Under Me

This is a low pass filter kit that allows multiple rolloff frequencies below a range of 482 Hz to 3858 Hz to pass through.

Low pass filters are a specific type of rc (resistor-capacitor) filter that allows lower frequency signals through. Depending on the values of your resistor and capacitor, you can set different roll-off frequencies. This board allows you to have an 8 step range of roll-off frequencies depending on which transistors you choose to turn on or off.

Kit Parts:

  • 2x 17 pin headers
  • 8x 2n3904 NPN transistors
  • 16x 1k ohm resistors
  • 1x 0.33uF capacitor
Build Notes:
  • 2x 9 pin headers: These are purely for breadboard support.
  • 2x 8 pin headers: The 8 pin header labeled with 1-8 is for determining what your total resistance is across the RC filter you’re setting up with this board. Vin is where the signal goes in, and Vout is where the signal goes out. And of course the whole thing has to be connected to ground.
  • 8x 2n3904 NPN transistors: Remember to align the semi-cylinder with the silkscreen.
  • 16x 1k ohm resistors: These are vertically soldered and polarity doesn’t matter.
  • 1x 0.33uF capacitor: The polarity does not matter.

Example Set-up:

On the input jack is your unfiltered signal, and on the output jack, is your filtered signal depending on how many transistors you’ve triggered (yellow wires).

New to low pass filters? Not sure how to use them?