ABBY is a powerful active A/B/Y switcher. It has a useful phase inverter toggle switch on Output B. When using 2 amps together that are out of phase a simple flick of the switch flips the phase of Output B 180°- problem solved. Output B is also fully transformer isolated to solve all ground loop issues.
This active and isolated A/B/Y pedal takes your input signal and splits it in 2 with a dedicated buffer for each channel. You can send the signals either one at a time (A/B mode) or both a the same time (Y mode). The phase on Output B can be inverted 180°, this means you can use 2 amps that are out of phase together. OUT B is transformer isolated to solve all ground loop issues that can arise from wet/dry rigs.
The circuit is active, so there's no loss in signal strength as it's not simply split in 2- each channel has its own buffer. This greatly reduces noise, crosstalk and problems with impedance or signal loading that can cause high end loss and overall tone loss.
This pedal can be the start of a wet/dry stereo pedalboard. It can also be useful to get a 2 channel setup on a single amp- on channel 1 (OUT A) you can put a distortion pedal or even a completely different pedalboard and on channel 2 (OUT B) have a different signal chain to switch between.