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Does microphone preamplifier gain increase the proximity effect?

Can the gain control on your preamplifier increase bass boost due to the proximity effect? Can it increase the level of acoustic background noise in your room?


Here is a comment from an Audio Masterclass student, sent in with his practical assignment work...

"I ended up adding +6db on my track fader before bouncing because I felt like increasing the gain on my mic interface was increasing the proximity effect, making me back up more and increasing room reflections. Not sure if gain works that way?"

In controlled studio conditions, there is no reason why you should not record with peaks bobbing up above -6 dBFS. There is no harm even in going all the way up to the top, but you have to pay close attention to make sure there are no red lights.

We often find however that students are reluctant to apply enough gain and they let their recording levels hover around -20 dBFS. The reason they give is pretty much always the same - "When I increase the gain, I can hear more background noise."

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Well yes, if you apply 6 dB more gain you will hear 6 dB more background noise. But you will have 6 dB more signal too, so everything is in proportion. The noise level has not increased relative to the level of the wanted signal. If you also reduce the monitor level by 6 dB, both signal level and noise level will be back exactly as they were before.

The gain setting you choose should be determined by the amount of headroom you want in your recording. If you are recording in controlled conditions and you want to extract absolutely as much audio quality as possible, then you will record as near to the top of the meter as you can, but keeping an eagle eye on those red lights. If you are recording in uncontrolled conditions - an interview in the street for example, then you need more headroom. You will follow a more BBC-like approach and let your levels bob around -18 dBFS, peaking up to -10 dBFS. That way you have 10 decibels of headroom in case your interviewee suddenly becomes more strident.

This applies to the proximity effect too (which is where low frequencies increase in level when a directional microphone is used very close to the sound source). Increasing the gain may make it seem that the proximity effect is intensified. But if you lower the monitor level to compensate, you will see that there is absolutely no difference.

The moral: The closer your peaks are to 0 dBFS, the higher the quality of the recording. But you may choose to peak at a lower level to allow more headroom for an unexpected rise in the level of the sound source.

There is no reason to use a low gain setting other than for increased headroom.

By David Mellor Monday August 5, 2019