From the Manual:
4.15.3. Phaser
A phaser modifies the phase of the signal around some frequency, then adds it back to the
original signal.
Feedback
The output of the phaser can be fed back to its input, thus creating a resonant sweep. Both
positive and negative feedback is possible, at center position there is no feedback.
Dry/Wet
Mixes the dry and processed signal. Since the phasing effect is achieved by mixing the original
and processed signal, the mix ratio should be typically around 50%. Lower values can be useful
to make the effect more subtle, however, and higher values can be useful with strong feedback.
At no setting do I get "totally distorted".