Line Check Basics: Verifying Signal Flow Before Soundcheck

Line check basics form the foundation of professional live sound practice. Before musicians play at performance level, before EQ adjustments, before monitor mixing begins, verifying that every signal reaches its intended destination prevents embarrassing gaps and troubleshooting during actual soundcheck.

Purpose of Line Check

Line check confirms signal flow without requiring full performance. Each input should reach its assigned mixer channel with appropriate level and without obvious problems. This verification step catches issues that would otherwise delay soundcheck or, worse, appear during performance.

Separating line check from soundcheck respects musicians’ time. They arrive ready to play, not to wait while engineers troubleshoot missing signals. Completing line check before musicians take positions allows immediate productive soundcheck work.

Line check also familiarizes engineers with the system before time pressure intensifies. Tracing an intermittent cable when the band waits impatiently differs from troubleshooting calmly during load-in.

Preparation Before Line Check

Complete physical setup before line check begins. Speakers positioned, cables run, mixer configured, and power applied throughout the system. Verify the system passes audio by playing reference material through the mains.

Prepare an input list documenting which source connects to which channel. Standard formats list channel number, source description, microphone type, and special notes. Having this reference prevents confusion about which signal should appear where.

Set mixer channels to reasonable starting positions. Gains at minimum, faders down, EQ flat, and auxiliary sends at zero. Phantom power off until condenser microphones connect and verify they need it.

Microphone Line Check Technique

Work through microphone inputs systematically, typically following the input list order. Speak into or tap each microphone while watching the corresponding mixer channel meter.

For vocal microphones, speak clearly into the capsule: “Vocal one, check. Vocal two, check.” Confirm signal appears on the expected channel with reasonable level. The visual meter indication suffices—full audio monitoring through the PA is unnecessary for basic line check.

Drum microphones check by tapping the shell near the microphone or speaking into the mic. “Kick drum, check. Snare, check.” Each microphone should respond with appropriate signal level.

Listen through headphones or at low main volume if problems appear. No signal, wrong channel, excessive noise, or distorted signal all indicate problems requiring attention before proceeding.

Direct Input Line Check

Instruments connecting through direct boxes require DI verification in addition to microphone checks. Connect the instrument, engage appropriate DI settings (pad, ground lift as needed), and produce signal from the source.

Bass guitar line check involves playing a few notes while confirming signal reaches the expected channel. Acoustic guitar and keyboard inputs check similarly. Active DI boxes require their power source—battery or phantom power—before producing output.

Line-level sources like keyboard outputs, backing track players, and electronic percussion modules connect directly to mixer line inputs. Play brief content from each source to verify signal flow.

Stereo sources require checking both channels. Left and right should reach their assigned mixer channels without swap. Playing stereo content with distinct left/right material confirms correct routing.

Troubleshooting During Line Check

No signal on a channel indicates a break in signal flow somewhere. Trace the path systematically: is the microphone connected? Is the cable intact? Is the snake channel working? Does the mixer input respond to other sources?

Substitution identifies faulty components. Try a known-good microphone on the suspect channel. If it works, the original microphone or its cable is faulty. If it fails, the problem lies downstream in the snake or mixer.

Excessive noise suggests grounding problems, faulty cables, or interference. Unplugging inputs to identify which source contributes noise narrows the search. Ground lift switches on DI boxes often resolve hum issues.

Weak or distorted signal may indicate incorrect input type selection (mic vs. line), phantom power status for condensers, or pad switch position for hot sources. Verify input configuration matches the source characteristics.

Efficiency Techniques

Work in logical order rather than randomly jumping between inputs. Sequential channel checking maintains organization and catches skipped inputs.

Use a talk-back microphone if available to communicate with stage hands positioning microphones. Clear communication speeds the process when multiple people are involved.

Mark confirmed channels to track progress. A piece of tape on checked faders, checkmarks on the input list, or digital mixer scribble strips indicating verified status all prevent rechecking completed channels.

Note problems for later attention rather than stopping to fix everything immediately. A complete picture of all issues enables efficient troubleshooting rather than serial problem-solving.

Digital Mixer Advantages

Digital mixers with saved scenes can recall previous show configurations, including input routing. Recalling a saved show instantly configures all channels according to the saved state.

Metering displays on digital mixers show all channel levels simultaneously. A glance across the meter bridge reveals which channels are receiving signal without individually selecting each.

Talkback and communication features on professional digital mixers simplify coordination between FOH position and stage. Engineers can speak with stage crew without leaving the mixer.

When Musicians Arrive

Complete line check means musicians can begin soundcheck immediately. Each position should be ready for performance-level playing with signals flowing correctly to the mixer.

Brief musicians on any known issues. “The second vocal microphone is slightly hot, I’ll need to set gain carefully” prepares them for potential adjustments during soundcheck.

Transition smoothly from line check to soundcheck. The groundwork is complete; now the creative work of building the mix can begin efficiently.