The LEHLE 1AT3 is a programmable True Bypass switcher that lets you switch backwards and forwards between up to three amplifiers, when you want, as often as you want.
In combination with jack socket C→B, output C can also be used alternatively as an effect loop for amp B, excluding all the effects you don't currently need from the signal path. A tuner can also be connected to output A, taking it, too, out of the signal chain. The gold-plated-contact relays feature active pop-and-click suppression, and switch not only the signal, but also the signal ground, making hum loops impossible when switching back and forth between outputs A, B and C.
This powerful switcher is lightly used and works great. It ships the next day!