Flanger Inverted Mode

A different type of maximum depth is obtained for $g=-1$ . In this case, the peaks and notches of the $g=1$ case trade places. In practice, the depth control $g$ is usually constrained to the interval $[0,1]$ , and a sign inversion for $g$ is controlled separately using a ``phase inversion'' switch.

In inverted mode, unless the delay $M$ is very large, the bass response will be weak, since the first notch is at dc. This case usually sounds high-pass filtered relative to the ``in-phase'' case ($g>0$ ).

As the notch spacing grows very large ($M$ shrinks), the amplitude response approaches that of a first-order difference $y(n) = x(n) - x(n-1)$ , which approximates a differentiator $y(t) = \frac{d}{dt}x(t)$ . An ideal differentiator eliminates dc and provides a progressive high-frequency boost rising 6 dB per octave (specifically, the amplitude response is $\left\vert H(\omega)\right\vert = \left\vert\omega\right\vert$ ).