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DIY Audio Frequency Filters

An audio frequency filter is an electronic circuit that works on electrical signals from microphones, amplifiers and other sound-related equipment. A filter removes a range of frequencies from the sound signal to reduce noise or to create sound effects: Tone controls, graphic equalizers and guitar "wah-wah" pedals are all audio frequency filters. The simplest filters consist of a resistor and capacitor, where one is in a series circuit with the signal and the other is in parallel. If the capacitor is in parallel, the circuit is a low-pass filter, progressively reducing frequencies past a known cut-off point.

Things You'll Need

Solderless breadboard
1-microfarad, 50-volt capacitor
10K-ohm, 1/4-watt resistor
4 12-inch pieces of 22-gauge wire
Labeling tape
Pen

Instructions

- 1
  Insert the capacitor's leads into adjacent columns of the breadboard. Holes in the breadboard columns are connected internally, but adjacent columns are electrically isolated from each other. To connect to a component already in a column, insert a wire or lead into another hole in that column.
- 2
  Set one of the resistor's leads so it shares a column with one of the capacitor's leads. Insert one end of the first and second wires so they connect to the other capacitor lead. Insert the other resistor lead into a free column on the board. Insert the end of a third wire so it connects to this resistor lead. Set the end of a fourth wire so it connects to the other resistor lead.
- 3
  Wrap a label around the first and third wires and write "Input" on the label. Wrap a label around the second and fourth wires and write "Output" on it. Connect the wires labeled "Input" to the output of an audio source such as a microphone, tape recorder or MP3 player. Connect the wires labeled "Output" to the input of an audio amplifier. The cut-off frequency of this filter is 100hz, so it passes lower frequencies than this and reduces higher ones.

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