LA3161 Stereo Preamplifier Schematic Circuit Diagram

(PREAMPlifier) Meaning “before the amp,” the preamp is the primary control unit in a stereo or home theater system. It switches low-level signals from audio and video sources to the audio amplifiers, which boosts the preamp output sufficiently to drive the speakers. The preamp always includes volume control.
Most powered speakers still require a separate phono pre-amp. In any case, internal amplification and the built-in phono pre-amp eliminate the need for two separate components – a receiver and discrete phono pre-amp.


In the circuit, both of the built-in amplifier section is used. Capacitors C8 and C9 are input coupling capacitors. Capacitors C3 & C6 are noise filter capacitors. The lower cut-off frequency depends on the value of the C3 and C6 network comprising components R1, R2 & C1 defines the frequency characteristics of the left channel, and the network consisting of R3, R4 &C2 defines the frequency characteristics of the right channel. C4 and C5 are output coupling capacitors. C7 is the power supply filter capacitor and it must be connected as close as possible to the power input pin (pin 4) of the IC. This IC doesn’t have short circuit protection, and short between pins may cause damage. C10 and C11 are meant for preventing radio interference, interference from engines, etc.

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.

LA3161 is an integrated 2-channel pre-amplifier intended for car stereo applications. The LA3161 has a built-in voltage regulator which plays a great role in improving ripple rejection. The IC requires a minimum number of external parts and the noise level is very low. The IC has a high input impedance (around 100K) and is available in an 8-pin SIL package.


  • 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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