Somewhat based on the legendary Fairchild 660 the EAR 660 has taken things a step further. The characteristics of the 'compression knee' around the attack and release parameters contribute to the unit's amazing performance. The onset of limiting is gentle enough to call attention to the fact that the unit is limiting, though it will react exceptionally quickly when called upon to do so. The audio circuit conforms to EAR's quest for low distortion and high headroom giving the sound a space and dimension found in few units ever built. If you're serious about the quality of your audio this is a "must have" tool.