The BEHRINGER ULTRATWIN GX212 is equipped with a special circuit that gives you enormous flexibility using the overdrive channel. Owing to the rich upper harmonics spectrum of distorted sounds, the morphing filter circuit has quite a drastic effect on the overall sound. It does this by using an adjustable filter that manipulates the natural distortion harmonics in the signal that is being processed by the overdrive channel on the amp. This manipulation of distortion harmonics allows the user to create new sound nuances that would be impossible to create with a traditional passive EQ, giving the user a wide range of tonal possibilities to help tailor and create a unique sound.