Hello everyone! Today we’re going to discuss cables used in professional audio and electric instruments, like guitar and keyboard. The terminology can be confusing sometimes, so we’re hoping to clear that up and give everyone a basic understanding of what audio cables to use for what application. The audio cable is the basic building block of a sound system and there are three primary types used in any sound system, guitar setup, or stage.
The line level (or instrument) cable is probably the most common. This is the cable used to plug a guitar or bass into an amplifier or a keyboard into a sound system. An instrument cable is made up of a single copper conductor at its core that is insulated and then wrapped with a copper shield wire. The shield can be wound around the center conductor or braided; both are very common. The center conductor carries the audio signal from one place to another and the shield is there to keep noise out of the signal. Instrument cables are susceptible to signal degradation when using cables over 20 feet long.
Microphone or balanced line cables are a better solution to noise cancellation than a standard line cable. A microphone cable has two internal conductors (+ and -) with a shield around both. This was designed for a “balanced” signal to reduce noise. The signal is split into two equal but out of phase parts (the – part is “flipped” over) and sent down each conductor. As the signals travel down the cable they pick up the same amount of noise. Once the signal reaches its destination, the balanced input of the mixer or whatever is receiving the signal, “flips” the – signal back in phase with the + signal and recombines them. This puts any noise picked up along the – conductor out of phase with noise picked up on the + conductor, cancelling it out. An important thing to remember about balanced cable is that if the equipment on either end of the cable does not have balanced ins and outs, the cable makes no difference at all, as the signal splitting and phase shifting is not done by the cable itself.
Speaker cables are perhaps the most misused cable in the audio industry. Unlike an instrument or microphone cable, a speaker cable does not have a shield that wraps the internal conductors. Speaker cables are designed to carry higher current signal than audio cables and as such are usually larger in diameter. A speaker cable is only designed to carry a “powered” signal such as between an amplifier and a speaker (thus the name). While they can be used as an instrument cable in a pinch, it has no noise cancellation properties and will probably pick up any interference that may be around.
While there are many other types of cables used in the audio industry, these are the basic building blocks of any sound system. Some things to remember about them:
• Guitars, basses, and keyboards use the same cables (unbalanced line) but have different level outputs. Make sure the appropriate amplifier is used.
• Balanced line level is used for many applications, not just microphones. Microphones have a lower output level than balanced line and so need a mic preamp to plug into (these are built into any mixer out there).
• NEVER use an instrument or line level cable to connect a speaker to a power amp. ONLY powered speakers use line or balanced line inputs. Also, avoid using speaker cables on powered speakers, this will just induce noise.
• Just because a unit has an input or output that looks like a microphone cable (three prong or XLR), doesn’t mean it has to be a microphone plugged into it. It does however usually mean that input or output is balanced.
So there’s a little background into common cables and their uses. If you find yourself wondering about what cable to use or how an output or input works on a piece of gear, check the manual they will usually tell you what level input or output the gear needs to operate correctly. There is also a wealth of information online about balanced vs. unbalanced and different types of cables if you feel like researching this further. Thanks for reading!