A sigma-delta ADC (200A) uses blue-noise (random, pseudo-random) modulation (202) to reduce the effect of the substrate noise. Pairs of blue-noise multipliers (202) are placed before and after each non-delayed integrator (106). In the case of a sample-delayed integrator, the integrator is first separated into a non-delayed integrator (110) followed by the delay element (112). The multiplying sequence is a sequence of 1's and −1 's that has blue-noise spectral characteristics (i.e., the spectrum has a low frequency deficiency).