Month: November 2008

You might be familiar with passive crossover network installed inside your speaker box, consist of inductors and capacitors. The problem with passive crossover network is that they dissipate the audio power, so it’s not environmentally friendly, contributing a little disaster of global warming.  Moreover, the capacitor and the inductor in the passive crossover network contribute the distortion of the signal […]

Notch filter is known as band-cut filter or band-reject filter. The fuction of this filter is to remove some frequency portion of a signal. The schematic diagram of this filter circuit, a second order notch filter is depicted in the figure below. The formula is actually complicated, but by taking the R3=R4 and C1=C2, the filter’s frequency response  formula become […]

The function of this circuit is similar with the hum filter in our previous circuit, but it use transistors instead of op-amps. It uses BC109 transistors, but any low noise high gain type will be suitable. This hum filter is adjustable via trimmer pots to fine tune it’s notch depth.   The figure below shows the schematic diagram of the […]