The REX II’s advanced design eliminates the constant need to set and readjust the proper bias of the output tubes. An intelligent automatic bias circuit adjusts for changing line voltage and aging tubes. For convenience, LED indicators show the status of each individual output tube. BAT further extends the plug-and-play nature with a novel “fuse-less” protection circuit, which eliminates the power-supply rail fuses to provide both a more refined sonic performance and user-friendly experience. All you have to do in the event of an output tube being over-stressed is to flip the power switch. No tubes to bias.  No tube fuses to replace. It doesn’t get any easier!