Mic Level vs Line Level
Definition
Mic level, instrument level and line level are the nominal signal levels found in audio equipment. A microphone typically delivers between about −60 and −40 dBu, so microphone preamplifiers commonly offer 60 to 80 dB of gain. Professional line level is +4 dBu nominal (about 1.228 V) and consumer line level is −10 dBV nominal (about 0.316 V). Instrument level, from guitar and bass pickups, lies between mic and line level and comes from a high-impedance source. A line-level signal sent into a mic input without an attenuator (pad) overloads the preamplifier, while a mic-level signal sent into a line input is far too weak to be usable.
In the field
A DI box converts a high-impedance, unbalanced instrument or line signal into a low-impedance, balanced signal at mic level, so that the source can travel over a long stage cable into a mic input. It is standard equipment on stage for keyboards, basses and playback computers.
Related lessons
Sources
- Line level (Wikipedia) : +4 dBu ≈ 1,228 V, −10 dBV ≈ 0,316 V ; niveaux micro et instrument · en.wikipedia.org
- Shure, « Microphone Volume - High and Low Impedance » : niveaux de sortie micro faibles et impédance · service.shure.com
- Radial Engineering, DI Questions, rôle de la DI : haute impédance asymétrique vers basse impédance symétrique · radialeng.com
- Ballou, Handbook for Sound Engineers : dBu référencé à 0,775 V, dBV à 1 V