DIY 4-Channel Audio Mixer: The LM3900 Project

A professional DIY audio project using the unique LM3900 IC. Simple, effective, and powerful.

Build Your Own 4-Channel Audio Mixer

Mix four separate audio sources into one output with minimal components. Perfect for instruments, mics, or line-level gear.

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Unlike standard op-amps, the LM3900 is a "Current-Differencing" (Norton) amplifier designed for single-supply operation.

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The inputs convert audio voltage into current. The IC sums these currents to create a clean final mix without crosstalk.

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No complex dual supplies needed. It runs smoothly on a single DC source ranging from 9V up to 24V

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We designed a professional, noise-minimized PCB ready for fabrication to ensure the cleanest signal path.

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Besides the LM3900 IC, you'll need standard passive components and four 10k potentiometers for individual volume control.

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Access the full project, including the Bill of Materials (BOM) and Gerber files for the PCB at elcircuits.com.

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A professional DIY audio project using the unique LM3900 IC. Simple, effective, and powerful.

Mix four separate audio sources into one output with minimal components. Perfect for instruments, mics, or line-level gear.

The Beauty of Simplicity

Unlike standard op-amps, the LM3900 is a "Current-Differencing" (Norton) amplifier designed for single-supply operation.

The Secret Component

The inputs convert audio voltage into current. The IC sums these currents to create a clean final mix without crosstalk.

Current Differencing Magic

No complex dual supplies needed. It runs smoothly on a single DC source ranging from 9V up to 24V

Versatile Power Options

We designed a professional, noise-minimized PCB ready for fabrication to ensure the cleanest signal path.

Compact PCB Layout

Besides the LM3900 IC, you'll need standard passive components and four 10k potentiometers for individual volume control.

Essential Components

Access the full project, including the Bill of Materials (BOM) and Gerber files for the PCB at elcircuits.com.

Get the Schematics & Files