Abstract: According to one embodiment, a head position demodulating method and a magnetic disk device switch a demodulation window such that an amplitude of a fundamental wave component of a null-type burst pattern transitions from a decreasing direction to an increasing direction along with an increase in seek speed during demodulation of the null-type burst pattern recorded on a magnetic disk.

Abstract: According to one embodiment, a head position demodulating method and a magnetic disk device switch a demodulation window such that an amplitude of a fundamental wave component of a null-type burst pattern transitions from a decreasing direction to an increasing direction along with an increase in seek speed during demodulation of the null-type burst pattern recorded on a magnetic disk.

Abstract: A digital filter can de-emphasize pre-emphasized signals without an extra processing routine or hardware. Via a second bus 21, a decision unit 19 receives a record status signal out of digital audio signals input by an input-output unit 24, thereby checking whether or not the received signals have been pre-emphasized. When the signals have been pre-emphasized, the decision unit 19 selects a set K2 of multiplication coefficients (a.sub.0, a.sub.1 and a.sub.2). Otherwise, the decision unit 19 selects the other set K1 of multiplication coefficients (-1, 0, 0). In the former case, the input signals are de-emphasized. In the latter case, a transmission function is "-1", so that the input signals are multiplied by "-1", i.e. no de-emphasizing process is carried out.