3-Band Active Equalizer Circuit using LF353 IC + PCB

PCB 3-Band Active Equalizer Circuit with LF353 IC

This three-band active graphic equalizer circuit is an active filter set for three basic audio equalization ranges, bass, mid and treble. The circuit is based on the LF353 operational amplifier integrated circuit.

The LF353 is a two-input JFET operational amplifier with an internally compensated input offset voltage. The JFET input device provides wide bandwidth, low input bias currents and offset currents.

⚙️ Features

• Internally Trimmed Offset Voltage: 10 mV
• Low Input Bias Current: 50pA
• Low Input Noise Voltage: 25 nV/√Hz
• Low Input Noise Current: 0.01 pA/√Hz
• Wide gain bandwidth: 4 MHz
• High slew rate: 13V / μs
• Low Supply Current: 3.6 mA
  
• High Input Impedance: 1012Ω
  
• Low Total Harmonic Distortion : ≤0.02%
  
• Low 1/f Noise Corner: 50 Hz
  
• Fast Settling Time to 0.01%: 2 μs
  

🛠️ Equalizer Circuit

The 3-band Equalizer use a Integrated Circuits operational amplifier LF353, and the capacitors determine the frequencies, the higher their capacitance, the lower the cutoff frequencies.

The proposed equalizer is a 2-octave graphic equalizer with a 3-band circuit, the cut-off frequencies are at: 150Hz, 1kHz and 12kHz.

This circuit was assembled with LF353, but nothing prevents you from using other replacement pin compatible ICs, such as: LM1558, RC4558, LM358 etc.

The recommended supply voltage is between ±11V and ±15V, but note that the maximum voltage IC supports is ±18V. The IC consumption current is 6.5mA maximum, and 3.6mA average.

The IC has two internal amplifiers, we get a amplifier for each frequency and the last one for the final amplification of the entire circuit. In Figure 2 below, the pinout and configuration of the LF353 integrated circuit is shown.

Fig. 2 - Pinout IC LF353

🔌 Circuit Schematic Diagram

In Figure 3 below, we show the complete 3-band equalizer circuit, and that you can download the files in option; Download files below at the bottom of the page.

Fig. 3 - Schematic Diagram 3-band Active Equalizer Circuit with LF353 IC

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🛠️ Component List

• U1 .............. Integrated circuit LF353
  
  
• R1, R2, R5, R6 ... 10K resistor (brown, black, orange, gold)
• R3, R7 ................ 3.6K resistor (orange, green, red, gold)
• R4, R8 ................ 1.8K resistor (brown, gray, red, gold)
  
  
• C1 ...................... 4.7uF electrolytic capacitor
• C2 ...................... 1uF electrolytic capacitor
• C3 ...................... 50nF polyester capacitor 
• C4, C6 ............... 5nF polyester capacitor
• C5 ...................... 22nF polyester capacitor
  
  
• VR1 .................... 47K Potentiometer 
• VR2, VR3 .......... 100K Potentiometer 
• VR4 .................... 500K Potentiometer 
  
  
• P1  ....................... Screw Terminal Type 5mm 3-Pin Connector
• P2, P3 .................. Screw Terminal Type 5mm 2-Pin Connector

• Others .................. PCB, tin, wires, etc.

🖨️ Printed Circuit Board (PCB)

To facilitate your assembly, we have made available the files for the Printed Circuit Board (PCB) designed specifically for this equalizer. The PCB has been carefully planned to minimize interference and ensure maximum signal quality.

The files are available in GERBER, PDF, and PNG formats, covering all your needs, whether for a homemade assembly or to send to a professional fabrication. The PCB layout follows the best practices of audio circuit design, with properly dimensioned tracks and strategic positioning of components.

📥 Direct Download Link

To download the necessary files for assembling the electronic circuit, just click on the direct link provided below:

Download PCB Files (GERBER, PDF, PNG)

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The ElCircuits Team ⚡