A stereo preamplifier is a key part of audio systems.
It boosts weak audio signals from things like microphones or other audio devices so they can be amplified or processed better.
LA3161 is a two channel pre amplifier designed for car stereo systems, it is a low noise preamplifier integrated circuit providing great performance with very few extra parts needed.
It features a built in voltage regulator that helps reduce noise and improve sound quality.
This article will go over how a stereo preamplifier circuit works using the LA3161 IC including how to build with formulas and calculations for the circuit and a conclusion at the end.
Circuit Working:
Parts List:
| Component | Specification | Quantity |
|---|---|---|
| Resistors (All resistors are 1/4 watt unless specified) | 100k | 2 |
| 7.5k | 2 | |
| 100Ω R5 and R6 | 2 | |
| 150Ω | 1 | |
| Capacitors | Ceramic 1000pF | 2 |
| Ceramic 0.01µF 2 | 2 | |
| Electrolytic 47µF 25V | 3 | |
| Electrolytic 10µF 25V | 4 | |
| Semiconductors | IC LA3161 | 1 |
This circuit operates on a 12V power supply.
The IC LA3161 can handle a maximum supply voltage of 18V and can dissipate up to 200mW of power.
The left and right audio inputs are connected through capacitors C8 from pin 1 and C9 from pin 8 to block any DC signals.
There are also extra capacitors C10 and C11 that help get rid of high frequency noise.
The LA3161 integrated circuit boosts the weak input signals.
Feedback networks made of resistors R1 and R4 and capacitors C1 and C2 help manage the gain and frequency response of the amplifier.
Capacitors C4 and C5 are used to separate the amplified signals allowing only the AC signal to go to the output.
The outputs audio left out and audio right out can be used for more amplification or can be used directly.
Capacitors C6 and C7 help stabilize the power supply voltage and cut down on noise.
Formulas with Calculations:
The formulas for Stereo Preamplifier Circuit using IC LA3161 is mentioned below
Voltage Gain (AV):
The voltage gain of the LA3161 can be approximated using:
AV = R4 / R3
Substituting the resistor values:
AV = 100k / 7.5k = 13.33
This indicates the signal is amplified approximately 13 times.
Cutoff Frequency (fC):
The cutoff frequency for the feedback capacitor and resistor network is:
fC = 1 / (2π R C)
Substituting values for C1 and R1:
fC = 1 / (2π × 100,000 × 0.000000010) = 159.15 Hz
This determines the low frequency response of the circuit.
How to Build:
To build a Stereo Preamplifier Circuit using IC LA3161 following are the steps you need to follow the assembling:
- Gather all the components as mentioned in the above circuit diagram.
- Connect pin 1 of IC LA3161 to audio left input through capacitor C8, connect a capacitor C10 between capacitor C8 and audio left input and GND.
- Connect pin 2 of IC LA3161 resistors R2, R1 and capacitor C1 in series, connect from pin 2 capacitor C6 and resistor R6 and GND.
- Connect pin 3 of IC LA3161 to audio left output through capacitor C4
- Connect pin 4 of IC LA3161 to +12V positive supply through resistor R7, connect capacitor C7 from positive supply and GND.
- Connect pin 5 of IC LA3161 to GND.
- Connect pin 6 of IC LA3161 to audio right output through capacitor C5.
- Connect pin 7 of IC LA3161 to resistor R3, R4 and capacitor C2 in series, connect capacitor C3 and resistor R5 from pin 7 and GND.
- Connect pin 8 of IC LA3161 to audio right input through capacitor C9, connect capacitor C11 between capacitor C9 and audio right input and GND.
Conclusion:
The Stereo Preamplifier Circuit using IC LA3161 is a great and easy way to boost audio signals.
It has fewer parts and works really well making it perfect for different audio projects.
Users can change the component values to adjust the gain and frequency response to fit their needs.
This circuit is awesome for both hobbyists and professionals who want to improve their audio systems.