A branch metric calculation unit calculates a set of branch metric values for subsequent samples of the sampled input signal. Each of the set of branch metric values is an indication for the likelihood that an amplitude value of a sample corresponds to a particular state, a state being defined as a sequence of n-ary digits. A delay unit, which forms part of a delay chain of delay units, includes a first delay unit of the delay chain which is coupled to the branch metric calculation unit. A path metric calculation chain of path metric calculation units includes one or more path metric calculation units having first inputs coupled to a delay unit and second inputs coupled to a preceding path metric calculation unit. The path metric calculation unit calculates the path metric values from the branch metric values, a path metric value being on indication for the likelihood that a sequence of samples corresponds to a sequence of states.