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Show Parallel Tubes Reduce Impedance; Aid Output In various set building experiments going on there appears to be an inclination in-clination toward the use of parallel tubes, that is, two tubes with their grids connected together to the input and their plates connected together to the output circuit. In studying this type of tube connection con-nection it must be borne in mind that the push-pull combination is not a parallel tube arrangement. It is more of a relay system. One tube takes up the signal when the other lets go. In connecting two grids together tooth grids are at the same voltage at 'iii' 2 M 1 1 System That Reduces Impedance and Improves the Output. the same time. Both plates, being connected con-nected together, are at the same voltage volt-age at the same instant. But an essential es-sential in smooth action is that both tubes must be alike, . which seldom happens. It is the same situation with a team of horses. Unless they are matched there will be a difference the work they do. Aside from these, considerations, putting the input circuits in parallel uts the Input impedance to one-half of its value.. Likewise, plate circuits In parallel cuts the output impedance to half value. In the output circuit, therefore, to match the tube imped-ance, imped-ance, the transformer or choke or resistance re-sistance would naturally have one- the Impedance it had when match-a match-a single tube. In other words, smaller chokes and smaller primary Inductances will give better results j1'3" the high values, assuming the Wter to be correct for a single tube, ''"t another way, the cheaper types J"1'0'1 do not give such desirable erects er-ects on a single tube should be bet-er bet-er n the parallel tube. |