Simple 3 Band Audio Equalizer Circuit

This 3 band audio equalizer circuit is like a tiny knob controller for your music.

It lets you adjust the amount of bass low sounds, midrange voices and instruments and treble high sounds to customize the music to your liking.

This way, you can make your music sound exactly how you want it depending on the kind of music you are listening to or the room you are in.

Circuit Working:

Parts List:

This active filter network utilizes an LM358 op amp from national semiconductors to create a 3 band equalizer circuit for bass, mid and high audio frequencies.

The LM833 op amp is chosen for its low noise, wide bandwidth and high slew rate characteristics.

The circuits output is intended to be DC coupled but slight DC variations across the 100k potentiometers at the op amp A2 feedback lines may require a coupling capacitor.

Here are the technical specifications for this 3 band equalizer:

• Bass range cutoff frequency: 200 Hz
• Midrange is a bandpass network centered at 1 kHz
• High range cutoff frequency: 2 kHz

The maximum equalizer range is approximately 15 dB.

At the midpoint of the potentiometer noise attenuation is around 90 dB, with a bandwidth of 1 MHz and a gain of 0 dB.

The gain can be adjusted using R2 with the formula mentioned below.

Formula:

Knowing the Gain Formula for the 3 Band Audio Equalizer Circuit:

Usually, an operational amplifier is used in a non inverting amplifier design when the below formula is used.

R1 and R2 are positioned as follows in this context:

R1 is linked between the op amps ground and inverting input.

The non inverting input and the op amps output are linked via R2.

Vu = R2 / R1

where,

• R2: Usually a variable resistor (potentiometer), this resistor lets you change the amplifier stages gain.
• R1: This resistor is fixed and functions as a complement to R2 in determining the gain.
• Vu: This stands for the amplifier stages voltage gain.

In our circuit diagram the general formula will be :

Vu = R3 / R2

This formula can be used to calculate the gate of op amps.

How to Build:

To build a Simple 3 Band Audio Equalizer Circuit follow the below mentioned assembling steps:

• Ensure you have all the required components listed above.

Circuit Assembly

• Place the LM358 op amp on the PCB.
• Connect the power supply to the op amp pins pin 4 and pin 8 typically for positive and negative supply.
• Connect the pin 3 of IC to the ground.
• Connect the components according to the schematic provided using the appropriate resistor, capacitor and potentiometer values for each part of the circuit.
• For each band bass, mid, high connect the input signal to the respective potentiometer P1, P2, P3, and connect the output of each band to the summing point the junction of R7, R8, and R9.

Testing

• Once the circuit is assembled connect an audio source e.g. a music player to the input of the equalizer.
• Connect an amplifier or headphones to the output of the equalizer.
• Power on the circuit and test the equalizer by adjusting the potentiometers for each band to see the effect on the audio output.

Adjustments

• Fine-tune the values of resistors, capacitors and potentiometers to achieve the desired frequency response and gain for each band.
• You may need to use an oscilloscope or spectrum analyzer to visualize the frequency response and make precise adjustments.

Note:

• Building electronic circuits requires basic knowledge of electronics and soldering skills.
• If you are not familiar with these, it is advisable to seek assistance from someone with experience.

Conclusion:

A simple 3 band audio equalizer circuit can be constructed using operational amplifiers, resistors and capacitors to adjust the levels of bass, midrange and treble frequencies in an audio signal.

By selecting appropriate component values, specific frequency ranges can be targeted for adjustment allowing for customization of the audio output to suit different preferences or requirements.

References:

Datasheet IC LM358

3 band audio equalizer circuit transfer function