Cascaded Direct-Coupled Tube Systems Operated from Alternating Current
E.H. Loftin, S.Y. White · Proceedings of the IRE · 1930
An outline is given of the characteristics which are desirable in an audio amplifier or detector-amplifier. A description is given of some direct-coupled cascaded tube systems operating from a-c supply. Among the features which are discussed are: the reduction of current drain on the filter, the elimination of "motor-boating", stabilizing against drift of plate current, the elimination of hum and the provision of automatic change of grid bias with change of carrier input. The paper gives circuit constants and amplification-frequency characteristics for certain circuit arrangements.