| 摘要 |
PURPOSE:To always listen by a constant audible sense without being influenced by magnitude of sound volume by executing automatically a loudness control confirming with a human audible sense characteristic. CONSTITUTION:A signal applied to an input terminal 5 is amplified by a main amplifier 4 and is fetched from an output terminal 6. An output of the main amplifier 4 is detected by a level detecting circuit 1. A voltage controlling circuit 2 supplies control voltage corresponding to a detecting level to an equalizing circuit 3. The equalizing circuit 3 has a presetting circuit for selecting in advance a reference loudness curve to an output voltage level. By this circuit 3, said output is converted to a characteristic corresponding to the reference loudness curve, and is added to an input signal by an adder 7. In case the output voltage from the output terminal 6 is large, equalized signal voltage is small. On the other hand, when the output voltage becomes small, the output characteristic approaches a characteristic whose high band and low band are emphasized by the equalizing circuit 3. |
