| 摘要 |
<p>PURPOSE:To faithfully reproduce a sound regardless of the frequency and the level of an input signal by always detecting the moving quantity of a voice coil oscillating according to the input signal, correcting the input signal according to the difference signal between the detected signal and the level of the input signal, and decreasing the difference signal. CONSTITUTION:A measure 50 of a wound coil bobbin 6 of a voice coil 10 is attached. Further, a photodetector 51 is attached to the lower surface of a ball piece 2 so that the detector 51 can be confronted with the surface of the measure plate 50, and a detecting part 351 is composed. Detected data 27a as a signal based on an optical signal to be outputted from the detecting part 351 are latched by a latch circuit 26 synchronously with a DEN bar pulse and inputted to a digital signal processor 23. In the processor 23, the detected signal 27a and the level of the input signal are compared, and when the difference signal is generated as the result of the comparison, correction for decreasing the difference signal is executed, and after that, the compared result is outputted to a latch circuit 25.</p> |
