Editing Line level (section)

== Line out ==
[[File:Line out symbol.svg|28px]] &nbsp;&nbsp; [[File:Line waves03-0-out.png|42px]] &nbsp;&nbsp; [[File:Line waves03-1-out.png|32px]] &nbsp;&nbsp; [[File:Line circle out.png|35px]] &nbsp;&nbsp; Line-out symbol. [[PC System Design Guide#Color-coding scheme for connectors and ports|PC Guide color]] {{color box|palegreen}} lime green.

Line outputs usually present a source impedance of from 100 to 600 [[ohm]]s. The voltage can reach 2 volts [[Amplitude#Peak-to-peak amplitude|peak-to-peak]] with levels referenced to −10 [[Decibel#Voltage|dBV]] (300 mV) at {{nowrap|10 kΩ}}. The [[frequency response]] of most modern equipment is advertised as at least 20&nbsp;Hz to 20&nbsp;kHz, which corresponds to the [[Hearing range|range of human hearing]]. Line outputs are intended to drive a load impedance of 
10,000 ohms; with only a few volts, this requires only minimal current.

=== Connecting other devices ===

Connecting a low-impedance load such as a loudspeaker (usually {{nowrap|4 to 8 Ω}}) to a line out will essentially  [[short circuit]] the output circuit. Such loads are around 1/1000 the impedance a line out is designed to drive, so the line out is usually not designed to source the current that would be drawn by a 4 to 8 ohm load at normal line out signal voltages. The result will be very weak sound from the speaker and possibly a damaged line out circuit.

Headphone outputs and line outputs are sometimes confused. 
Different make and model headphones have widely varying impedances, from as little as {{nowrap|20 Ω}} to a few hundred ohms; the lowest of these will have results similar to a speaker, while the highest may work acceptably if the line out impedance is low enough and the headphones are sensitive enough.

Conversely, a headphone output generally has a source impedance of only a few ohms (to provide a bridging connection with 32 ohm headphones) and will easily drive a line input.

For similar reasons, "wye"-cables (or "Y-splitters") should not be used to combine two line out signals into a single line in. 
Each line output would be driving the other line output as well as the intended input, 
again resulting in a much heavier load than designed for. This will result in signal loss and possibly even damage.
An active mixer, using for example [[Operational amplifier applications#Summing amplifier|op-amps]], 
should be used instead.<ref>{{cite web
 | url    = http://www.rane.com/note109.html
 | title  = Why Not Wye?
 | author = Dennis Bohn
 | date   = April 2004
 | work   = RaneNotes
 | publisher  = Rane Corporation
 | accessdate = 2012-07-15
 | quote = Outputs are low impedance and must only be connected to high impedance inputs -- never, never tie two outputs directly together -- never. If you do, then each output tries to drive the very low impedance of the other, forcing both outputs into current-limit and possible damage. As a minimum, severe signal loss results.
}}</ref>  A large resistor in series with each output can be used to safely mix them together, but must be appropriately designed for the load impedance and cable length.