Emission Labs EML 274A / 274B Mesh RørPris er for 1 stk. rr! Guarantee The first owner can register the tube at the Emission Labs website, to participate in the 5 years guarantee program. DescriptionThis Data sheet. is about the 274A and 274B, which only difference is the tube base. These tubes are a full wave rectifiers of a special kind, and electrically equivalent to the original Western Electric historical tubes. Our tubes feature a series connected filament for both diodes together.