Its most apparent on certain bass notes- the processor inserts a higher pitched discordant tone that sounds clacky like its a square wave. When I play pure sine test tones, its much louder with some frequencies than others, and much louder when out of phase tones are played. With a sweep, I hear the higher tone sweeping the opposite direction as the real tone, and it comes in and out during the sweep. The main R and L speakers do not play the sound- only the center and the rear surrounds. Not sure about the sub since the distortion tones are too high of frequency to make it past the sub's crossover. I think a bit is being dropped somewhere which is why it aliases during a sine wave sweep, and is absent at some frequencies (where the dropped bit is correct).