Gain structure

Every audio signal passes through several stages between a microphone and a loudspeaker, and each stage has a level at which it works best. Gain structure is the practice of setting each one so the signal sits comfortably in that window all the way through.

The window exists because there are two walls. Too little level and the signal sits near the noise floor, so raising it later raises hiss along with it. Too much and the stage runs out of headroom and clips, which is heard as a hard, brittle edge that no amount of equalisation afterwards will remove.

The common mistake is fixing a quiet channel at the fader instead of at the input. Turning a fader up does not improve a signal that arrived too small; it amplifies the noise with it. The level is set at the head of the chain — the preamp — with the fader left near its neutral position, which is also where it has the finest control.

On a live show this is done during line check, one input at a time, with the person actually speaking rather than tapping the microphone. A talker check that lasts ten seconds per channel is why a system comes up clean when the room fills, and why the one channel that was skipped is the one that misbehaves.

Event audio production — owned inventory, our own crew, and a site survey before anything is specified.

• Front of house (FOH) The mix position out in the room where the engineer sits, and the audio the audience actually hears — not a department, and not a place a venue should treat as spare seating.
• DI box The small box that turns an instrument or laptop output into a balanced signal a long cable can carry — the unglamorous part that stops a hundred-foot run from humming.
• Monitor wedge The angled loudspeaker on the deck pointed back at a performer — the oldest way to let somebody hear themselves, and the one that sets the ceiling on how loud a microphone can go.