A-Y switching works two ways. It lets you switch a common source signal (guitar, bass or keyboard) between two amplifiers or amp channels. Or conversely, it lets you switch two source signals (ie, two different guitars) into the same amplifier. A good quality A-Y switcher will also provide LEDs or other indicators to show whether A, B or Y routing is in effect. The Y routing combines both the A and B outputs in parallel so that two amplifiers can be driven at once. The CoolSWITCH provides full...