A receiver structure recently proposed for the detection of pulse-amplitude modulation (PAM) signals is considered. The receiver is designed to reduce the complexity of the Viterbi decoder by equalizing the channel to an optimum desired short memory channel. Expressions for the optimum prefilter and short memory model are given. It is also shown that the minimum mean-square error achievable is a monotonic decreasing function of the model memory length. Numerical results for a specific channel are presented verifying this. A numerical investigation of the effect of shifting the reference tap is also included.