Listen to the pop, sizzle, and hum. Look at the bars and wavy lines. These and other characteristics of electromagnetic interference (EMI) are very familiar. RF energy is radiated from a culprit ...
This subwoofer active filter circuit is a 24 dB octave filter with a Bessel character and cutoff frequency of 200 Hz. So, if you are interested in experimenting with audio circuits in subwoofer range, ...