| 摘要 |
PURPOSE:To prevent howling of an acoustic equipment by providing a phase fluctuation control means controlling the operation of a phase fluctuation circuit, a peak value comparison means and a timer circuit and using the output of the timer circuit so as to control the phase fluctuation circuit. CONSTITUTION:A peak value comparison circuit 9 outputs a high level signal when the absolute values of two adjacent positive and negative maximum peak values outputted from a preamplifier 2 are nearly equal to each other. Every time an output of a peak value comparison circuit 9 rises from a low level to a high level, a timer circuit 10 sends a high level signal kept for a prescribed time to a switch circuit 7. The timing when the switch circuit 7 is turned on is equal to time when the peak value comparison circuit 9 detects a resonance frequency being the cause of howling. Thus, the shift angle of the phase fluctuation circuit 5 is not always started from 0 deg. but started at a random shift angle, then the suppression of the resonance is quickly ensured. |
