| 摘要 |
PURPOSE:To protect clipping of a signal by providing a speaker circuit with the function that when the level of a signal applied to the speaker exceeds a predetermined value, motional feedback operation is stopped. CONSTITUTION:As the level of a signal applied to speaker 7 increases, sound volume to be discharged by speaker 7 is getting larger and the level of the detecting signal obtained by a detecting resistor 8 also increases. Further, when the level of the output signal from main amplification circuit 6 increases and the output level of rectification circuit 19 constituting a level detecting circuit 15 exceeds a predetermined value, a switching transistor 20 is reversed to the conductive state and a signal channel 22 for a detecting signal to an operating amplifier is grounded, so there is no detecting signal to be input to the operating amplifier 12, thereby eliminating a detecting signal to be input to an operating amplifier 3 constituting a mixing circuit 2. Thereby, a regenerating signal to be input to an input terminal 1 is amplified, applied to speaker 7, and discharged without increasing the level of low band frequency. |
