GRAPHIC EQS & SIGNAL PROCESSING

EQUALIZATION (E.Q.) An equalizer is a device that can alter the spectral content of a signal. This can be done with any circuit that has an adjustable frequency response, the most familiar being the tone controls on a home stereo set. These tone controls typically affect the amplitude in two frequency regions, the treble and bass. This is sufficient for the minor changes the end user may wish to make in the program, but the recording engineer needs more flexibility and coverage of the entire audio spectrum. The complete studio will have complex e.q. systems that might include 30 or more regions of control. Many of these machines have sliders to adjust the amplitude of each band, and those sliders are laid out in such a way that their positions visually indicate the frequency response. This feature gives rise to the name GRAPHIC EQUALIZER.......... COMPRESSION It is also possible for the soft spots of a program to become too low in amplitude, especially in a noisy medium like AM radio. A program with a wide dynamic range may have to have that dynamic range reduced in order to fit a particular audio system. (Surprisingly, the current switch to digital audio is making this problem more common as stations try to fit the wide range of compact discs through the restricted dynamic window of FM transmitters.) A device which reduces the overall dynamic range of a signal is called a COMPRESSOR...............