A parametric equalizer in imported audio

It is a two-stage parametric equalizer circuit common in imported audio . The frequency ranges of these two sections are respectively, 32Hz ~ 450Hz and 450Hz ~ 10kHZo. In the two sections, a 50kfl potentiometer is used for continuous selection and adjustment of frequency. In each section, a set of 220kCZ double potentiometers are used to adjust each selection. Fine-tune at a certain frequency point. The fine-tuning double potentiometer uses a linear potentiometer to obtain uniform linear adjustment characteristics. The main amplifier of     this circuit uses a famous integrated operational amplifier CA3140, which is a well-known operational amplifier circuit . Characteristics as shown in the table