Based on the root word, equal, an equalizer is an audio device whose function is to equal out the tonal characteristics of a sound. At least that was the idea back in the days when they were first conceived as a tool used to get flat response in telephone lines and to make up for the deficiencies in audio equipment and acoustic spaces. Nowadays it could more aptly be named an “unequalizer” since they are more often used creatively to alter the relative balance of frequencies to produce desired tonal characteristics in sounds. An equalizer has the ability to boost and/or cut the energy (amplitude) in specified frequency ranges by employing one or more filter circuits. There are many different types of EQ’s in use today in many widely varying applications, but they fundamentally all do the same thing.