Abstract: Signal processing system for reducing error due to intersymbol interference and other noise, the system having a feedforward equalizer adaptively responsive to a first error signal (e.sub.n) and having a noise decorrelator adaptively responsive to an adjusting signal (q.sub.n) derived from the first error signal. In a preferred embodiment the source of the signal (S.sub.n) is a magnetic disk having encoded data thereon. The feedforward equalizer reduces intersymbol interference. A decision device connected to the feedforward equalizer is coupled to connect the signal (X.sub.n) from the feedforward equalizer into a stream (d.sub.n) of data samples having a limited number of predetermined signal levels. The first error signal is the difference between signal levels of data samples in the stream and the output of the feedforward equalizer. The first error signal is utilized to adjust the feedforward equalizer and to provide an input to the noise decorrelator.