Electronic balanced subwoofer circuit

The electronically balanced subwoofer circuit uses two quad operational amplifiers. High-speed operational amplifiers such as TL084 can be used. The circuit is shown in Figure
9-680. The left and right channels are mixed through R1 and R2. R1 is the bass total level adjustment potentiometer (for number type). Al is a buffer amplifier. A2 forms a second-order high-pass filter with a turning frequency of 20Hz. It filters out the sub-bass signal
outside the audio frequency band. Where and ~ form the key part of this circuit - the near-resonance equalization circuit. A3 forms a multi-terminal negative feedback active Second-order band-pass filter , center rate is 20Hz, signals below 20Hz are attenuated with a slope of 12dB per octave. ~ Together with Rg, Rio, and G, it forms a bass boosting network 1. Starting from about 220Hz, it boosts the bass with a slope of 3dB borrowing frequency range. From 7Hz, Liu 2, 2, and OHz, it improves a total of 30dBoRr and Di and ~ to form an inverting adding circuit . A2 output Adding the bandpass increases the amount of improvement at 20№ and the balanced response is smoother.