Flanger Feedback Control

Many modern commercial flangers have a control knob labeled ``feedback'' or ``regen.'' This control sets the level of feedback from the output to the input of the delay line, thereby creating a feedback comb filter in addition to the feedforward comb filter, in the same manner as in the creation of a Schroeder allpass filter in §1.8.1 (see Fig. 1.24).

More generally, outputs of any subset of the allpass sections can be fed back to the input (in small amounts) to produce different sounding effects [228].