LA3161 Stereo Preamplifier Schematic Circuit Diagram

The LA3161 Stereo Preamplifier, denoted as “PREAMPlifier,” holds a pivotal role as the central control unit in a stereo or home theater system. It functions by directing low-level signals originating from audio and video sources towards the audio amplifiers, which then amplify the preamp’s output to levels suitable for driving the speakers. One fundamental feature of the preamp is its inclusion of volume control.

It’s worth noting that, in many instances, powered speakers still necessitate a distinct phono pre-amp. Nevertheless, the internal amplification and the presence of a built-in phono pre-amp offer the convenience of consolidating what would typically be two separate components – a receiver and an independent phono pre-amp.


Within the circuit, both of the integrated amplifier sections are actively utilized. Capacitors C8 and C9 serve as input coupling capacitors. Additionally, C3 and C6 take on the role of noise filter capacitors.

The lower cut-off frequency is contingent on the values of the C3 and C6 components. Meanwhile, the network, which incorporates elements R1, R2, and C1, plays a defining role in establishing the frequency characteristics of the left channel. Similarly, the network constituted by R3, R4, and C2 is instrumental in shaping the frequency characteristics of the right channel.

C4 and C5 are designated as output coupling capacitors. C7, positioned as the power supply filter capacitor, should be as closely connected as possible to the power input pin (pin 4) of the IC for optimal performance.

It’s important to note that this IC lacks short-circuit protection, and any short circuits between pins could result in damage. To mitigate the risk of interference, such as radio interference or engine-related disturbances, C10 and C11 are strategically included within the circuit.

Circuit diagram

LA3161 Stereo Preamplifier Schematic Circuit Diagram


  • Use 12V DC for powering the circuit.
  • The maximum supply voltage for LA3161 is 18V
  • The maximum allowable power dissipation is 200mW.

The LA3161 is a compact 2-channel pre-amplifier specifically designed for use in car stereo systems. Notably, it features an integrated voltage regulator, a critical component that significantly enhances ripple rejection. This IC is engineered to minimize the need for external components while maintaining an impressively low noise level. Additionally, it boasts a high input impedance of approximately 100K ohms and is conveniently packaged in an 8-pin SIL format.


  • Power supply – 9 ~ 12 VDC @ 20 mA
  • Output power – up to 200 mW
  • Input Resistance – 100 KΩ (Typ), Load Resistance – 10 KΩ (Typ)
  • Low noise, and good ripple rejection owing to the on-chip voltage regulator
  • Berg pins for connecting power supply, input, and output
  • Power-On LED indicator
  • Four mounting holes of 3.2 mm each
  • PCB dimensions 51 mm x 54 mm

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