Capacitor in parallel in an audio circuit: Low pass filter.

Capacitor in parallel in an audio circuit: Low pass filter. A variable audio oscillator is hooked to a RC circuit. The circuit passes low frequencies and blocks high frequencies, as can be observed on the oscilloscope. Capacitance and resistance can be varied. A good set of starting values is 15 micro f capacitance, and 100 ohms resistance. Maximum signal is at 20 Hz; signal is attenuated by 50% at 1800 Hz (6 db down); and by 90% at 5400 Hz (20 db down). Closing or opening the key-switch allows one to check the frequency attenuation. Note: sweeping through frequencies will not produce an audible perceived decrease in amplitude due to our ear_s greater sensitivity to higher frequencies. CAPACITANCE