Line level - Definition and Overview

Line level is the strength of an audio signal used to transmit analog sound information between audio components such as CD and DVD players, TVs, amplifiers, and mixing consoles. Specifically, it is a signal of about 310 millivolts, although it can vary from 100 millivolts to as much as 5 volts, depending on the equipment used.

When amplifying an acoustic sound (such as voice or a musical instrument) with a pickup or microphone, a pre amplifier is used to bring the signal up to line level. The preamp can output to a mixer, or directly to a power amplifier which can drive speakers. Most phonographs also have a low output level and require a preamp; typically, a home stereo amplifier will have a special phonograph input with a built-in preamp.