| 摘要 |
A tone control has a transfer function characterized by a zero and pole on the real axis spaced from the imaginary axis by an audible frequency with adjustment of a potentiometer causing one of the zero and pole to slide along the real axis while the other remains stationary. A treble control with fixed pole at 1 kHz from the imaginary axis has a potentiometer connected to an input terminal with its arm connected to an output terminal and is in series with a resistor and capacitor between the input terminal and ground. A bass cut control has a capacitor connected to an input terminal in series with a resistor between the input terminal and ground. The capacitor is shunted by a potentiometer having its arm connected to an output terminal. A treble tone control circuit with both cut and boost has a center tapped potentiometer with first and second opposed ends connected to + inputs of first and second operational amplifiers, each having a feedback connection with the - input. First and second capacitors connect the outputs of the first and second operational amplifiers, respectively, to the - input of a third operational amplifier. The series combination of first and second resistors connect the - input of the third operational amplifier to the + input of the first operational amplifier and the serial combination of third and fourth resistors connect the - input of the third operational amplifier to the + input of the second operational amplifier. There is a feedback connection with the output of the third operational amplifier to the junction of the first and second resistors. The wiper of the tapped potentiometer, the tap of the potentiometer and the + input of the third operational amplifier are connected to a common line.
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