Resources: PA Gear: Cables & Cords
Cables and cords are specialized, insulated wires that connect instruments, microphones, mixing boards, amplifiers, equilizers, effects devices, speakers and other sound reinforcement gear. The type of cable or cord depends on the kind of things that the cable or cord connects and the amount of power that the cable or cord carries. While many more types of cable, plugs and devices exist, the text below describes the most common types of cables and cords and their uses.
Instrument cables usually have quarter-inch-diameter male plugs on each end, designed to plug into one female quarter-inch output jack on the instrument and a quarter-inch input jack on an amplifier, mixing board, direct box or snake (see snake below). The signal from the instrument is VERY small- so small that electromagnetic fields (EMF) created by electric motors, flourescent light ballasts and other electrical devices are large in comparison. As a result, EMF from these common devices would distort the tiny instrument signal travelling in a cable if that cable did not protect, or shield, it from the distortion. Therefore, in addition to insulation, instrument cables also have shielding. For reasons detailed below, while instrument cables and speaker cables look very much alike, instrument cables are not interchangable with cables for unpowered speakers.
Speaker cables for unpowered speakers also usually have quarter-inch-diameter male plugs on each end, designed to plug into one female quarter-inch output jack on an amplifier, mixing board, direct box or snake (see snake below) and a quarter-inch input jack on a speaker. For speakers that do not have their own power supply, and depend on another device to amplify the signal, the signal that the speaker receives is much larger than the signal that an instrument produces. The signal is large enought that electromagnetic fields (EMF) created by electric motors, flourescent light ballasts and other electrical devices are relatively small and less likely to distort the signal travelling in the cable. Therefore, while speaker cables have jacks and insulation that make them look like instrument cables, they generally have larger gauge conductor inside of the insulation, but do not include shielding. For these reasons, cables for unpowered speakers are not interchangable with instrument cables.
Speaker cables for powered speakers also usually have quarter-inch-diameter male plugs on each end, designed to plug into one female quarter-inch output jack on a mixing board, direct box, snake (see snake below) or another speaker and a quarter-inch input jack on a speaker. For speakers that have their own power supply, the signal that the speaker receives is small like the one that instrument produces. The signal is so small that electromagnetic fields (EMF) created by electric motors, flourescent light ballasts and other electrical devices are large in comparison. As a result, EMF from these common devices would distort the tiny signal travelling in a cable if that cable did not protect, or shield, it from the distortion. Therefore, in addition to insulation, cables used for powered speakers have shielding. For reasons detailed above, while instrument cables and cables for powered and unpowered speakers look very much alike, instrument cables and cables for powered speakers are not interchangable with cables for unpowered speakers.
Patch cables often (not always) have quarter-inch-diameter male plugs on each end, designed to plug into one female quarter-inch output jack on one device and a quarter-inch input jack on another device. Commonly (not always), the connection carries a small signal like an instrument signal. Therefore, the most common patch cables are simply very short instrument cables.
Microphone cables connect a microphone to a mixing board, amplifier or snake (see snake below). Microphones have a variety of designs; the impedance (or the resistance to the flow of electricity) of the microphone is the facet that is important to the kind of cable that is appropriate. Microphones fall into two general categories of impedance: high impedance and low impedance (hi-Z and low-Z). In general, hi-Z microphones have cables with a male three-pin plug (called an XLR plug) on the end that connects with the microphone output and a quarter-inch-diameter male plug on the end that connects to the mixing board, amplifier or snake. Low-Z microphones generally have cables with a male three-pin (XLR) plug on the end that connects with the microphone output and a female XLR plug on the end that connects with the mixing board, amplifier or snake. Devices that connect in-line with the cable, and modify the impedance of the signal, are available for someone who needs to plug a hi-Z mic in a low-Z input or vis versa. Low-Z mics that connect with cables with two XLR connections send larger signals than hi-Z mics with an XLR and quarter-inch connector at each end. Therefore, low-Z mics and XLR/XLR cables are prefereable in applications in which the microphone is a significant distance from an amplifier (see snake below).
Snakes are cable systems that carry signals longer distances with less distortion than individual cables between individual components. Snakes also allow cable connections between all components in a system without the mess of individual cables between individual components. At one end, a snake has box that contains a group of numbered XLR and quarter-inch input jacks that connect to high-quality cables that leave the connection box in an insulating wrap that binds all of the cables into one very thick cable that is often more than 100 feet long. At the other end of the snake, the individual cables protrude from the overwrapping. XLR and quarter-inch plugs on the ends of the cables; numbers on the cable ends correspond with the numbers on the connection box. Performers' instruments and microphones plug into the snake's box, the high-quality cable that runs from the box carries the signal to a mixing board some distance from the stage. The numbering of the cables and the placement of the mixing board in the area where audience sits allows the person operating the board to mix all of the signals in a way that optimizes the sound that comes out of the speakers. This arrangement allows a clean stage presentation, good signal to the board and good mixing.
A note about cable quality: A wonderful amplified guitar, a premium microphone, an audiophile-quality amplifier or speaker...any/all of these things depend on the quality of the cable through which their electrical signals flow. Get the best cable you can afford. Make sure that the conductor is thick enough, that shielding is adequate, that conncetors are high quality. Your sound depends on it.