What is an effects loop?
Effects loops give you the opportunity to plug effects between the preamp and the power amp. This is best for modulation (phaser, flanger, chorus, pitsh shifting) and delay effects because it allows them to effect the distorted signal as opposed to the preamp distorting them. It also runs a line-level signal, instead of instrument, which works better with most rack mount effects. (Distortions and boosters, etc, usually work better going straight into the guiatr input where they can affect the preamp gain) Most have output jacks that run to the effects and input that run back to the amp. Regular guitar cable is good to use for these jacks. A few have one stereo jack that has both input and output and require a stereo-plugged “Y” guitar cable with one cable running as the input, one as the output. Serial effects loops rune directly between the preamp and power amp, parallel ones allow you to mix the “wet” loop signal with the “dry” preamp signal. You may also run the preamp signal out of