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500 Series Equalizers:  While most 500 Series equalizers are parametric, you can also find graphic EQs that fit the chassis format. Parametric equalizers are the most widely used in situations where very fine control over the audio signal is desired. You’ll find mostly 3-band and 4-band parametric EQs in 500 Series formats. Many include low- and/or high-frequency shelving to handle cuts and boosts of signals above or below a specified frequency. In general, parametric EQs offer up to 12dB of boost and cut, which should handle just about any situation where EQ is desired.