In an apparatus without a helical movement, a reconstruction error considerably increases as a radiation angle increases. At least a portion of the generated plurality of chip-rate synchronously sampled signals may be simultaneously equalized in time domain and in spatial domain. The evaluations may include, for example, hierarchically ranking the consumers andor determining a clustering of the consumers. The pedestals are formed in the area of the contact openings that will be etched in an overlying dielectric to form contacts to the wordlines. In particular, when the track jump command is input, a PLL of a wobble signal is inhibited, and a PLL-wobble signal is held to a previous value obtained before the track jump is performed, during the track jump, or a header mask signal is generated using a read channel signal which is not influenced by a wobble period, until a wobble signal becomes stable after a trackjump.