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Taking the following basic audio signal chain...

singer -> microphone -> audio interface preamp

I understand that if a vocalist sings very softly into the microphone, the desired signal would be relatively "closer" to the mic's internal self noise level, compared to the same vocalist singing at a louder volume. This means that there would be a lower signal to noise ratio for the soft singing, which would be emphasized further by any gain applied later on during the preamp stage. I also understand that each new component added into the audio signal chain will produce its own "new" self noise and contribute additively to all the past noise leading up to it.

Question: What I am curious about is whether or not a preamp's internal self noise level is also boosted as gain increases, or if it remains constant across all gain percentages (whether 0%, 10%, 50%, 100%, etc gain). My initial thought is that this would depend on whether or not a preamp's self noise acts as an input to its own internal gain staging or if its self noise is simply a byproduct (output) of the gain staging itself (and thus consistent across all levels of applied gain percentages). Any insight is greatly appreciated, thanks.

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  • You wrote, "there would be a higher signal to noise ratio for the soft singing." You've got it backwards. If there's less 'signal' for a given amount of self 'noise', the ratio is lower. May 3 at 11:24
  • Btw, "...and contribute additively to all the past noise leading up to it" - it's not really as simple as that, as with non-correlated noise, there may not be any increase in the noise floor level.
    – n00dles
    May 3 at 14:02
  • The answer depends on the circuit design of the preamp and also 90%+ of the time doesn’t matter. Unless you’ve got a great room and a bad mic and/or preamp, room noise is going to be louder than self noise. May 11 at 12:01

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