Performance of Output Pentodes

The comparison of power output, distortion, power sensitivity, and a-c/d-c power economy of a group of experimental pentodes is made with corresponding triodes. The apparatus and method of measuring are described. The pentodes' a-c/d-c economy and power sensitivity is considerably higher than that of the corresponding triodes. The harmonic distortion is found to be generally worse with the pentodes. The variation in power output with changes in load resistance, arbitrarily called "output distortion," is shown to be about the same for both classes of tubes. The need of a large capacity shunting the bias resistor in a self-biased pentode amplifier is shown. Its effect on power output and power sensitivity is discussed. In the conclusion, five types of distortion occurring in triode and pentode operation are compared. The principal use for the pentode appears to be with battery and 110-volt d-c types of receivers.