Level-crossing (LC) analog-to-digital (A/D) converters can efficiently sample certain classes of signals. An LC A/D converter is a real-time asynchronous system, which encodes the information of an analog signal into a sequence of nonuniformly spaced time instants. In particular, this class of A/D converters uses an asynchronous data conversion approach, which is a power efficient technique. In this study, the authors propose adaptive and multi-level adaptive LC sampling models as alternatives to conventional LC schemes and apply an iterative algorithm to improve the reconstruction quality of LC A/D converters. This simulation results show that multi-level adaptive LC outperforms conventional A/D converters such as sigma-delta A/D converters in terms of performance and computational complexity.