Mixer with no audio, a dead channel or no cue: mixer diagnosis.

When a mixer stops producing sound, the instinct is to touch several controls at once. That is the mistake: the mixer is a chain, and each symptom belongs to a different link. This walkthrough covers five specific faults repeatedly reported in booths: a mixer with no audio, a dead channel, a CDJ not coming through the expected channel, headphones with no cue and no booth sound.

The logic is always the same: work from the source towards the room, checking one point at a time. If sound appears when you move a control, you have found the link; if nothing changes, the fault is downstream rather than in that control.

Mixer with no audio: start with the master

If the mixer produces no audio at all, start with the overall system. Check that the room equipment is powered on with its own volume at a reasonable position, that the master cable is in the correct connector and that the master level meter lights up when there is signal. If the meter moves but there is no sound, the fault is in the room equipment or cable; if it does not move, the fault is inside the mixer.

Then work through the controls in this order, as described in the official documentation: source selected on each channel, trim halfway, channel fader up, crossfader in an active position and master level at its working point. A fader left down from a previous session or a crossfader pointing to a silent channel is enough to leave the room silent.

If the fault occurs only with one source type, such as a connected computer, check the software output configuration: the program must send each deck to the corresponding physical output, rather than a device that no longer exists after an update. An unannounced change of audio source is one of the most common causes of a silent mixer with everything powered on.

Dead channel: follow the channel chain

A dead channel is a single channel that produces no sound while the rest of the mixer works. The quick test: connect another known source to that same channel. If it plays, the channel is healthy and the problem is in the source or its cable; if it does not, the problem is in the channel.

Within the channel, the order is: input selector in the correct position, trim adjusted, mute button disengaged, fader up and, if the channel feeds the crossfader, check the crossfader curve and position. Then inspect the connector: a poorly soldered jack or bent pin causes a channel to come and go, which can be mistaken for an electronic fault when it is actually mechanical.

If the channel works with other tracks from the same program, also check the software output assignment: each deck should come through the channel that is supposed to control it. The full architecture and names of every control are covered in Mixer anatomy: inputs, outputs and gain.

A CDJ does not come through the expected channel

A CDJ fails to appear on its expected channel and appears on another, or none at all. This is usually not a fault; it is an assignment. Professional mixers let you choose whether a channel receives the internal deck controlled by software or the physical input connected at the rear, and many models also have a line/phono switch that must match the connected equipment.

Check three things. One: the channel input selector points to the correct deck. Two: the rear switch is set to line for DJ equipment and to phono only when connecting a turntable. Three: if you use a network link, player numbering matches the channels the mixer expects; duplicate or out-of-order numbers disrupt the allocation.

The fourth point is physical: a loose RCA connector in position 2 causes sound to appear on 3 or nowhere, and this is the cheapest fault to find. Before opening any menu, move the cable and listen to whether the symptom follows it or stays on the channel.

Headphones with no cue: mix, level and assignment

Headphone monitoring has its own chain and level control. If there is no headphone sound, check in this order: the cue button for the channel you want to hear, the cue/master mix position, headphone level and finally the connector, usually quarter-inch and also accepting minijack adapters.

A common mistake is to raise the headphone level with the mix set entirely to master while the channel is cued: you hear the room, but not the track you are preparing. Another is to forget that some mixers send monitoring to two separate outputs, one for you and another for the next DJ; silence on the second does not mean a fault.

Once monitoring works, set it up for use: a comfortable level without fatigue, the mix centred for comparison and a fixed volume rule between sessions. Monitoring and the pre-listen signal are explained in Cue, PFL and monitoring.

No booth sound: the output controlling the booth

Booth is an output independent of master, with its own connector and volume control, intended to let the booth hear without depending on what the room hears. The opposite situations can therefore occur: sound in the room but not the booth, or vice versa.

Check that the booth cable reaches a powered monitor, the mixer’s booth control is not at zero and the monitor has its own volume set. If the monitor works with another source, the problem is in the mixer or cable; if it works with none, the problem is in the monitor or its power supply.

Failing to understand this separation causes the classic mistake of raising master because the booth cannot hear, when the room is already above level. Booth is adjusted separately precisely to prevent this: booth level and room level are two different decisions.

Connection mistakes mistaken for faults

Before considering repairs, rule out half the cases with a physical inspection: dirty contacts, half-inserted connectors, spare cables stored with broken conductors and adapters that do not pass the full audio signal. Contacts are cleaned and cables tested by moving them; if the symptom follows the cable, there is nothing to repair in the mixer.

The second set of misunderstandings concerns levels. A source with trim too low sounds weak and resembles a broken channel; a source with trim too high cuts out and resembles a damaged amplifier. Set each source’s level before judging the channel, and use meters as a reference rather than a target.

Next step

Once the signal comes out where it should but sounds dirty, the problem is no longer routing but levels and grounding. The next guide covers distortion, hum, ground loops, dropouts and latency.