On the Theory of Power Amplification

1. In order to supply a maximum output wattage to an inductive loudspeaker by means of high-power tubes, regardless of the necessary amplitude of Eg, it is necessary to calculate the plate battery and grid-biasing potentials required to ensure distortionless reproduction. 2. From the inductive load on the plate circuit of the tube an elliptical shape of the working characteristic follows, referring to the egiip diagram. 3. If the working ellipse is enclosed by a rectangular quadrangle, the sides of which are parallel to abscissa and ordinate axes respectively, then the slope or angle ops of the diagonal of this quadrangle means the dynamic slope or mutual conductance of the tube for the given plate-circuit load, for 7vpz IV Eg 4. By means of ops and starting from the conditions of distortionless reproduction the position of the diagonal of the quadrangle and its useful part are determined and furthermore the following equations for the minimum necessary plate-battery potential as well as for the necessary grid-biasing potential are found: EB = K+ I3,( rp+ Rb) + IpV( wL) 2+ ( rp + Rbw) 2= Eg * Iu ECCEG-Ip3,\/( wL) 2+ ( rp + Rw) 2 5. It is shown what conditions result if several loudspeakers are connected in series or in parallel with each other or if several tubes connected in parallel are employed to supply the loudspeaker. 6.