Chorus, Phaser & Flanger

Psychedelic effects are reached not only by popping acid or shrooms. Modulated phase or time shift effects like phasers, flangers and chorus will give you an adequate acoustic association, especially with high feedback. Basically all three effects are delay based effects but with different delay times and feedback settings. Phasers can have a lot of stages giving a deep effects, delays can be analog or digital, with the latter ones being able to simulate old tape delays as well.