Hi! I'm M.A. Mustafa. > Drawing on over 37 years of hands-on experience in electronics design and repair, I am proud to present this high-performance 5-band stereo audio equalizer. This is not just a basic circuit; it is a carefully crafted solution for audiophiles and makers seeking studio-grade sound clarity.
I have personally built and tested this zero-noise design. In fact, I’ve been using this exact equalizer board in my STK4191 audio power amplifier for over nine years without a single issue. You can see the performance and the build process in my 5-year-old YouTube video here: [ STK4191 Audio Power Amplifier Build With This Audio Equalizer].
This design features 5 rotary potentiometers, which are commonly recognized as a high-quality tone control circuit board or audio equalizer. However, its potential goes further- by simply replacing the rotary pots with slide potentiometers, you can transform this into a professional, full-fledged graphic equalizer. Whether you are looking for a deep bass boost, clear mid-range vocals, or crisp highs, this graphic equalizer schematic circuit diagram and construction guide covers all the professional techniques you need to build it yourself.
Why This High-Fidelity Stereo Design Stands Out
In the world of professional audio, precision in PCB and circuit design is everything. While many hobbyist designs rely on simple Zener diodes, this upgraded version integrates the NE5532 high-performance op-amp with dedicated KA7806 and KA7906 voltage regulators to ensure a rock-solid, noise-free dual power supply. For flexibility, you can also use the KA4558 op-amp as an excellent alternative.
What makes this circuit truly exceptional is its unique signal-to-noise ratio, delivering rich, crystal-clear audio across five frequency bands. This is no ordinary design; I have meticulously engineered this circuit by following the internal architecture of the legendary Sanyo LA3600 5-band graphic equalizer IC from Japan, ensuring world-class performance.
1. Comprehensive Stereo Schematic Circuit Diagram
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Figure 1: Professional 5-Band Stereo Audio Equalizer or Graphic Equalizer & Tone Control Schematic Diagram. This circuit delivers deep Bass Boost and high-fidelity audio as a premium alternative to the LA3600 IC, powered by NE5532 Op-Amps and 7806/7906 regulated supply. |
Understanding the 5-Band Frequency Control
To achieve precise audio tuning, this equalizer features five dual-gang rotary potentiometers (from RP1.1/RP1.2 to RP5.1/RP5.2). These allow you to adjust the specific frequency bands: 100Hz, 400Hz, 1KHz, 4KHz, and 10KHz. Here is a breakdown of what each frequency band does for your sound:
- 1. 100Hz (Deep Bass): This is the foundation of your sound. It controls the "thump" of the kick drum and the depth of the bass guitar. Increasing this adds warmth and power to your music.
- 2. 400Hz (Lower Mids): Often called the "Body" of the audio. This band controls the fullness of vocals and lower-range instruments. Proper tuning here prevents the sound from feeling thin or hollow.
- 3. 1KHz (Mid-Range/Vocals): This is the most sensitive range for human ears. It mainly controls the clarity and presence of the singer's voice. Increasing this brings the vocals to the front of the mix.
- 4. 4KHz (Presence & Detail): This band adds "bite" and definition to guitars, snares, and percussion. It makes the audio feel crisper and helps individual instruments stand out.
- 5. 10KHz (High-End/Shimmer): This controls the "Air" and brilliance of the audio. It adds a sparkling effect to cymbals and high-pitched sounds, giving your music that premium, studio-quality finish.
2. Professional PCB Layout & 3D Visualization
A great schematic deserves an equally perfect layout. This design is optimized for manufacturing with zero DRC (Design Rule Check) errors, ensuring a seamless production process for your business.
A. 3D Model Visualization
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Figure 2: 3D Visualization: A realistic preview of the final assembled PCB, showcasing precise component alignment and professional industrial aesthetics. |
This 3D rendering provides a realistic look at the final assembled board of the audio equalizer. It allows you to visualize component heights, terminal placements, and enclosure fitment before you even start the manufacturing process.
B. 2D Top Layer (Silk Screen & Component Placement)
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| Figure 2: Top Layer Layout: Clear silkscreen markings and component placement designed for error-free soldering and manufacturing efficiency. |
The top layer is designed with clarity in mind. With clean silkscreen markings and logical component spacing, soldering and assembly become effortless, reducing the chance of human error during production.
Perfect Star Grounding for Zero-Noise Audio Performance
To achieve a truly crystal-clear, hiss-free audio experience, this PCB layout has been meticulously designed with a Perfect Star Grounding system. If you are wondering why this is important, let’s explore what Star Grounding is and how it enhances your audio quality.
What is Star Grounding?
In simple terms, Star Grounding is a design technique where all ground connections from different sections of a circuit are brought back to a single, central point (the "Star" point). In standard daisy-chain grounding, noise from one component can travel through the ground line to another, causing "Hum" or interference. Star Grounding eliminates this by giving every section—input, output, and power—its own direct path to the main ground.
Why it is Essential for this Equalizer:
- Eliminates Ground Loops: It completely removes the annoying 50/60Hz "Hum" that often plagues DIY audio projects.
- Signal Integrity: By separating the signal ground from the power ground, the delicate audio frequencies remain pure and untouched by power supply ripples.
- Maximum Stability: It prevents unwanted oscillations, ensuring that your equalizer remains stable even at high volume or maximum bass boost.
C. 2D Bottom Layer With Star Grounding (Precision Routing)
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| Bottom Layer Routing: Optimized signal paths and trace widths engineered to minimize EMI and ensure pure, noise-free audio output. |
The routing on the bottom layer follows professional audio engineering standards. Optimized trace widths and strategic signal paths minimize crosstalk and electromagnetic interference (EMI), ensuring the purest audio output.
3. Complete Bill of Materials (BOM)
To achieve the best results, I recommend using high-quality metal film resistors and audio-grade capacitors. Below is the essential component list for this project:
| Resistor | Value | Watt and Advice |
|---|---|---|
| R1 To R10 | 4.7KΩ | 1/4 Watt |
| R11 To R20 | 1.2KΩ | 1/4 Watt |
| R21 To R30, R33 R34 | 68KΩ | 1/4 Watt |
| R31* To R32* | 3.3KΩ | 1/4 Watt |
| R35, R36, R39, R40 | 10KΩ | 1/4 Watt |
| R41, R42 | 1KΩ | 1/4 Watt |
| Capacitor | Value | Volt |
| C1, C2 | 68nF | |
| C3, C4 | 120nF | |
| C5, C6 | 18nF | |
| C7, C8 | 330nF | |
| C9, C10 | 6.8nF | |
| C11, C12 | 120nF | |
| C13, C14 | 1.8nF | |
| C15, C16 | 33nF | |
| C17, C18 | 560PF | |
| C19, C20 | 10nF | |
| C21, C22, C37, C38 | 3.3µF | |
| C23, C24 | 100nF | |
| C29, C30 | 100µF | 25V |
| C33, C34 | 470µF | 25V |
| C35, C36 | 1000PF | |
| Transistor | Value | Details |
| Q1 To Q10 | C1815 | NPN BJT |
| IC | Value | Details |
| U1 | KA7806 | +6V Regulator |
| U2 | KA7906 | -6V Regulator |
| U3A-U3B | NE5532 / 4558 | OP AMP |
Key Features of This Circuit:
Zero-Noise Performance: Optimized with Star Grounding and a regulated dual power supply to eliminate hum and hiss.
Studio-Grade Clarity: Precise 5-band frequency control (100Hz to 10KHz) for a rich and balanced audio experience.
High Component Density: Designed with 92 high-quality components, ensuring a professional discrete-component architecture.
LA3600 Equivalent: A robust and reliable alternative to the famous Sanyo LA3600 graphic equalizer IC.
Field-Tested Reliability: Proven design used in high-performance STK4191 amplifiers for over 9 years.
Zero-Noise Performance: Optimized with Star Grounding and a regulated dual power supply to eliminate hum and hiss.
Studio-Grade Clarity: Precise 5-band frequency control (100Hz to 10KHz) for a rich and balanced audio experience.
High Component Density: Designed with 92 high-quality components, ensuring a professional discrete-component architecture.
LA3600 Equivalent: A robust and reliable alternative to the famous Sanyo LA3600 graphic equalizer IC.
Field-Tested Reliability: Proven design used in high-performance STK4191 amplifiers for over 9 years.
Need a Custom PCB Design?
Whether you need a custom version of this equalizer or a completely new electronic design, I am here to help. With decades of professional experience, I deliver manufacturing-ready PCB layouts tailored to your specific needs.
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