What does a phaser actually do?
As mentioned, phaser effects are reliant on all-pass filters. All-pass filter is a type of filter that affects the phase of a signal without changing its amplitude. Unlike low-pass, high-pass, or band-pass filters, which alter the strength of certain frequencies, an all-pass filter allows all frequencies to pass through at equal volume but shifts their phase by different amounts.
A phaser effect is built using multiple all-pass filters in series. In isolation all-pass filters aren’t audible, but when the original dry signal is mixed in and the filter cutoff frequency of the filters are modulated by an LFO, the interaction between the original and phase-adjusted signals creates phasing’s sweeping, swirling effect.
Let’s look at Phasis’ interface to see the most common types of Phaser FX parameters.
