What does the Loop Level Switch do?
Some Marshall amplifiers are equipped with a Loop Level switch located on the rear panel (Fig. 3.1); normally right next to the Effects Loop jacks. This switch provides a +4dB or -10dB (db = decibel) compensation for the various effects that can be run through the loop. The general suggestion is that the -10db setting should be used for stomp box type effects. The +4dB setting should be used for rack/floor processors. However, as effect manufacturer specifications tend to vary greatly, we suggest trying both positions regardless of the effect. Feel free to experiment and decide which yields the strongest and cleanest tone.
