Effects loop

A pair of sockets on an amplifier that break the signal path after the preamp and before the power section, so external effects can be inserted there.

The loop matters because of where distortion happens: pedals in front of the amp are themselves clipped by the preamp when it is driven, while pedals in the loop hear an already-distorted signal and can add delay, reverb or modulation without being mangled. A serial loop replaces the signal path entirely; a parallel loop mixes the processed signal back against the dry one, which some players prefer for time effects. Loops may be designed for line level, instrument level or switchable between the two, which affects what sits happily in them.

Example: a delay in front of a heavily driven amp turns into a blurry wash, while the same delay in the effects loop stays clean and audible.

Effects loop

See also