| 摘要 |
PURPOSE:To improve the data error rate at the inner circumferential side by providing a write clock switching circuit switching outputs of >=2 servo PLOs in response to a cylinder address in operation and a signal switching circuit to compress the bit density difference between the peripheral and inner circumference of a disc. CONSTITUTION:In reading data written on a data disc by using a write clock having a frequency different from inner and outer circumferences, a read output L of a write/read head 17 is amplified by a read amplifier circuit 12, a read main amplifier 13 amplifies further an output M of the preamplifier and outputs while pulsing digitally. The output N of the read main amplifier is inputted in parallel with read circuits 14, 15. When a servo head 4 is placed at a region 2, the read circuit 14 is actuated when the level of a control output line E is logical 1 to generate a clock having a frequency f1' synchronously with the output N of the read main amplifier, the output N of the read main amplifier is identified by using the timing to an output read clock P and a read data Q. This, it is possible to compress the bit density difference at inner and outer circumferences to improve the data error rate.
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