There are 3 types of cables we are going to talk about, and when to use them. Unfortunately, you can’t always tell what type of cable you have just by the connector on the end (XLR, 1/4 inch, etc.), but most connectors have a sleeve that unscrews quickly giving you access to see how the wires are connected to the end so you can figure it out. We will cover 3 generic types of cables: microphone, instrument, and speaker cables. Using the correct cable for appropriate applications will help eliminate 99% of possible buzz and hum, and in some cases make the system safer to operate.

If you’ve gone to the shack that sells radios, you may have seen “stereo” and “mono” connectors. We are going to use big-boy words, and call these balanced and unbalanced respectively. Before we talk about connectors though, let’s look at the cables. Audio cables are made up of either 2 or 3 wires typically. Balanced cables have 3 wires: a positive, negative, and a ground. Unbalanced have 2 wires: a positive and a ground. If you can count to 3, you can easily see the difference between the 2.

This is an unbalanced cable with a 1/4 inch connector. The positive wire is surrounded by the clear insulation and is solded to the short metal part connected to the tip of the connector. The ground wire is soldered to the longer metal part which is connected to the sleeve of the connector. To help avoid this cable from shorting out, it’s best to not leave any extra of the wire exposed, which is why it may be a little difficult to see the ground wire coming out of the cable. Another note about this unbalanced cable, is that positive wire is surrounded, or shielded, by the ground wire(s) which can be wrapped or braided around the positive wire. The only way for this cable to reject any interference it encounters is to capture the noise (from lights, power cords, radio transmissions, etc.) and ground it. If that noise gets into your positive wire, you’re stuck. To solder the ground wire to the connector, all the strands of copper making up the wire are gathered to 1 side, twisted together, and attached. These cables are used to connect guitars, keyboards, etc., and we’ll get into more specific applications shortly.

These are both balanced. On the left is an XLR, and on the right is a 1/4 inch, with tip, ring, sleeve. You can see the 3 distinct wires, which are the positive, negative and ground. These cables also have a shield as the 1st cable, but it is not visible in these photos. The shield that rejects unwanted noise is a piece of foil wrapping the 3 wires the entire length of the cable. Balanced cables though, also have another trick when it comes to rejecting interference.

It’s my goal to not get into heavy technical issues on this blog (or in my training seminar), but this is easy to understand and is way too cool! Forgive the short physics lesson here. A microphone turns sound into an electrical current. It then sends that current down the positive and negative wires. Before it goes down the negative wire though, the audio signal is flipped ‘out of phase’, meaning it is the exact opposite of the signal on the positive wire. Should the cable pick up interference on the way to the console, that interference will look exactly the same on both the positive and negative wires. When you connect the cable to your mixing console, it will flip the signal on the negative wire back into phase, meaning now the interference is canceled out and equals zero (so you can’t hear it), while the audio from the microphone is now the only thing you hear!

This last cable we are going to cover is a speaker cable. Of course it also has a 1/4 inch connector, which makes it difficult to distinguish from an ‘instrument’ cable, and thus why I’m writing this… Remember how the unbalanced cable had a positive wire insulated then wrapped up by the ground wire? A speaker cable will also have 2 wires, but they will run through the cable side by side. This isn’t the best photo, but hopefully you can see the black and red wires in the cable are side by side. So, what happens if you use a speaker cable to plug a guitar into a guitar amp or a keyboard into a direct box? It may still work, but it also may pick up interference since it’s not shielded. It’s a lot more serious if you use an unbalanced instrument cable to connect your monitors or speakers to an amp. You can google the physics and technical side of this if you like, but the simple answer is that those cables are designed to carry unpowered signals, and thus it is not a good idea to send 800 watts of power through them.

Most of your audio gear (not talking about instruments) that have 1/4 inch connectors will accept balanced or unbalanced cables, unless you have vintage gear that probably should be in a recording studio anyway, and the gear will work fine with either. My recommendation is to use TRS (tip, ring, sleeve) / balanced cables whenever you can! Guitars, keyboards, and other instruments will use an unbalanced output, that if connecting directly to your audio system (and not a guitar amp or instance) should be interfaced with a direct box. Part of the job of a direct box is to turn that signal into a balanced one. Why don’t instruments just have balanced outputs you ask? I wish I knew!!! Seems like a good idea to me.

EXTRA CREDIT

If you’re still with me here- congrats and thanks. Your A/V equipment probably has all RCA connectors, which should now be identifiable to you as unbalanced. For short cable runs of 10 feet or so, it’s ok to just plug those directly into your mixing console, otherwise, use a direct box for them as well. Here’s the pop quiz to earn your extra credit though: what about headphone connectors, like shown on the right here? Are headphone cords balanced or unbalanced?

Try to figure it out before reading the answer.

No, seriously, it’s a tricky question. Think about it.

It’s not a trick question, but here’s the answer…

Headphones use a TRS connector, which appears to be balanced. The answer though, is that headphone cords are actually carrying TWO unbalanced signals. The headphones have 2 outputs- the left ear and the right. Both of these share the ground connector, but the tip feeds the left ear, and the ring feeds the right. This is why you sometimes see home stereo equipment dealers talking about mono plugs (like RCA connectors) and stereo plugs (like 1/4″ or 1/8″ connectors).