If a guitarist wants too use effects such as stomp boxes with their amp they’ll need to use the amps effects loop. The most important part off the effects loop is where it is placed in the amps signal. This is after the preamp stage and where the overdrive sounds are generated and before the power amp stage where the overall signal is amplified. Having said that certain effect pedals such as overdrive, wah wah, and compresson are best placed in the input stage of the amp. Modulation effects such as delay, chorus, flanger and phaser are best routed via the effect loop.