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This paper discusses an amplifier circuit with high input impedance which permits push-pull operation from an unbalanced source. A voltage, proportional to the total circulating current of the push-pull system, is obtained from a transformer connected in the cathode circuits of the output valves. Over-all performance similar to usual push-pull operation may be obtained. The possibility of a single- or two-mode oscillator is also discussed. Because of the simplicity, and general application of this circuit, some of the more useful formulas are developed in detail.