This is the marketing claim on the preamps:
"The PR-4 features the brand new ReGain Preamps™, ultra-quiet microphone preamps that deliver up to 60 dB of gain, providing enough amplification to drive even demanding dynamic microphones without the need for external inline boosters.
"Achieving an Equivalent Input Noise of -127 dBV (-125 dBu) represents a significant engineering accomplishment for the PR-4’s preamp design. Measured under A-weighted conditions at 60 dB gain with a 150 ohm source, this level of performance places the PR-4 firmly in professional territory, delivering an exceptionally low noise floor that preserves detail and clarity even with low-output microphones."