Gain Structure and Optimizing Levels

From Audacity Wiki

In short, when setting levels start with the strongest signal possible, and then try to avoid boosting the noise floor by applying gain to the signal in any subsequent stages such as pre-amplifier, channel/mixer output, audio interface or PC input. This is especially important after a particularly noisy stage, such as an old amplifier or poorly grounded circuits.

The noise floor is that small portion of the signal that is usually masked by the proportionately much larger desirable signal, yet which becomes more audible if overdriving signals, or cranking up the volume of poor signals. Start with a good strong signal, run it though balanced connectors, spread any gain changes out nice and evenly (across different stages), and you should be fine.

Good pre-amps offer both dynamic performance and good signal-to-noise specifications.

TBC