Systems and techniques relating to interpreting signals on a noisy channel. A direct current (DC) correction can be applied to an input of a post processor outside of a main read path that supplies data detector output to the post processor. A signal processing apparatus can include a data detector, a post processor responsive to an output of the data detector, and one or more DC control units configured and arranged to apply a first DC correction to an input of the data detector and a second DC correction to an input of the post processor, wherein the second DC correction is different from the first DC correction.