Low-Level Audio Pre-amp

low level stereo audio pe-ampWith a 9V supply and low level input the output can run up to 4.2V Pk-Pk before distortion appears.  Frequency response is flat from about 100Hz to 12KHz.  Gain is set such that 20mV input is 1V output.  Trimmers options allow attenuation of the input and output.  It’s a text-book non-inverting op-amp circuit using a dual low-voltage rail-rail op-amp.

The LLP_1A1 version has -ve on the center pin of the DC power jack.  The result of working off the brief and partly illegible data sheet before having connectors in-hand.  There’s an option for a 2-pin power connector.  Probably more reliable long term than the DC jack anyway.

The picture show a stereo to mono version, but fully populated provides 2-channel stereo.

Product link here.


  • input with trimmer level adjustment
  • input without level adjustment
  • output with level adjustment  (bypass for no adjustment option at assembly at production)
  • 3.5mm stereo connectors
  • jumper for mono – connects 2 channels at input
  • mic input – 2.54mm pin header
  • 8-24V DC single rail power supply
  • 40x50mm board size

Application example:

  • pre-amp between a PC and typical amplified speakers allowing volume settings below 100% for a better output volume.