effects loop

An effects loop, or fx loop, is a pair of Send and Return jacks on an amp placed between the preamp and power amp sections, adopted from mixing console inserts in the 1970s¹. It lets pedals sit after the gain stages, where effects can be sculpted and refined rather than hitting the amp's front end². The loop circuit can be built with tubes, opamps, or a combination of both¹. Effects such as chorus may sound good in front of the amp but even better in an effects loop, blending well with high-gain distortion³. Effects loops also appear on pedals and multi-effects units, such as a built-in loop that drops effects between drive and wet channels⁴.