Equalization Technique    

Boosting or cutting frequencies results in a corresponding boosting or cutting of overall signal level.  In extreme cases boosting can result in clipping distortion and cutting can result in the noise floor of the equipment becoming audible. 
Changes made to the frequency characteristics of a signal. In phonograph and magnetic tape systems this refers to changes made to the signal before recording to compensate for the non-linearity of the medium.  Complimentary changes are made during playback to return the signal to its original spectrum.  In a simple way, one might accomodate the poor high frequency response of a cheap cassette tape recorder by boosting high frequencies on recording and attenuating them on playback.  This helps overcome the poor frequency response of the slow tape speed a little.
Care should be taken to not over-apply equalization at the recording stage, particularly frequency cuts. Once the energy in a frequency band has been attenuated it is very difficult to restore it using corresponding boosts later.  Similarly, if a program has had extreme frequency boosting at the recording stage and needs to be compensated for by a corresponding cut the resulting signal may lack sufficient level and become noisy.  This is particularly problematic with low frequncy boosts where the majority of signal energy occurs. 
If boosting a particular frequency range of the signal results in distortion, try cutting the complementary range instead. For instance, if you want to bring out the high frequencies but find distortion occurs when boosting them try cutting the low frequencies instead.