Line level

Line akin is a appellation acclimated to denote the backbone of an audio arresting acclimated to address analog complete amid audio apparatus such as CD and DVD players, TVs, audio amplifiers, and bond consoles, and sometimes MP3 players.

In adverse to band level, there are weaker audio signals, such as those from microphones and apparatus pickups, and stronger signals, such as those acclimated to drive headphones and loudspeakers. The backbone of the assorted signals does not necessarily associate with the achievement voltage of a device; it additionally depends on the source's achievement impedance, or the bulk of accepted accessible to drive altered loads.

Nominal levels

A band akin describes a line's nominal arresting akin as a ratio, bidding in decibels, adjoin a accepted advertence voltage. The nominal akin and the advertence voltage adjoin which it is bidding depend on the band akin actuality used. While the nominal levels themselves vary, alone two advertence voltages are common: decibel volts dBV for customer applications, and decibels unloaded dBu for able applications.

The advertence voltage for the decibel volt (0 dBV) is 1 VRMS, which is the voltage appropriate to aftermath 1 milliwatt mW of ability beyond a 1 kiloohm kΩ load.1 The advertence voltage for the decibel unloaded (0 dBu) is the voltage appropriate to aftermath 1 mW of ability beyond a 600 Ω amount (approximately 0.7746 VRMS)

Impedances

Impedance bridging is active to ensure that actual little ability is transferred and the band in ambit does not amount bottomward the achievement of the antecedent device. When a band out signal, with its achievement impedance of about 100 Ω, is affiliated to a band in with an ascribe impedance of 10 kΩ, best of the voltage appears beyond the ascribe attrition and about none of the voltage is alone beyond the output. In effect, the achievement impedance of the source, and the ascribe impedance of the band in anatomy a voltage affiliate with a blow aspect that is ample about to the admeasurement of the alternation element, which ensures that little of the arresting is shunted to arena and that accepted requirements are minimized.