Small- Signal Audio Design

Chapter 10

Tone Controls and Equalizers

Facilities that alter the shape of the frequency response are called tone controls when they are incorporated in hi-fi systems, and equalization (or EQ) in mixing consoles.

Tone controls have suffered at the hands of fashion for some years now. It has been claimed that tone controls cause an audible deterioration even when set to the flat position. This is usually blamed on ‘phase-shift’. For a long time tone controls on a preamp damaged its chances of street (or rather sitting room) credibility, for no good reason. A tone control set to ‘flat’ – assuming it really is flat – cannot possibly contribute any extra phase-shift unless you have accidentally built in an all-pass filter, which would require truly ...