[randkyp]

If the equalization is done near the end of the audio output chain (ex: music player, defaults at 100% volume -> user sets master audio output volume to 50% -> EQ is applied) then a pre-amp is not strictly necessary if the EQ can take advantage of the extra headroom in the output channel. Otherwise, an adjustable pre-amp / gain setting would be nice, preferable with the option for it to automatically set itself to reduce by the maximum gain the EQ is applying to avoid clipping. But yeah, it should be optional; if the user wants stuff to clip, let it clip.