Audio cables can be a very deep subject, but for the live sound technician, it doesn’t have to be. In this article, I’ll cover the basics of audio cables, the different types of cables, connector types, and when and where to use a certain cable type. I’ll also mention a few no-no’s when it comes to using audio cables. I generally won’t be referring to other types of cables in this article, such as power cables or digital cables, but some of the information here would apply to those cables, too. I may discuss those cables in a future article.
I’m sure you’ve seen all types of audio cables, from microphone cables, to patch cables interconnecting outboard equipment, to speaker cables. While the popularity of wireless microphones and other wireless devices has reduced the number of cables typically needed on the typical stage, cables are still a necessity for most systems and knowing their makeup and proper use is essential. I’ll forewarn you: This article is quite lengthy, but a treasure trove of good information. So, let’s get right to it!
Unbalanced and Balanced Cables Explained
Audio cables can be broadly categorized into two major types based on the signals that they carry: unbalanced or balanced. These two types of audio signals and cables are very different from each other. Unbalanced audio cables carry unbalanced audio signals. They are unbalanced signals because one of the conductors is carrying the signal voltage and the other conductor is grounded, or carrying no signal voltage. So, both conductors have different voltages on them, and, therefore, they are unbalanced. Unbalanced audio cables usually have two conductors, or wires, within the cable, and also on each connector. One of those wires is usually a grounded, shielded conductor in cables carrying low-level audio signals, such as patch cables. A 1/4″ TS, or tip-sleeve, phone plug is a good example of a connector usually used on unbalanced cables. Another common unbalanced connector is the Phono connector, or the RCA connector.
Balanced audio cables carry balanced audio signals. A balanced audio signal is made up of two signal paths, or, again, two wires, but usually a third conductor, which is a ground connection, is also present. The two signal-carrying conductors are normally referred to as hot and cold, or positive (+) and negative (-). But, be careful with these designators. The cold or negative connotation is not the same meaning as ground. Ground is an additional, third conductor. So, the three conductors of a typical balanced audio cable would be hot, cold, and ground.
The two signal-carrying conductors of a balanced audio cable have equal amounts of the same audio signal, or voltage, on them at all times. But, the signal found on the cold conductor is of the opposite polarity, or the mirror image, of the signal on the hot conductor. This creates an interesting condition where, at the destination, these two signals are summed, or added algebraically, to derive the resultant audio signal. Since the resulting audio signal is really the net difference of these two balanced signals, any noise that was introduced to the conductors naturally cancels out. That is the single biggest advantage of balanced audio signals: Noise immunity. Well, not really noise immunity, but the ability to filter out any noise that invades the balanced conductors quite effectively, simply using basic math.
So, why then aren’t all cables balanced to take advantage of its inherent noise immunity? First of all, balanced cables require either special circuitry to interface with them, both in sending and receiving the balanced audio signals, or they require the use of specialized audio transformers. Both of these options typically cost extra money to the manufacturer, raising the costs of the equipment. So, for economical reasons, unbalanced signals are used on some lower priced outboard equipment. Secondly, since extra circuitry is needed for the proper handling of balanced signals, it is possible to degrade the sound quality or compromise the fidelity of the audio if care is not taken in the circuit design and component choices of the unit. In reality, economics, again, play a huge role in determining the choice of parts used by a manufacturer, especially in the equipment often found in a typical church sound system. And, finally, the advantages of balanced audio cables are most often only seen in long cable runs or very low-level audio signals. To some degree, there are no real advantages to using balanced cables for very short runs versus high quality unbalanced cables. But, it really all depends on the equipment, its design, the choice of cables, and the environment surrounding the cables and the sound system, specifically in regards to electrical interference and noise.
Application TIP: For short cables that are only a few feet, unbalanced connections are usually very adequate, assuming the cable is of high quality. For equipment that gives you the choice of either, such as the output from wireless microphone receivers, go balanced for cables longer than 9′, and whichever is more convenient for the shorter runs.
Now that you know the difference between balanced and unbalanced cables and connections, it is important to understand that they are technically not directly interchangeable. Anytime you go from balanced to unbalanced, or from unbalanced to balanced, you must use a matching transformer. These can simply be direct boxes (DI’s) or inline adapters or transformers. But, take notice. Most adapters are not matching transformers. If they are, it will usually be labeled on the adapter. If you are simply using an adapter without any type of impedance matching, you are asking for trouble. Also, poor quality matching transformers can, and will, ruin your audio quality. A perfect example are the adapters once sold by Radio Shack (see photo) that I see from time to time. Stay way from them. On the other hand, the ones made by Switchcraft and other brands, that look very similar, are much better. They are also a bit more expensive.
No-No’s: Stay away from poor quality cables…Period. To some degree, you get what you pay for. If you purchased some 6′ unbalanced cables from eBay for $1 each, you are certainly asking for trouble. My advice is to save yourself, and the tech crew, the headache from hours of troubleshooting later and buy decent cables from a reputable dealer. Besides, the church is no place to skimp in preference of poor quality junk; cables included.
There are several popular connector types used in audio, and, thankfully, most all of them are standardized between all equipment manufacturers. The two most popular types found in professional audio equipment would be the XLR connector and the 1/4″ phone connector. Let’s look at these connectors, as well as a few others the live sound technician will need to know.
The XLR connector is one of the two most popular connectors in professional audio. It is primarily used in balanced audio applications, but will also be found in certain digital audio platforms. While the connector is available in several different pin numbers, or conductors, professional live sound primarily uses the 3-pin variety, simply referred to as an XLR3 connector. This connector may also be called a Cannon connector, by some, in tribute to it’s inventor and original manufacturer (which I believe still manufacturers this connector today). But, at least in the US, connectors manufactured by Neutrik and Switchcraft have been the most popular connectors found in modern audio equipment and most audio cables for the last couple of decades.
This connector will be found almost anywhere microphones are used in professional audio, from microphones, to microphone preamplifiers, to audio mixers, and much more. While it is primarily used for microphones and interfacing microphones to audio equipment, it is also found on audio equipment that uses balanced inputs or outputs, not necessarily directly related to microphones. 3-pin XLR connectors are also found on some older stage lighting equipment for use with the DMX communication standard. Look around a typical live concert venue or recording studio and you may find 4-pin, 5-pin, and other types of XLR connectors.
The 1/4″ phone connector may be used in balanced or unbalanced applications, depending on the specific connector used. It can also be referred to as a 1/4″ TRS or TS connector, depending on whether it has two or three conductors. A 2-conductor phone connector, sometimes called a TS connector, representing the physical construction of the connector, will have a tip conductor and a sleeve conductor. When used on an unbalanced cable, the tip would connect to the hot conductor, or signal wire, and the sleeve would connect to the shield/ground. Likewise, a 3-conductor phone connector is typically referred to as a TRS connector. When used on a balanced cable, the tip usually connects to the hot conductor, the ring connects to the cold conductor, and the sleeve connects to the ground conductor.
There are a couple of smaller varieties of this connector that have become popular over the last couple of decades. The 1/8″ mini phone connector, or 3.5mm connector, is found on personal audio equipment, such as headphones and earphones. The iPhone uses a 1/8″ TRRS connector, which is a 4-conductor variety. It uses this connector since both microphone and speaker audio is present, utilized by the special Apple earphones.
One other phone-type connector to mention is the sub-mini 3/32″ connector. It is even smaller than the 1/8″ connector, and is not very popular. But, in case you run across one, you’ll recognize it and know it’s not the same as a 1/8″ connector.
The phono connector, or RCA connector, is a very popular connector found on consumer audio and video equipment, such as CD and DVD players, among many other devices. It is also used as a standard connector for S/PDIF digital audio, which is found on some professional audio equipment. The connector utilizes two conductors: a center pin and an outer shield. So, this connector is used only in unbalanced applications.
Look on the back of most music keyboards and you will find this interesting connector: the 5-pin DIN. This connector is the standard connector used for the MIDI protocol, which is used to send and receive MIDI data to and from musical keyboards, synthesizers, certain audio processors, and even computers. It can even be found on certain audio mixers for automation and control of the mixer by a computer or music keyboard. One important myth to address, here: No audio appears on these connections. MIDI data is not audio, it’s data. Research MIDI if you are interested in more information about how the protocol works.
The SpeakON connector is a speaker connector developed by Neutrik. For connecting amplifiers to speakers, it is an improvement over the 1/4″ phone connector traditionally used for this task. First, the SpeakON locks securely in place without the worry of the connector being accidently pulled out, especially when used for stage monitors. Also, the connector can handle higher currents and exhibits less resistance at high power levels, something the 1/4″ connector was lacking. The SpeakON is a 4-conductor connector, and can be used to carry one or two separate speaker signals; for standard speaker setups, or for biamping configurations. It is also designed to be used specifically with cable intended for speaker applications.
A few other connectors found in pro-audio would be the Toslink optical connector for ADAT digital audio; the RJ-45 connector used in ethernet and other newer, and sometimes proprietary, networking protocols; and the BNC connector, which is found on wireless microphone receivers for antenna connections, as well as in digital clocking signals for digital audio devices. Whew! I think that about covers most of them!
Microphone cables are predominantly balanced cables, containing three conductors (two conductors plus a ground shield) terminating in XLR-type connectors on each end: a male and a female. The female connector connects to the microphone and the male connector connects to the audio mixer (or snake, wall plate, etc.). Female XLR connectors made by the most popular brands (Switchcraft, Neutrik, etc.) contain a locking mechanism that requires the push of your thumb to release before removing the connector. Likewise, when inserting the connector into your microphone, be sure the connector is properly pushed all the way in by listening for the “click”.
One of the most important considerations when purchasing microphone cables for the church is their ruggedness. So, the quality of the cable is very important. Mogami makes some of the best cables on the market, but they are quite pricey. Take care of, they can last a lifetime. I’ve also had good results with Pro Co and Rapco/Horizon, but they may require the occasional repair.
Note: Learning how to repair microphone cables and replace audio connectors is a great skill for the church sound technician to learn. It’s not extremely difficult and can certainly come in handy. There are plenty of resources online (YouTube) on how to replace XLR connectors on mic cables, so I won’t go into that, here. But, if you decide to learn, make sure you use a quality soldering iron or station (no old-fashioned soldering guns, please). Just trust me!
Patch cables refer to the interconnecting cables used to connect your CD players, computers, wireless mic receivers, and various pieces of outboard gear to the audio mixer. While some equipment may use the XLR connector like found on microphone cables, many do not. Those units that do use XLR connectors are certainly using balanced audio connections. For most equipment, though, the 1/4″ phone connector is the popular choice for patching between different types of audio equipment. Since the 1/4″ connector can be either TRS or TS, care must be taken to identify which is used on a particular piece of equipment. This determines whether the connection will be balanced or unbalanced. The rear panel of the equipment will usually be labeled, letting you know of the connection is balanced, unbalanced, or either. If not, a peek into the owner’s manual will be necessary. Above all else, be consistent in your patching. If you use balanced at one end of the cable, be sure to also use balanced at the other end. If you have to go from balanced to unbalanced, or vice-versa, then remember to use an appropriate transformer, matching adapter, or direct box.
A unique type of patch cable is the insert cable. The specially wired insert cable properly interfaces an outboard processor with 1/4″ TS connectors to the audio mixer’s insert jack. This cable has a single 1/4″ TRS phone plug on one end and two 1/4″ TS plugs on the other end. It is primarily designed for connecting an outboard audio processor (i.e. equalizer, compressor, effects unit, etc.) that has unbalanced, 1/4″ TS connectors to the 1/4″ insert jacks found on many audio mixers. Be advised! Even though an insert jack is a 3-conductor, TRS connection, it is not a balanced connection. It is comprised of an unbalanced input, an unbalanced output, and a ground.
Application TIP: Direct boxes, or DI boxes (direct interface), allow unbalanced outputs from devices such as keyboards, guitars, and almost any other device to properly interface to an XLR, balanced input. While most audio mixers usually have 1/4″ unbalanced inputs, most stages are either wired for XLR inputs only, or a snake exists where stage microphones and instruments must be utilized for routing to the audio mixer. In both cases, a direct box must be used to connect unbalanced outputs from an instrument or device into the snake or XLR connectors.
As for my recommendations on direct boxes, I personally use Radial and Whirlwind interfaces. But, Pro-Co and Behringer currently make decent DI boxes, too. The Countryman has been around for decades and is a favorite for many musicians. Again, you probably get what you pay for, here. Some DI’s are active, meaning they have internal circuitry, and so they require a 9V battery or phantom power from the audio mixer. So, if you have one of these DI’s, or plan to get one, be sure it gets the power it needs!
No-No’s: Do NOT use “homemade” cables (or cables designed for a different purpose) that connect balanced outputs to unbalanced inputs, or unbalanced outputs into balanced inputs, especially XLR microphone inputs found on an audio mixer or snake box. In an quick and necessary emergency, such connections may work, but problems, such as noise, interference, improper audio levels, and even equipment damage, could result. Connecting the unbalanced, 1/4″ output of a keyboard directly into a snake or audio mixer’s XLR connector using a homemade cable, or the wrong cable without the use of a direct box, can damage your keyboard or audio mixer IF phantom power is present. And there is a good chance phantom power is either active, or could be activated, on those inputs. You have been warned.
Speaker cables in professional audio are usually two or four conductor cables that terminate with Neutrik SpeakON connectors. Some smaller, or older, loudspeakers may use 1/4″ TS connections, but the SpeakON’s are a much better option. The cable, itself, can be cable specifically made for loudspeaker use, or a properly chosen electrical grade cable, such as SJ-type cable. For speakers wires that will be used on a portable sound system, the cable needs to be extra durable, having an adequate insulation to protect the internal conductors. This isn’t as iportant when purchasing cable to be permanently installed in walls or the stage. When selecting the size, or gauge, of the wire, it is important to consider the amplifier’s power rating, in watts, and then calculating the length of cable required. Higher power requirements and/or longer runs will need larger gauge (smaller gauge numbers) cables. When in doubt, consult a reputable dealer when purchasing speaker cables.
No-No’s: Do NOT use instrument cables as speaker cables. I see this quite often with stage monitors. Instrument cables use shielded, small gauged wire, not suitable for the power levels that stage monitors use. Also, the electrical nature of the shielded conductor can cause excessive amplifier loading, and in certain situations, could cause speaker and/or amplifier damage. While the risks are low with modern amplifiers, the risk is there. Only use instrument cables for instruments, patching, and low-level signals between equipment, never for loudspeakers. Likewise, never use speaker cables as instrument cables. They are not shielded and will not protect the audio signals from noise and interference.
There is a lot more to cables and interfacing than meets the eye. And, I could probably write a whole series of articles just on this subject, both from the technical perspective and the sound technician’s perspective. But, if you understand the basic concepts explained within this article and pay attention to your outputs and inputs, you should have the information you need to have a good sounding, properly wired system. And, as always, if you or your church needs the help of a professional concerning anything presented in these articles, you are certainly welcome to contact me.
In the next article, I will discuss proper audio levels and gain settings on your audio mixer from your input sources, such as microphones, instruments, and other devices. There seems to be quite a bit of misinformation on the internet, and held on by misinformed sound technicians, regarding proper gain setups on an audio mixer, so I’ll lay out the procedure for getting your audio levels setup properly…and done the right way.