Hangtime's Tutorials

at a glance.... | GarageBand FAQ: your questions answered |
bsqg Backstage Quickies
|
aag All about
Audio Units
| All about
SoundFonts
| All about
Panning
|
rcg We are the Roadcrew...
|





to The DoorPost
The DoorPost - GarageBand tips newsletter is sent to you every three months and is full of extra tips on how to get the most out of GarageBand. It takes a more in-depth look at some important aspects of digital audio and home recording with GarageBand. Also: Links to free loops, effects and software instruments.
Your e-mail privacy matters; we will never pass your details on to other parties |
scales

All about......
Balanced Systems



What the heck is the difference between balanced and unbalanced?

That's easy, I'm balanced and you're not.

Seriously.

Arty, I'm not sure your brain can handle this.

I promise I'll just sit quietly and listen.

If you insist.

I insist.

Right, let's have a go then...

First a short bit of background information. An antenna is nothing more than a "tuned" length of wire. To be most efficient the length of wire matches the wavelength of the signal its supposed to send or receive (i.e. tuned to that frequency), but even if it's not tuned properly a length of wire can receive radio waves, or any electromagnetic waves of various frequencies.

So now that we know what an antenna is, a length of wire, you should be able to see that looking at it the other way around, a length of wire can be an antenna. When we're working in our recording studio, be it professional, semi-pro, or your bedroom, we have all kinds of cables (wires), mic cables, mixing console cables, and so on, so we have lots of potential "Antennas" too.

Microphone cables in particular are susceptible to noise (acting like an antenna and receiving electromagnetic signals) due in part because they often use long cables (lots of chances to pick up interference), but also because the signal level from a mic is so low to begin with, even little bits of noise can become very problematic.

The solution was Balanced Systems.

There's lots of technical detail we could cover, however in this article we're just going to cover the big reason that you can't simply plug a balanced system into an unbalanced system.

They would fall over? Hush!

The real beauty of a balanced system is the elegant way that noise is reduced. While a stereo cable and a balanced cable both have two "hot" runs of wire, along with a "ground" wire, in a balanced system both Hot wires carry the same signal, with one being 180° out of phase with the other.

I'm not scared of technical terms, I'm not scared of technical terms

You're repeating yourself again

I'm scared of technical terms

I didwarn you

Yes, I know. I'm sorry, please continue.

We can probably simplify this "Phase" bit with a couple of images of a sine wave.

This is a very simple sine wave
Balanced

The red line is the "Zero Line" and it marks 0 amplitude. The further away from the zero line the "louder" a sound is. In this example the amplitude is 3 because the highest and lowest peeks are 3 away from the zero line. We refer to the part above the zero line as positive and the part below the zero line as negative.

Something somewhat interesting happens if you were to add two identical, and in phase, sine waves together. Just like you learned in math class, adding makes things bigger, and adding two identical things together makes them twice as large
Balanced 1

In this case our amplitude becomes 6 (remember 3 + 3 = 6 and -3 + -3 = -6, each is 6 away from the zero line). But something even MORE interesting happens if we add the two together with one of the sine waves out of phase with the other (For a more in-depth article on "Phase" scroll down about halfway through this wikipedia page [Warning: Lots of math and technical info there, but there are a couple of pictures that may explain things well])

http://en.wikipedia.org/wiki/Phase (waves)

Here are our 2 signals 180° out of phase with each other, for clarity the second one is shaded purple, there's no significance to that other than being able to see it better.
Balanced 2

Notice that the highest peaks of signal 1 correspond to the lowest peaks of signal 2 and vice versa. And if we were to add them together it would look like
Balanced 3

Doing the math again we add 3 + -3 = 0 and -3 + 3 = 0. So the signal that we create looks like this
Balanced 4


A Straight line, IOW, silence. The waveforms completely cancel each other out.

So what good is that? I don't want the sounds I'm trying to record to be silent!!

Patience, grasshopper. Balanced system's kung fu is strong...

Hopefully you've grasped the concept enough to understand the basics. Two identical and in phase signals when added together get louder. Two identical, but 180° out of phase signals cancel each other out and leave silence. This simple bit of knowledge gives us a powerful weapon against electromagnetic interference, or what usually shows up in our recordings as hum or static.

In a balanced cable, remember, the identical signal is sent through two wires, but out of phase with each other. Now imagine a noise enters our cable, maybe the air conditioning system turned on and created some interference. THAT noise entered both wires at the same time so IT is IN phase

I think I see where you're going!

I'll bet you do! At the other end of the system the phase of the second wire is reversed 180°, putting the noise 180° OUT of phase with itself so...

So the noise cancels itself out!! Yay for canceling!

What about balanced systems

YAY for balanced systems!!

And me?

No.

Why not?

I would have figured it out myself

Yeah. Right.

Oh okay, YAY for you!

Better.

{Raises Hand}

Yes

Um, how do you tell them apart? I mean the cables.

For the most part it's obvious. XLR style connectors that look like this...
XLR
...are balanced. To the best of my knowledge, always, I've never seen an unbalanced system that uses XLR jacks or plugs (IOW they may exist, but I've never run into them.

1/4" TRS (Tip/Ring/Sleeve) is less obvious. Remember the cable doesn't make the system balanced, the system does. TRS cabling is identical whether it's used for stereo or balanced mono. The TRS plug, which I'm sure you're familiar with looks like this:
Balanced 5

If you can't see a difference it's because there is none. The difference is that the jack will likely be labeled "Balanced", or at least the documentation that came with the device will tell you that it is. More often than not if you see a TRS jack, it is unbalanced and is stereo.

So what about THIS one:
Balanced 6

Ummmm

This would be a good example of a TRS plug for use in a balanced system (notice how the 1/4" plug looks pretty much like any other TRS 1/4" plug, butsince the other end is an XLR style connector you can tell it's for use in a balanced System). If you WERE to plug one end into a Mic, and the other end into a stereo TRS jack, what you'd end up getting is the Left channel and Right channel both with the same signal, but 180° out of phase ... not something you generally want)

And I think that wraps everything up.

Yay for wrapping!

Indeed.



To the Top