Here’s what Boss say
The BOSS PH-3 Phase Shifter pedal provides a wealth of vintage and modern phasing effects, including new “Rise” and “Fall” modes for unique, unidirectional phasing. Syncing these phasing effects is as simple as tapping the pedal to the desired tempo, while an optional expression pedal provides realtime control of the PH-3’s Rate, Filter and Tempo.
In addition to standard up and down cycles, the new PH-3 Infinite Phaser can produce entirely upward or downward moving sounds through its new Rise and Fall effects. There’s also 4-, 8-, 10-, and 12-stage phasers, plus a Step effect.
Syncing the PH-3’s phasing effects can be achieved by simply tapping the pedal to the tempo desired. Or, for maximum control, connect an optional expression pedal to control both rate and filter in real time as you play.