An apparatus comprises read channel circuitry and signal processing circuitry associated with the read channel circuitry. The signal processing circuitry comprises a detector and a decoder coupled to the detector. The detector is configured to perform fixed-point detection on a digital data signal using a first set of quantization levels determined based at least in part on a result of a floating-point detection of the digital data signal. The decoder is configured to perform fixed-point decoding on an output of the detector using a second set of quantization levels determined based at least in part on a result of a floating-point decoding of the output of the detector.