a waveform equalizing filter unit includes a waveform equalizing filter with a plurality of taps each having a unitary delay element and a coefficient multiplier , a clock switching circuit for selecting a clock signal from at least two different frequencies , with the selected clock signal being fed to each of the unitary delay elements of the waveform equalizing filter , and a control circuit for selectively switching the tap coefficients of the coefficient multiplier in the waveform equalizing filter based upon which one of the different clock signals has been selected . a signal time adjuster is further included in a stage situated before the waveform equalizing filter that receives the input signal prior to being fed to the waveform equalizing filter to adjust the timing of the input signal in synchronism with the operation of selecting one of the different clock signal frequencies .