Quick answer: An XLR output on a mixer, interface or preamp sends line level, typically around 1.2 volts nominal, at a low balanced output impedance. Connect it to an XLR or TRS line input, not to a microphone input. When the destination is consumer gear, attenuate or use a balanced to unbalanced cable rather than turning the output down to nothing.
XLR Output: Line Level, Impedance and What to Connect
An XLR output is the far end of a signal chain, and most problems blamed on the cable start at that end. The output decides the level, the impedance and whether the signal arrives balanced at the next device. Reading the output correctly, then matching it to the input, removes hum and gain problems before any cable is swapped. This guide covers what an output sends, how to identify it on the chassis, and how to connect it to inputs that were not designed for it.
What an XLR Output Actually Sends
An output is a driver, not a passive contact. Inside the device an amplifier stage sets the level and an impedance balances the two signal legs against the shield. That is why an output can drive a long cable while a microphone cannot: the microphone generates a tiny voltage from a high impedance source, and the output delivers a larger voltage from a low impedance source. Confusing the two is the root of most level and noise complaints.
Mic Level, Line Level and Instrument Level
Mic level sits around one to ten millivolts, line level around 1.2 volts, and instrument level in between at high impedance. Feeding a line output into a mic input overloads the preamp before the gain control has any useful range. Feeding a mic into a line input gives a signal too quiet to use. The connector looks identical in both cases, so the label and the device type are the only guide.
Balanced Output Impedance
A balanced output drives two legs and the receiving input subtracts them, which cancels interference picked up along the cable. Output impedance is typically in the low hundreds of ohms, low enough that cable capacitance over tens of metres has almost no effect on the top end. This is the property that makes long XLR runs practical.
Reading the Connector on the Gear
Outputs on professional gear are usually male XLR connectors, because the male shell protects the pins and the convention grew from the microphone side. Inputs are usually female. That convention is strong but not universal, so check the label before trusting the shell. Devices also mix XLR, TRS and RCA outputs on the same panel, and the label beside each one is the only reliable indicator of what it carries.
Male Outputs and Female Outputs
A male XLR output presents three pins inside a metal barrel, and the mating cable needs a female connector. Some interfaces use female outputs to save panel space or to allow a male to male cable, which breaks the convention and causes confusion in a rack. Mark such exceptions on the rack once and the problem disappears.
Labels, Icons and Confusing Ports
Manufacturers label outputs as OUT, MAIN OUT, SEND, or with an arrow pointing away from the unit. Combination jacks accept both XLR and TRS, and those are almost always inputs. When a panel is ambiguous, trace the signal: an output feeds a speaker or the next device, and an input receives from a source.
Matching Output to Input
Impedance bridging is the rule: the input impedance should be at least ten times the output impedance, which modern gear satisfies by a wide margin. Level is the practical issue. A line output into a line input needs no attenuation, while a line output into a mic input needs a pad of roughly 20 to 30 decibels. Many interfaces include a switchable pad for exactly this case.
Level Matching in Practice
Set the output at nominal, not at maximum, then adjust the input gain so peaks sit around minus 12 decibels. If the input gain has to sit at minimum with the output near zero, the signal is too hot and a pad is required. If the input needs full gain, the source is probably mic level and should go to a preamp.
When the Input Is Consumer Grade
A consumer input expects around 0.3 volts unbalanced and often has no pad. Feed it from a balanced output through a cable that ties the cold leg to ground at the destination end, and keep the output level low. A transformer isolator solves both the level and any ground loop in one part.
Cable Choice for an Output Run
An output cable carries two signal conductors and a shield. The shield connects to pin 1 at both ends in most installations, which is correct for interference rejection but can create a loop when two earthed devices are joined. For long runs near lighting dimmers, a star quad cable improves rejection. For short patch runs, standard two conductor shielded cable is entirely adequate. Match the cable to the run before spending more on connectors.
Two Conductors Plus Shield
Pin 1 is the shield, pin 2 the hot leg and pin 3 the cold leg. A cable built with only one conductor and the shield as return is unbalanced and will lose the rejection that the output was designed to provide. Check that both signal conductors are present before blaming the equipment for hum.
Length, Hum and Ground Lift
Balanced outputs tolerate long runs, but hum usually comes from a ground loop rather than cable length. If hum appears only when a device is connected, lift the shield at one end of that cable, or insert an isolator. Never lift the mains earth, which is a safety function rather than a signal reference.
Output Types and Their Destinations
| Output type | Nominal level | Output impedance | Cable | Typical destination |
|---|---|---|---|---|
| Mic level XLR | 1 to 10 mV | 150 to 600 ohm | Balanced shielded | Preamp or mixer mic input |
| Line level XLR | 1.2 V | 50 to 200 ohm | Balanced shielded | Line input or active speaker |
| Line level TRS | 1.2 V | 100 to 600 ohm | Balanced or unbalanced | Line input, patchbay |
| Consumer RCA | 0.3 V | 1k to 10k ohm | Unbalanced coaxial | Hi-fi input, DJ mixer |
| Instrument level | 10 to 100 mV | 10k ohm and up | Unbalanced shielded | DI box or instrument input |
| Digital AES3 | 1 to 5 V | 110 ohm | 110 ohm twisted pair | Digital input, converter |
Real-World Application Scenarios
A studio monitor run from a mixer main output uses a male XLR output into a female XLR input on the speaker, with the output set at nominal and the speaker trim at zero. A live console feeding a consumer recorder needs a pad or an isolator, because the recorder input cannot accept 1.2 volts without clipping. A church with a long run to a lobby amplifier benefits from a balanced output and a star quad cable past the lighting dimmers. A DJ booth feed to a powered monitor is a short balanced run where the output level, not the cable, sets the result.
Related Guides on This Site
Connector anatomy is covered in xlr connector and the cable build in xlr cable. For the balanced versus unbalanced distinction, see balanced xlr cable, and for the socket on the device see xlr jack.
Frequently Asked Questions (FAQ)
Q: What level does an XLR output send?
A: Professional XLR outputs send line level, nominally around 1.2 volts, from a low impedance source. Microphones send mic level, which is a thousand times smaller, so the two cannot be interchanged without a pad or a preamp.
Q: Why is an XLR output male?
A: The convention follows the microphone, where the cable carries a female connector so the pins are protected. Most professional outputs are male, but some devices break the rule, so check the panel label rather than the shell.
Q: Can I plug an XLR output into a microphone input?
A: Only with a pad of roughly 20 to 30 decibels. Without it the preamp clips before the gain control is useful. Use a line input where one is available, and engage the pad when it is not.
Q: How long can an XLR output cable be?
A: Balanced line level runs of 50 metres and more are routine, because the low output impedance makes cable capacitance irrelevant. Practical limits come from ground loops and interference rather than from the cable itself.
Q: Why does my XLR output hum only with one device?
A: That pattern indicates a ground loop between two earthed devices, not a cable fault. Lift the shield at one end of that specific cable or insert an isolator, and never disconnect the mains earth.