We need an Audio mixer to amplify different audio inputs with a single amplifier. It is a quadruple Norton operational amplifier with a 14 pins dual inline package, Audio mixer circuit using IC LM3900 is simple and easy to create. The LM3900 provides a broad range of power supply voltages (4.5v to 32v).
The LM3900 is compliant with internal frequency, which allows us to mix and amplify four different audio inputs. The variable resistor VR1 – VR4 can vary from single input gain to audio. The circuit has only a minimum gain with a mixed audio output signal, and you can improve the audio output with an external amplifier.
Hardware Components
The following components are required to make Audio Mixer Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | IC | LM3900 | 4 |
| 2. | Variable Resistor | 1K Ohms | 4 |
| 3. | Resistor | 1M, 330 Ohms, 470 Ohms | 4, 5, 1 |
| 4. | Capacitors | 0.1uF | 5 |
LM3900 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of LM3900
Audio Mixer Circuit
Working Explanation
We need an amplifier stage to build an Audio mixer circuit, and the LM3900 IC is used as the amplifier stage here. Each audio input is controlled with Variable Resistors (VR1 through VR4) to control individual audio channels easily. All internal amplifiers are used to amplify audio input signals.
Inverting the Amplifier input is provided by audio signals and non-inverting pins. 1M Resistor is used for all stages of feedback setups. Finally, with an external power amplifier, the output signals are combined.
Four LM3900 internal amplifiers work with high gain compensation independently. It only takes one source of power, and even a split supply can be operated. The bandwidth is wide, and the output voltage swing is large.
A regulated DC power supply and an audio signal that can be directly delivered as input or provided after pre-amplification is required for that audio mixer. Supply common ground (GND) for all non-inverting inputs. We should use an adjustable sliding potentiometer to make the circuit more professional instead of variable resistors.
Application and Uses
In audio electronics, Audio Mixer is a virtual device. Two or more audio signals are mixed into a single (mono) or two outputs (Stereo). The audio mixer uses audio mixing, which combines several sounds to create single or multiple sounds.
