Experimenting with parallel effects chains a snap, in mono or stereo. For example, you can plug whatever effect(s) you have connected to the send into a second amplifier or mixer/recorder channel. It can also be used just like a two-channel mixer itself by plugging a second source into the return jack. There is also a low-pass filter (capacitor to ground) on the clean signal that can be switched in for even more low end.
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