Equalizer (a) composed of TL084

It is a dual five-band graphic equalizer circuit composed of an integrated operational amplifier TL084. Now take the L channel as an example to analyze
its working principle. This circuit uses an adjustment potentiometer connected to the inverting and inverting input terminals of the op amp.
    The principle is shown in Figure 4-35(a). Now compare and analyze: the operational amplifier Ai forms a common amplifier , and the five operational amplifiers A3 to Aii
form a balanced network with center frequencies of 100H, 330Hz, 1X7, 3.3kHz, and 10kfk respectively. Analog inductor. In
the circuit, C9.C14, C19.C25, C31 are equivalent to Cl; cll, C16, C21, C27, C33 are equivalent to Q; attenuation
resistors R14, ‰, ‰, R3z, R38 are equivalent to Ri; Rl5, Rzt , Ai, R33, R are equivalent to the feedback resistor R2.
    In Figure 4-35 (a), five potentiometers RPi~RPs are connected between the non-inverting and inverting input terminals of the common amplifier. When
the sliding point of the potentiometer is upward When moving squarely, the fo component in the input signal is
divided by the series resonance network composed of Ri, analog inductance and cl. At the same time, the feedback coefficient of the amplifier circuit increases, the amplifier gain decreases, and fo is attenuated. When the potentiometer
's slide point moves downward, the opposite occurs, so fc is raised. When the sliding point of the potentiometer
is in the middle position , the amplifier neither attenuates nor improves, and the amplifier is in a flat amplification state.