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.
In inverted mode, unless the delay
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
(
).
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
).