An ultrasonic tab welder, useful for welding metal ribbon to metal sheet, has an ultrasonic stack having a horn configured to include a pair of ends between which are one or more upstanding welding stud surfaces and held by a bracket assembly. The bracket assembly includes a horn holder terminating at either end with U-shaped legs holding either end of the horn and an upper U-shaped legs having a generally horizontal piece carrying a strain gauge. A T-shaped assembly mated with the horn holder U-shaped legs that are carried by a U-shaped holder by a pair of downward holder legs. A pair of bearing assemblies are captured between the downward holder legs, the upper holder U-shaped legs, and the horn holder up U-shaped legs. The horn upstanding welding stud surfaces conformingly mate with the metal ribbon as it is welded to the metal sheet.