 The original version was an all-tube combo amplifier with dual 12" speakers and two 6L6 tubes for a rated output of 25 watts.After the preceding looks of the early 1950s (TV front from 1950 to 51/2; wide panel '52–54), Leo Fender changed the cabinet design again, this time opting for no extra wood on the front of the amp, except for the narrow top and bottom panels that hold the baffle board to the cabinet.The early models of the larger "narrow-panel" tweeds are also remarkable for their refined electronics whose circuit design incorporated dual 5U4 rectifiers in the Twin and Bassman models, another improvement given Fender's quest for a louder, cleaner amplifier.