According to one embodiment, a magnetic disk device includes: a disk; a head including a main magnetic pole, a write shield that faces the main magnetic pole in a first direction and is separated from the main magnetic pole by a gap, a first assist element that is disposed in the gap and a second assist element that is disposed in the gap and is positioned relative to the first assist element in a second direction intersecting the first direction; and a controller configured to: cause a first assist energy from the first assist element to be applied to the disk and affect a coercive force of the disk; and cause a second assist energy from the second assist element to be applied to the disk and affect a coercive force of the disk, wherein the first assist energy is different from the second assist energy.

A hard disk drive includes multiple actuator assemblies, each of which includes a head-stack assembly (HSA) including an end-arm to which a single head-gimbal assembly (HGA) is coupled, where this end-arm is configured with a notch along one side and a triangular or quadrilateral-shaped through-hole at a root-side of the end-arm, and where the HSA further includes a plurality of other end- and inner-arms to each of which two HGAs are coupled and none of which have a through-hole near their root. The single-HGA end-arm may be further configured with an outer damper having a through-hole coincident with the end-arm through-hole, such that the through-hole of the end-arm is not covered by this damper, and an inner damper having no through-hole, such that the through-hole of the end-arm is covered by this damper. Gains are thereby better matched across all HGAs for problematic arm and system modes.

A method to determine a relative delay between a current-overshoot signal and a write data signal for a hard disk drive preamplifier, the method including using a memory element to strobe a test current-overshoot signal with a test data signal; counting a number of strobed transitions of the test current-overshoot signal; adjusting the delay based on the number of strobed transitions; setting a phase difference between the current-overshoot signal and the write data signal according to the delay; and using the memory element to strobe the current-overshoot signal with the write data signal.

A method for manufacturing a disk device includes the steps of measuring a first gain of a control signal of a fine motion actuator while positioning a head to a first radial position of a disk medium using a coarse motion actuator but not the fine motion actuator, based on an auxiliary servo pattern recorded on the disk medium, measuring a second gain of a control signal of the fine motion actuator while positioning the head to a second radial position of the disk medium using the coarse motion actuator but not the fine motion actuator, based on the auxiliary servo pattern recorded on the disk medium, and determining gain correction values which are to be applied to a control signal for the fine motion actuator while performing servo pattern writing on the disk medium, based on the first and second gains.

According to an embodiment, there is provided a disk device including a disk, a head, a preamplifier and a controller. The head writes information to the disk according to a write current. The preamplifier causes the write current to flow through the head. The controller is capable of causing the preamplifier to perform current zero control for maintaining an amplitude of the write current at zero, and is capable of changing a time for maintaining the amplitude of the write current at zero according to a pattern of write data.

Systems and methods of digital automatic power control are presented. A preamplifier circuit may include a digital-to-analog converter (DAC) circuit to sample a power signal, such as a from a laser power monitor. The preamplifier may store the sample in an internal preamplifier memory. The sample may be utilized to update a current output of the preamplifier that affects the power signal. These systems and methods may be particularly useful for lasers and heat-assisted magnetic recording (HAMR), which may be utilized during a read mode or a write mode of a HAMR data storage device.

Method and apparatus for enhancing write current switching efficiencies during data write operations in a data storage device. In some embodiments, write data are described in the form a sequence of symbols of nT length where T is a channel clock rate and n is an integer over a selected range. Bi-directional write currents are applied to a write element to record the sequence of symbols to a storage medium. The write currents are switched between a first rail current and a second rail current for alternating symbols. The write currents are further transitioned to an intermediate current value for at least one channel clock period immediately preceding a next occurrence of a symbol boundary between an adjacent pair of symbols in the sequence.

A data storage device is disclosed comprising a disk, a head for accessing the disk, and a sensor for generating an alternating sensor signal. The sensor is disconnected from an input of a sensing circuit and while the sensor is disconnected an alternating calibration signal is injected into the input of the sensing circuit, wherein the alternating calibration signal comprises a predetermined offset and amplitude. A response of the sensing circuit to the alternating calibration signal is evaluated to detect at least one of an offset and a gain of the sensing circuit.

In one embodiment, a system for processing data includes a processor and logic integrated with and/or executable by the processor. The logic is configured to detect and track positive peak amplitudes and negative peak amplitudes of a readback waveform during data reading using a tracking threshold module, and to detect and track positive peak amplitudes and negative peak amplitudes of the readback waveform during the data reading at an input to an equalizer using a second tracking threshold module in response to reading a data set separator (DSS). Moreover, the logic is configured to perform asymmetry compensation on the data using an asymmetry compensator in an asymmetry compensation loop based on input from the tracking threshold module when not reading a DSS and based on input from the second tracking threshold module when reading a DSS, an output of the asymmetry compensator being provided to the equalizer.

Disclosed are a two-stage audio gain circuit based on analog-to-digital conversion and an audio terminal. The two-stage audio gain circuit includes a PGA configured to receive an analog audio signal and perform programmable gain amplification processing on the received analog audio signal; an ADC configured to convert the analog audio signal after the programmable gain amplification processing into a digital audio signal and output the digital audio signal; a first AGC gain unit configured to perform a first AGC processing on the digital audio signal and output a first gain adjustment value to the PGA, for the PGA to perform gain adjustment on the received analog audio signal; and a second AGC gain unit configured to perform a second AGC processing on the digital audio signal and output a second gain adjustment value to the PGA, for the PGA to perform gain adjustment on the received analog audio signal.