As j-b if you want a equalizer setting which is applied to all audio/video files then change the values in the Preferences. To do this go to:
Settings >> Preferences... >> Audio >> Filters
And tick the "Equalizer with 10 bands" tickbox.
Then go to the "Equalizer" section within the "Filters" tree. From there an Equalizer preset can be selected. If you want your own custom preset then tick the "Advanced options" tickbox and enter the gain value in dB for each frequency range, separated by spaces. The easiest way to do this would be to make a note of the dB value for each slider when using the Extended GUI, and then enter them in the "Band gain" text box in the preferences. For example:
Would be 20dB for 60Hz, 15dB for 170kz etc.
Then press "Save" and next time audio is played the equalizer should be applied.
Cheers, Arite.