A different type of maximum depth is obtained for . In this case, the peaks and notches of the case trade places. In practice, the depth control is usually constrained to the interval , and a sign inversion for is controlled separately using a ``phase inversion'' switch.
As the notch spacing grows very large ( shrinks), the amplitude response approaches that of a first-order difference , which approximates a differentiator . An ideal differentiator eliminates dc and provides a progressive high-frequency boost rising 6 dB per octave (specifically, the amplitude response is ).
Flanger Feedback Control
Flanger Depth Control