ADC circuitry has a first programmable gain amplifier to amplify an analog input, a first analog to digital converter coupled to an output of the first amplifier, a second programmable gain amplifier, to amplify the analog input, a second analog to digital converter coupled to an output of the second amplifier, and a digital circuit for deriving a digital output from the outputs of the first and second converters and a controller for controlling the gains of the first and second amplifiers, according to the outputs of the first and second converters. Such programmable gain pre amplifiers help enable effective dynamic range to be extended without unduly increasing the number of quantisation bits, or the number of components or the power dissipation. It can be used in applications sensitive to size and power, such as DSP based acoustic devices including hearing aids.