User`s manual

98
4.4.14: 20-Band Graphic Filter
The 20-band Graphic Filter is an easy-to-use linear-phase FIR digital filter that is used to
reshape the spectrum of the final output signal. Reshaping is accomplished with twenty
vertical scroll bars (also called "slider" controls) which adjust the attenuation of each
frequency band. These controls are very similar to the slider controls found on analog
graphic equalizers found on many consumer stereo systems, and thus should be very familiar
to even the novice user.
However, unlike analog graphic equalizers, this digital equalizer has some very powerful
additional capabilities. For example, the Normalize button allows the user to instantly move
all slider controls up until the top slider is at 0dB. The Zero All button instantly sets all the
sliders to 0dB, while the Maximize button instantly sets all the sliders to -40dB. The All
Down 1dB button instantly moves all sliders down in 1dB increments. The Link Frequency
Sliders feature allows all the sliders to move together in sync whenever one is moved. None of
these functions is available in an analog graphic equalizer! Notice also that the 20 sliders are
spread across the selected Bandwidth and that the frequency spacing is optimized for voice
processing.
Additionally, since a computer with a disk drive operates the equalizer, a Store and Recall
capability is available. This allows the user to store commonly-used slider configurations in
disk memories so that they can be instantly recalled later whenever they are needed, without
having to manually adjust the slider controls.
Description of controls/indicators is as follows:
Slider controls: The twenty vertical scroll bar "slider" controls are used to set the
frequency response of the equalizer. Each slider can set the gain of its
frequency band to any value between 0dB and -40 dB in 1dB steps.
Figure 4-59 20-Band Graphic Filter Control Window