Subwoofer preamplifier circuit SMD version with ne5532. An audio preamplifier for subwoofers with adjustable bass filter is an essential circuit for sound systems that require precise control of low frequencies, such as active subwoofers. Below, I explain the operation and characteristics of the circuit based on the NE5532, according to the provided diagram. It includes a diagram and printed circuit board (PCB) for free download. The PCB was designed in a star-shaped ground layout to avoid noise.

General Description of the Circuit
This circuit is designed to amplify audio signals and filter specific frequencies, allowing only bass (low frequencies) to pass through. It includes:

• Pre-amplification: amplifies the input signal to suitable levels.
• Adjustable filter: allows adjusting the cutoff frequency to customize the bass response.
• Volume control: adjusts the intensity of the output signal.
• Symmetrical power supply: provides +12V and -12V to power the components.

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Schematic Subwoofer preamplifier circuit SMD NE5532

Main Components

1. Power Supply
   1. Regulators 7812 (+12V) and 7912 (-12V) ensure stable voltages.
   2. Electrolytic capacitors (C1 to C10) and a bridge rectifier (DB107S) filter and stabilize the voltage.
   3. LEDs indicate the power status.
2. Operational Amplifier NE5532
   The NE5532, known for its low distortion and high quality, is used in various configurations:
   1. IC3A: Non-inverting amplifier with a fixed gain of 11.
   2. IC3B: Sallen-Key high-pass filter with a cutoff frequency at 20 Hz (eliminates unwanted noise below this range).
   3. IC4A and IC4B: Sallen-Key low-pass filters with adjustable frequencies between 66 Hz and 191 Hz.
3. Adjustments
   1. Potentiometer P1 (50k): Adjusts the cutoff frequency of the low-pass filter.
   2. Potentiometer P2 (50k): Controls the output signal volume.
4. Connections
   1. CN1: Audio input.
   2. CN2: Subwoofer output.
   3. CN3: Power supply input.

Circuit Operation

1. The audio signal enters through connector CN1.
2. The initial stage (IC3A) amplifies the signal with a fixed gain.
3. The high-pass filter (IC3B) removes very low frequencies (<20 Hz).
4. The signal passes through two consecutive stages of adjustable low-pass filters (IC4A and IC4B), which define the exact bass range reproduced by the subwoofer.
5. Potentiometer P1 allows adjustment of the low-pass filter cutoff frequency, while potentiometer P2 controls the output volume level.

Applications

• This circuit is ideal for:
  • Active subwoofers in residential or automotive systems.
  • 2.1 speaker systems or home theater setups.
  • DIY projects requiring precise bass control.

Assembly and Considerations

1. Use a transformer with a symmetrical output (+12V/0/-12V) to power the circuit.
2. To avoid noise, connect the potentiometers to the panel using shielded wires.
3. If you wish to change the frequency ranges, adjust the capacitor values in the Sallen-Key filters using specific calculators.

This project provides an efficient and customizable solution to enhance bass sound quality in audio systems, leveraging the versatile NE5532 operational amplifier.

Combine this board as the 2.1 amplifier with TDA7265.

BOM Subwoofer preamplifier circuit SMD NE5532

Last update: 01/25/2025 21:31

Download the files, links, and notes

Download the PCB in Gerber + BOM + Centroid File + PDF + PNG

Mirror

• Buy subwoofer filter
• PDF Datasheet IC NE5532 — Texas Instruments
• DF Datasheet IC NJM5532 JRC5532
• DF Datasheet IC LM7812
  DDF Datasheet IC LM7912
• DF Datasheet Bridge rectifier DB107S