Live Sound Troubleshooting: Solving Common Audio Problems

Live sound troubleshooting skills separate confident engineers from panicked ones. Problems occur at every show; systematic diagnosis and swift resolution keep performances on track. Understanding common problems and their solutions enables quick recovery under pressure.

Systematic Troubleshooting Approach

Follow the signal flow when diagnosing problems. Audio travels a predictable path from source to speaker. Identify where in that path the problem occurs.

Divide and conquer by testing at midpoints. If signal reaches the mixer but not the speaker, the problem is downstream from the mixer. If signal does not reach the mixer, the problem is upstream.

Substitute known-good components to isolate failures. Swapping a suspect cable for one known to work identifies whether the cable caused the problem.

Make one change at a time when troubleshooting. Multiple simultaneous changes confuse diagnosis. Change one variable, test, then proceed.

No Sound From a Channel

Check the obvious first: Is the channel unmuted? Is the fader up? Is the gain turned up?

Verify the source is producing signal. Speak into the microphone or play the instrument. Watch the channel meter for activity.

Trace the signal path. Check cable connections at source, stage box, and mixer. Replace suspect cables.

Confirm phantom power for condenser microphones. These microphones produce no signal without +48V power.

Check routing and bus assignment. The channel must route to the correct output for sound to reach speakers.

No Sound From the Entire System

Verify speakers are powered and connected to the mixer. Check power indicators on powered speakers.

Confirm the mixer main outputs are active. Check master fader position and main output meters.

Test with a known signal source. If a phone playing music through the mixer reaches speakers, the system works; the problem is upstream.

Check power amplifier status for passive systems. Amplifiers need power and proper input connections.

Hum and Buzz Problems

60 Hz hum (or 50 Hz in some countries) usually indicates ground loop issues. The problem creates a loop in the ground path causing electromagnetic interference.

Try the ground lift switch on DI boxes first. This simple fix addresses most hum from direct-input sources.

Connect all audio equipment to the same electrical circuit when possible. Different circuits have different ground references that can create loops.

Isolate the offending source by muting channels one at a time. When the hum disappears, the last-muted channel is the culprit.

Feedback Issues

Identify the source by muting channels systematically. When feedback stops, the last-muted channel is causing it.

Reduce that channel’s monitor send first. Feedback usually enters through monitors.

Reduce gain on the problem channel. Less amplification means less feedback potential.

Apply EQ cuts to problem frequencies. Use graphic EQ on monitors or parametric on channels to notch out feedback frequencies.

Reposition microphone or monitor to improve rejection. Change the acoustic relationship between them.

Distortion Problems

Check gain staging throughout the signal path. Clipping can occur at input, channel, bus, or output stages.

Reduce gain at the source. Input clipping sounds harsh and cannot be fixed downstream.

Verify pad switches are engaged for hot sources. Line-level signals into microphone inputs often need padding.

Check speaker and amplifier status. Distortion from overdriven speakers sounds different from mixer clipping.

Intermittent Signal

Intermittent problems usually indicate connection issues. Wiggle cables while listening to isolate the problem.

Check cable ends for cold solder joints or damaged connectors. Internal failures cause inconsistent connection.

Verify stage box connections are fully seated. Partially inserted XLRs can cause intermittent audio.

Replace suspect cables even if they work momentarily. Intermittent cables will fail again.

Low Level From a Channel

Check input gain setting. Insufficient gain produces quiet signal throughout the channel.

Verify source output. Some instruments or microphones have output level switches that affect signal strength.

Check for engaged pads or attenuators. These reduce signal and may have been activated unintentionally.

Confirm the correct input type (mic/line) is selected. Line input for microphones provides inadequate gain.

Phase or Thin Sound

Check microphone polarity on multi-mic sources. Out-of-phase microphones cause cancellation and thin sound.

Verify cable wiring. A cable with pins 2 and 3 reversed creates phase reversal.

Use phase reverse on the mixer to test. Flip phase on one of multiple microphones; if sound improves, keep that setting.

Consider microphone placement. Physical distance differences between mics create arrival time differences that affect phase.

Monitor Problems

Verify aux send routing and levels for the affected monitor. Check both channel send and aux master.

Confirm physical connection between aux output and monitor. The signal must actually reach the speaker.

Check powered monitor status—power, level controls, and signal indicators.

Test the monitor with a known-good signal. If it works, the problem is upstream in the monitor routing.

Staying Calm Under Pressure

Problems during performance require quick, calm response. Panic makes diagnosis harder; calm thinking solves problems faster.

Mute the problem source while diagnosing. Silence is better than noise or feedback while troubleshooting.

Have backup plans ready. Spare cables, backup microphones, and alternative routing provide options.

Communicate with the band if necessary. A brief pause beats continued problems.