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I've read a lot about gain when you have multiple inputs, it's best in a digital setup to keep it well under 0.

I can't find anything about a single input though, which is what I'm recording for some instructional videos.

My mic is only giving me an average of -30dB, much lower than the ideal -18dB. So the volume or gain need increasing.

If I only have a single input, is there any difference between boosting gain when recording, and just increasing the volume in my editing program (DaVinci Resolve)?

Is 1 better, or how are they different?

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Gain is more technical and can be discussed and measured in specific terms. Volume isn't really an appropriate term in mixing. It relates more to final amplification. There's no good way to relate one volume level to another. Sound pressure level is what's usually meant when people speak of volume.

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  • OK let me rephrase. Is there any difference to the quality of the output whether I raise gain on the input of a single source in software (OBS), or increase the ‘volume’ in the clip in DaVinci Resolve?
    – niico
    Sep 8 '20 at 9:08
  • As @IanBell points out, early gain is better than later gain, because late-stage gain amplifies both the original signal and any added noise. Within clipping limits, you're better served by higher signal levels throughout the chain, because any later reduction will also reduce noise.
    – Jim Mack
    Sep 8 '20 at 16:12
  • Thanks. I'll rephrase what you said to see if I understand. You're saying it's better to get more signal and more noise at the start, because you can filter the noise later and you're left with more signal?
    – niico
    Sep 10 '20 at 6:11
  • @niico - It's not about filtering, just levels. If your end goal is to have a signal of level X, starting with level XXX, then any noise picked up along the way will be reduced by 2/3 when you lower the original signal (+noise) from XXX to X. If you start with X, intending to get to XXX, then any noise introduced will be increased by a factor of 3 when you raise the signal (+noise) from X to XXX
    – Jim Mack
    Sep 10 '20 at 15:16
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Once you record, the achievable signal to noise ratio becomes fixed. So, if you increase the volume on playback you also increase the noise. In general it is better to increase the gain of the mic pre so the recorded level is -18dBFS in order to maximise the signal to noise ratio.

Cheers

Ian

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  • Thanks. I'm increasing gain in OBS software though, wouldn't that also increase noise? I can't get my lav mic (Rode Smartlav+) to get to -18dBFS by itself, I need to add a gain filter in OBS to get there. Is it OK that my lav doesn't get there by itself? Is it normal / OK to increase gain in software?
    – niico
    Sep 8 '20 at 9:09
  • Any gain change in software will not improve the signal to noise ratio; it will simply raise the signal and the noise by the same amount. Gain usually refers to the analogue part of the signal chain. What input interface are you using?
    – Ian Bell
    Sep 9 '20 at 11:38

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