New Developments in Output-Transformerless Amplifiers
The subject of this paper is an audio power amplifier in which a number of principles have been combined in order to obtain very good performance at a reasonable price. The principles are not new themselves, but the combination has led to results which certainly may be called interesting. First a brief review will be given of the reasons that led us to the use of single-ended push-pull circuits and the development of a high impedance loudspeaker. The suitability of this system for a combination of positive and negative feedback will be discussed. Detailed circuits are shown and a method for calculation of the distortion figures will be indicated, first for a simplified circuit, and then for the amplifier as it has been built. The measuring results will be shown and discussed. Finally a demonstration will be given.
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