| 摘要 |
PURPOSE:To execute a reproduction faithful to an original signal, and also to eliminate a noise surely in case of switching a head by controlling a response time of a phase synchronizing means in acordance with a switching timing of a switching means. CONSTITUTION:FM modulating audio signals of input terminals 1, 2 are synthesized by a switching circuit 3, and supplied to an input of a phase comparing circuit 11 through a BPF 4. The circuit 11, a VCO 12 and an LPF 13 constitute a phase synchronizing loop PLL, an output signal of the VCC 12 is phase-locked to a reproduced FM modulating audio signal inputted to the circuit 11 and inputted to an FM demodulator 5, and a detected audio signal is outputted to a sound signal output terminal 10 through an LPF 6. On the other hand, a signal of (b) is supplied to a head switching pulse input terminal 8, a signal of (c) is obtained in an output of a time constant variable pulse generating circuit 14, and in accordance with it, a time constant varying circuit 15 operates so that a response of the PLL is delayed for a constant interval of time from a head switching time. Accordingly, the generation of a large amplitude noise of the reproduced FM modulating audio signal is suppressed, and also a reproduction faithful to the original sound can be executed. |
