Low Pass Filter Circuit 4558 Subwoofer Preamplifier


A low pass filter circuit is an essential component in audio systems, especially when it comes to subwoofer preamplifiers. It effectively filters out high-frequency signals, allowing only low-frequency signals to pass through, thus producing a clearer and more defined bass output. One popular subwoofer preamplifier that incorporates a low pass filter circuit is the 4558 subwoofer preamplifier, which utilizes the JRC4558 integrated circuit (IC). In this article, we will dive into the specifications of the JRC4558 IC and discuss the importance and functionality of the low pass filter circuit in a subwoofer preamplifier.

Specifications of JRC4558 IC

The JRC4558 is a widely used dual operational amplifier IC that offers excellent performance and low noise characteristics. Here are the specifications of the JRC4558 IC:

  1. Input Offset Voltage: The JRC4558 IC has a maximum input offset voltage of 5mV, which ensures accurate signal amplification.
  2. Slew Rate: With a slew rate of 4V/µs, the JRC4558 IC enables rapid amplification of input signals.
  3. Bandwidth: The bandwidth of this IC extends up to 3MHz, making it suitable for audio applications.
  4. Supply Voltage: The JRC4558 IC operates within a recommended supply voltage range of ±4V to ±18V, ensuring compatibility with various power sources.
  5. Input Bias Current: It has a low input bias current of 250nA, minimizing distortion in signal amplification.

Low Pass Filter Circuit Diagram

This project can be designed using a few basic components. The circuit diagram of this project is shown below.

Low Pass Filter Circuit Subwoofer Preamplifier
Low Pass Filter Circuit Subwoofer Preamplifier

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Components List of Low Pass Filter Circuit

Following is the list of all components used in this project:

  • JRC4558 IC x 1
  • 1KΩ Resister x 3
  • 5KΩ Resister x 1
  • 10KΩ Resister x 3
  • 51KΩ Resister x 1
  • 22µF Capacitor x 2
  • 100nF Capacitor x 1
  • 0.63pF Capacitor x 1
  • 150nF Capacitor x 1

Importance of Low Pass Filter Circuit in a Subwoofer Preamplifier

A subwoofer is primarily designed to reproduce low-frequency sounds, such as deep bass. However, audio signals emitted by various music sources, including recordings and live performances, often contain both low and high-frequency components. To ensure that only the low-frequency signals are amplified and sent to the subwoofer, a low pass filter circuit is employed. Here’s what makes the filter circuit so essential in a subwoofer preamplifier:

  1. Frequency Control: The low pass filter circuit enables precise control over the cutoff frequency, which determines the range of frequencies allowed to pass through. This allows the user to tailor the subwoofer’s output to match the acoustic characteristics of the listening environment.
  2. Elimination of High-Frequency Noise: In audio systems, noise interference in the form of high-frequency signals can often degrade the overall audio quality. The low pass filter circuit ensures that these high-frequency noises are filtered out, resulting in a cleaner bass output.
  3. Protection of Subwoofer Driver: By limiting high-frequency signals, the circuit prevents these frequencies from reaching the subwoofer driver, reducing the chances of damaging it. This protection prolongs the lifespan and maintains the optimal performance of the subwoofer.
  4. Enhanced Clarity: The low pass filter circuit effectively removes high-frequency content, allowing the subwoofer to focus solely on reproducing the low-frequency components. This enhances the clarity and definition of bass notes, resulting in a more immersive audio experience.


In conclusion, the low pass filter circuit integrated within subwoofer preamplifiers plays a crucial role in ensuring the accurate reproduction of low-frequency sounds, while filtering out unwanted high-frequency signals. The JRC4558 IC, with its remarkable specifications, including low input offset voltage and input bias current, makes it an excellent choice for designing subwoofer preamplifiers using a low pass filter circuit. Whether you are an audio enthusiast or a professional sound engineer, understanding the functionalities and specifications of the JRC4558 IC and the importance of the filter circuit will undoubtedly help you achieve optimal audio performance and an immersive listening experience.

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Low Pass Filter Circuit Subwoofer Preamplifier Bass Booster
Low Pass Filter Circuit Subwoofer Preamplifier

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