A system comprising: a delta-sigma analog-to-digital converter comprising: a loop filter having a loop filter input configured to receive an input signal and generate an intermediate signal responsive to the input signal; a multi-bit quantizer configured to quantize the intermediate signal into an uncompressed digital output signal; and a feedback digital-to-analog converter having a feedback output configured to generate a feedback output signal responsive to the uncompressed digital output signal in order to combine the input signal and the feedback output signal at the loop filter input; and a digital compression circuit (106, 106A) configured to receive the uncompressed digital output signal and compress the uncompressed digital output signal into a compressed digital output signal having fewer quantization levels than that of the uncompressed digital output signal, wherein for each given sample of the uncompressed digital output signal, the digital compression circuit is configured to generate a corresponding sample of the compressed digital output signal such that at least a first bit of the compressed digital output signal represents a first quantization level transition between the given sample and a first previous sample sampled consecutively previous to the given sample and at least a second bit of the compressed digital output signal, different from the first bit of the compressed digital output signal, represents a second quantization level transition between the first previous consecutive sample and a second previous consecutive sample sampled consecutively previous to the first previous sample, wherein the digital compression circuit is further configured to encode into the compressed digital output signal the first quantization level transition in dependence on a direction of the second quantization level transition. a loop filter having a loop filter input configured to receive an input signal and generate an intermediate signal responsive to the input signal; a multi-bit quantizer configured to quantize the intermediate signal into an uncompressed digital output signal; and a feedback digital-to-analog converter having a feedback output configured to generate a feedback output signal responsive to the uncompressed digital output signal in order to combine the input signal and the feedback output signal at the loop filter input; and a digital compression circuit (106, 106A) configured to receive the uncompressed digital output signal and compress the uncompressed digital output signal into a compressed digital output signal having fewer quantization levels than that of the uncompressed digital output signal, wherein for each given sample of the uncompressed digital output signal, the digital compression circuit is configured to generate a corresponding sample of the compressed digital output signal such that at least a first bit of the compressed digital output signal represents a first quantization level transition between the given sample and a first previous sample sampled consecutively previous to the given sample and at least a second bit of the compressed digital output signal, different from the first bit of the compressed digital output signal, represents a second quantization level transition between the first previous consecutive sample and a second previous consecutive sample sampled consecutively previous to the first previous sample, wherein the digital compression circuit is further configured to encode into the compressed digital output signal the first quantization level transition in dependence on a direction of the second quantization level transition.