| 摘要 |
A bass compensation circuit for use in a sound reproduction device is provided with a second-order positive feedback type high-pass filter. The filter has an operational amplifier and a first positive feedback resistor, a first variable resistor connected to an input terminal for receiving an input signal, coupled with a second variable resistor for volume control, and a second resistor for determining a Q-value and a cut-off frequency of a second-order positive feedback type high-pass filter. The first variable resistor and the second resistor are inserted in series between the first resistor and the ground. Thus, the bass compensation circuit can amplify only low frequency signals which do not serve as a masking sound used in masking middle and high frequency signals and has a low level when the sound volume is low. Moreover, the Q-value and the cut-off frequency of the second-order positive feedback type high-pass filter can continuously be changed by using the second variable resistor. Consequently, the Q-value and the cut-off frequency of the second-order positive feedback type high-pass filter can change in a natural manner against a change in sound volume.
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