND return of a signal?

Or is this a special cable that has (1) 1/4" jack on one end and (2) 1/4" jacks on the other.

Can you give me a specific example?

I appreciate any input!

Conrad Josepi

[Matt]

. . . And what happens if you use balanced cables with unbalanced equipment?

[Emeric]

Conrad,


Yes one cable can if it is TSR. These are special cables, and you can use them to send and receive. Your mixer of course has to have inserts.

You can use a normal 1/4" to 1/4" cable if you want to send an input signal OUT of your mixing board inserts INTO your multitrack. Plugged in halfway. (not shouting.. just emphasizing )

Or you can use the TSR cable that is basically a stereo plug that is meant for inserting a processing unit, compressor, reverb..etc. inline with that channel. Plugged in all the way.

A specific example: I have 1 mic coming into channels 1 of my mixer. Channel 1 is a kick drum. I plug the 1/4" stereo male into channel one (all the way) and plug the ends of that (the two 1/4" send and receive's) into my compressor input and output accordingly. This will compress just that channel.

I guess the overall thing is that inserts work better for some signal processing than other methods (AUX, effects send etc.), and they are great for organizing your multitrack setup.

Emeric

[Dragon]

Conrad, you've seen this technology before, you just didn't know it: on every stereo headphone plug you've ever looked at!

Matt, properly designed balanced equipment can use unbalanced cables to hook to unbalanced equipment with no problem, although the noise reduction will of course not be operating (balanced lines are mostly intended and important for mics). Unbalanced equipment just doesn't "see" the balanced lines...like using a stereo cable for a mono hookup.

Emeric...thanks, you did a great job on a tough subject!

Youse guyz might also want to check out
http://homerecording.com/ubb/Forum3/HTML/000358.html
http://homerecording.com/ubb/Forum3/HTML/000371.html

...and the FAQs.

[Conrad Josepi]

You guys/gals ROCK!

You've opened up a whole new world of possibilities!

My Layla card was just delivered here at work. Now, I have to wait until 5:00......

Conrad Josepi

[Conrad Josepi]

One more question:

I am in the process of ordering cables for the connection between my Mackie mixer and the Layla input card.

What type of cables should I order?

Normal 1/4" cables?

It is just being used to transport my preamped mic signals from the Mackie to the Layla.

I am assuming that I dont need the TRS.

Conrad Josepi

[Conrad Josepi]

I am grateful for your explanation! I almost have it.

I'm still confused about one thing.

Your specific example (Emeric) says
<<: I have 1 mic coming into channels 1 of my mixer. Channel 1 is a kick drum. I plug the 1/4" stereo male into channel one (all the way) and plug the ends of that (the two 1/4" send and receive's) into my compressor input and output accordingly. This will compress just that channel.>>>


Is this a Y-cable? are there two plugs on one end and one on the other?

Conrad Josepi

[Dragon]

See, Conrad, you're getting it! You can almost picture it in your mind now...for the rest of us, an insert cable has a 1/4" stereo plug on one end, and each of its circuits is wired to a separate 1/4" mono plug at the other end in a "Y" configuration.

[Howlin]

Let me get this straight:

For adding effects to a single channel -- You plug the stereo jack of a Y cable past the first click into a mixer insert, and plug the two mono jacks into the input and output (L/mono) of a processor. The mixer uses the tip and ring connections to send the signal to a processor and receive the altered signal, then sends the altered signal to the main mix.

For recording -- You use a mono cable with one jack at each end, plug it half-way into the mixer's insert to the first click, and plug it into a line-in on a recorder. The tip connection sends the channel signal to the recorder.

If you have a processor with L/R sends, can you plug a mono cable from the R output to a second channel? Will it act as a splitter and send the input signal from the first channel to the second? Suppose I have a guitar miced to the first channel and I want to add chorus to it, but I want to make it sweep left to right; I need two tracks of guitar, centered with the effect L/R... I just bottlenecked my brain. There must be something simple that slips my mind.

[Emeric]

Hi Howlin,

I'm not sure if understand, but if you want to do a stereo thing with your stereo effect unit there are a few options.

1. Use your Stereo FX sends and returns on your mixer.

2. Using a straight 1/4" to 1/4" mono cable. Plug it in to the first click on the insert. Plug the other end into the input of your FX unit. Plug the two outputs of your FX unit into the inputs of a spare set of channels. This is good cause you can pan hard left and right and EQ etc the effect itself. You can mix a bit of the stereo effect in with the dry signal, or bring up the FX faders at a certain point with some wild phaser or what ever your into.

If this is something you want to do while your recording, as opposed to mixing down, you will need to use up two tracks of your multirecorder setup.

Emeric

[Howlin]

Thanks, Emeric

Number 2 clears things up. (That's not a pretty sentence, is it.) I don't know why I was thinking of bringing the effect back to the mixer instead of out to the recorder.

[jethani]

Hi Gang.

Sorry I've not piped-in since posting the original message, but I've been studying for an audio engineering exam these past few days. (Went very nicely, happy to say!)

Thanks to all who posted replies & added their own questions. Here's a synopsis of what I've learned about balanced and unbalanced lines--

1. Balanced lines are nearly always preferable to unbalanced lines if only for their significant noise reduction,

2. You can route the signal path from your console to either your multitrack or effects devices using balanced lines by plugging them in all the way-- both on the console AND the multitrack/effects units,

3. ...UNLESS you are trying to achieve a stereo return from an effects processor, in which case you only insert the TRS up to the first click on the channel out on the console, then plug the other single end of the straight 1/4" to 1/4" cable all the way into the input jack on the fx unit. Use a separate cable to send two output signals (R + L) from the fx unit to two unused tracks on the console, panning one hard L and one hard R, thereby creating your stereo field.

I'm still kinda unclear about the ground signal in an unbalanced line (again, I have *no* knowledge of electricity). I'd like to dabble into soldering my own cables in the near future; can anyone explain this concept?

Also, if balanced lines have the distinct advantage of cutting down on noise entering the signal path, shouldn't *all* lines coming into the console be balanced? How do RCA cables come in? (My old Fostex board employs a lot of these kinds of jacks)

You guys are great; I feel much more familiar with this topic now.

jethani

[Emeric]

Hey Jethani,

1. yes, pretty much.

2. Yes, assuming these are balanced line out's (not inserts) when sending it to your multitracker as well as balanced in's on your FX and multitrack. The insert is for inserting a processor in line with a channel.

3. Yes, this is one way when using inserts. They are an output as well as an input but different than channel out's (which can be balanced or unbalanced). - different output connector.

Ground is the common return line for all unbalanced equipment, unbalanced lines only have 1 signal conductor. The tip is hot and ground is the braided shield.

Other instruments, electric guitars, bass, keyboards, are unbalanced. So you can't eliminate unbalanced totally.

Glad your test went well.

Emeric

Oh yeah, RCA only have 2 wires, signal and ground, - so - Unbalanced.



[This message has been edited by Emeric (edited 06-26-1999).]

[Dragon]

Just to clarify one or two little tidbits...

Ah, if we could only go back in time! Then all guitar and mic, and perhaps other cables would all be balanced, but where would the manufacturers of de-hissers be?

It's mostly equipment that puts out low-level signals (like mics and guitars) that should be balanced, because these things need a lot of gain/amplification to get their signals to where we like to work wih them, and it's actually the gain that picks up the noise. That's why line-level signals aren't as susceptible to noise, so they're usually not balanced unless there's a long run back to the mixer (check out stage snakes one day if you ever get a chance).

On normal unbalanced cables, the ground wire is usually braided, to make a kind of Faraday cage around the hot lead, which blocks a lot of the noise. Don't ask me about Faraday cages unless you want to hear a lot about radio waves!

P.S. Since Jethani started this topic with a joke, I'm going to throw this in now that I mentioned radio waves...please put down your cups and get the kiddies out of the room...thanks!

Maybe electricity hurts, but RF hertz.



[This message has been edited by Dragon (edited 06-26-1999).]

[drstawl]

OUCH!

[Dragon]

I knew you would appreciate that one, drstawl!

[jethani]

You flatter me by calling what I wrote a joke! I don't think I want to explore Faraday cages, but I'll take a guess and say that they are for blocking out unwanted RFs?

[Dragon]

Got it first time, I'm impressed!