This work proposes a novel structure for adaptive sigma delta modulation that leads to considerable improvement in the dynamic range of the modulator. The quantizer step-size is adapted based on estimates of the input signal to the quantizer block rather than on estimates of the input signal to the modulator itself, as is common in current schemes. The proposed structure can be implemented rather directly by means of analog switches. Theoretical and simulation results show considerable improvement in SNR performance, especially for small amplitude signals, over existing adaptive sigma delta modulators.