This bass booster circuit is made using the quad op-amp ic LM324. This op-amp ic has 4 operational amplifier, but in this circuit only 2 op-amp is used. This circuit provide Low pass filter of input audio which produce a Low frequency of input and high frequency is blocked .
Connect the circuit as the given diagram as below . Give input through the 47K resistor at pin no 2 , one other 47 K resistor is connected between the pin 1 and pin 2. Pin 1 is the output pin of 1st opamp and this output pin is connected with 2nd op-amp input inverting pin 6 through resistors and capacitors . Pin no 4 is connected with +9v supply. pin 11 is connected with -9v and connect the ground with given terminals in diagram. Use dual power supply for operation of this circuit .RV1 is 100k preset for adjusting the level of frequency. Pin no 7 is the output of 2nd opamp and this pin is used in this circuit as the output also. Output must connected to amplifier input .