If your rig has been expanded by a second amplifier or you find yourself with two guitars that you want to jack into one amplifier, then the only practical solution lies in a splitter or router.
Line Splitters & Routers
A signal splitter pedal literally splits a single audio signal, like the signal of a guitar or bass into two identical signals that can be sent out to two different amplifiers or other external gear. So, if you're hooked up to two different amplifiers, you can then easily switch between two completely different sounds or use both amps at the same time to create super-rich and enveloping sound. A signal router is basically a more advanced version of a splitter and will usually supply a lot more inputs and outputs to support more flexible and complex switching. With a router, you can flip between specific instrument combos, effect combos and amplifier combos at the push of a button.
FX Loops: Deeper Effect Chain Control
The sound and function of any effect pedal can depend on the position it takes in your effects chain. Using an FX loop, guitarists and bassists can gain more control over the chain order. You can get pedals that function as a standalone effects loop, or you can get extensive signal splitters that also offer an FX loop function. For example, by slotting a splitter with an FX-loop switch into their effect chain, ambient guitarists are able to flip the order of their delays and reverbs at will.
