Microphone Lines (cables)
There are two ways to connect a microphone to equipment. The equipment will require either an unbalanced or balanced line.
Unbalanced Line
An unbalanced cable or line has one conductor and a shield. The shield is also the ground. These cables use a two-conductor plug like a 3.5 mini plug or ¼" plug. The audio signal travels on the center conductor of the cable, and the shield has no signal. The cable is therefore said to be “unbalanced”.
Balanced Line
A balanced line has two conductors and a shield. The shield is also the ground. These cables use a 3 conductor plug, normally an XLR connector. The audio signal travels on both conductors side by side, and the shield has no signal. Since these two conductors have the same signal, they are said to be “balanced”. A balanced line has an advantage in that it will carry the signal great distances with very little loss. A balanced line may be run up to 2,000 feet or more.
Microphone Level and Line Level
Whenever we want to connect microphones and equipment together, we must be sure the inputs and outputs have a matching voltage level. There are two very important voltage levels to remember when connecting audio equipment together, microphone level and line level.
Microphone Level
This is the voltage of microphones. It is a very small voltage of one milivolt (.001 volt).
Line Level
This is the interconnecting voltage level of devices such as CD players, tape decks, audio mixers and most all other non-microphone audio equipment. This voltage is one volt (1volt).
A line level output must be routed to a line level input. A microphone level output must be routed to a microphone level input. Line level input and output are also called auxiliary input and output. Any product that is not a microphone uses a line level connection.