Today's Lesson

Let's have a quick little discussion about gain and signal. Every microphone that comes into your mixing console needs to be adjusted for an input gain appropriate for the audio source it is capturing.

Sources that are very quiet may require a more sensitive microphone to be used or higher preamp gain settings at the mixing console. If a source is too quiet or the gain is turned up too high, the microphone can pick up more energy from the room or loudspeakers than from the actual source you are trying to reinforce.

Properly selecting and positioning a microphone is very important, but even the “right” microphone in the “right” place can cause problems if the gain is set too high or if there is too much background noise and not enough energy from the intended audio source.

The technical term for this is “gain before feedback”. How much gain can I get out of the microphone before it starts to feedback?

It all depends on the variables just mentioned, plus another element called “signal-to-noise ratio” (SNR for short). The louder the signal and the quieter the noise, the better signal-to-noise ratio, and the least opportunity for feedback. FYI: To the microphone, the audio content from the loudspeakers is “noise” and the sound from the source is the true “signal” you wish to capture. Make sure your “signal” is louder than your “noise”.

Many instances of poor signal to noise ratio occurs when vocalists are too far off their mics. When a singer is not on their mic, I have to turn up the gain which invites more noise into the signal eventually causing feedback. So, encourage your vocalists to sing in close proximity to their mics.

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