As with all microphone pre-amps, the lower you set the gain on the Mic2496, the lower the mic pre-amp noise that you'll record.
We designed the Mic2496 with concert recording (and not, for example, quiet dialog) as its primary application. We designed around the sensitivity specifications of two fine miniature microphones: DPA's 4060 and 4061 (as used in our High End Binaural microphone sets). With the DPA 4060 (20mV/Pa), our customers can record loud concerts with the Mic2496's level controls at near minimum, and moderately loud concerts with the levels turned up only a bit. With the 4061s (6 mV/Pa), they can record extremely loud concerts with the level controls at near minimum. For quiet recordings, the target was DPA's 4003 (40mV/Pa) -- its high sensitivity allows Mic2496 to use low gain settings and provide fine S/N performance.
When you select microphones to use with the Mic2496, you should choose microphones that have sensitivity specifications similar to above three microphones. If you choose to use a low sensitivity microphone (e.g., a ribbon mic or a dynamic mic like a Shure SM-57), you'll have to turn up Mic2496's level controls near maximum and will hear more background noise.