The A2.2 preamp uses a crossover circuit (the "XOM" design) to blend the best features of the AST (soundboard) and the UST (undersaddle) pickups. It adds soundhole-mounted blend and volume controls for easy, unobtrusive control over your onstage tone. I personally think these crossover mixes are some of B-Band's best pickup systems. When I've played with the A2.2, even when dialed completely toward the AST side of the blend, the tone is fattened up enough by the crossover that it sounds fantastic, noticeably better than the AST all by itself. The A2.2 has a mono output so you can plug straight into a board or DI—no need for an offboard blender. The entire package includes both the AST and UST (this is the only possible combo with the A2.2; you can't use B-Band's mic with this preamp).