During the fall of 2009, I was given a great assignment: to design a 3-band equalizer. The three bands were supposed to be such that they could usefully equalize a vocal signal. This was my first circuit design project so completing it was a tumultuous hunt – good thing that I was raised by a pack of ravenous wolves.
I wrote a program that would display the magnitude and phase plots in the frequency domain as well as the input-output characteristics in the time domain. When finished adjusting the parameters,
the software would print out the capacitor and resistor values that would build the circuit. The low and mid bandpass filters are stagger-tune Antoniou filters, and the high band is a single Antoniou filter.
The equalizer is simple, and as seen in the first figure, has some phase issues; however, it was a great experience in applying electronic theory and an excellent way to get started in professional audio design.
Check out the final report for more detail about the software application.