JPS6413248A - Revolution control system for drum - Google Patents

Abstract

PURPOSE:To shorten time required till a phase is locked by making a device into such constitution that the relation between the positions of a head and a tape in a standard timing till a drum reaches a constant velocity revolution is controlled as the gain of a phase servo circuit being made large. CONSTITUTION:In a play operation, the gain of an amplification circuit AMP is made large by inputting a signal GS, a gain control circuit GNC generates, and a phase difference discrimination circuit PDC makes a signal PS, corresponding to a phase difference for a head tape relative position signal HC, into the large gain by the AMP, and it is summed by an addition circuit SUM together with a velocity control signal VCS, and it drives a drum motor DMT through a driver DMD. The lock of a phase is detected by a monitor circuit PMC, and on the generation of the signal PLK, the circuit GNC returns the gain of the AMP to a steady state, and the drum maintains stably the constant velocity revolution and the phase lock. Accordingly, the time require till the phase is locked can be shortened, and the time till a sound is produced or the device comes to a state that recording is possible can be shortened.