BloodRosesAeolus, your daughter flies.Premium
Because you're modulating the attenuator on your pre-amplifier. At -99dB the signal was fully attenuated or 'restricted' if you will. At 0dB the pre-amp is no longer attenuated and is feeding your power amplifier the full signal. The final volume output is going to be based on the impedance load on your power amplifier and the sensitivity of your transducers or "speakers" if you will.