It's more than an EQ, it has some psychoacoustic processing and tricks up its sleeve. It's similar to BBE Mach3Bass, but even punchier, faster, and more natural sounding (and without making a loudness curve with recessed midrange, or affecting the treble). You have to hear it to believe it - personally I couldn't manage to tweak such a bass boost with the use of a regular EQ. It even makes the Koss KSC75 (!) into slightly bass-heavy yet still very clear cans.
Additionally, it's also amping the signal a bit (about as much as a FiiO E5, I'd say) - and it still doesn't distort the bass at all, not even at highest settings, playing some nasty Dubstep tunes with really low sub-bass.