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The Self Compensated Output Power Transformer (SC-OPT), Theory and Properties

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Conventional OPT (CO-OPT), when used for Single-Ended tube amplifiers, have a great inconvenient due to the anode quiescent current which reduces the core magnetic flux capability, for the AC magnetic flux, before the core saturation. Usual solutions applied to solve this problem are based on air gapped magnetic cores, with large core cross section. Resulting performances are generally satisfying but lead to large, heavy and expensive OPT. This paper introduces a new concept of OPT: the Self Compensated OPT (SC-OPT). Its aim is to remove the above inconvenient. The magnetic flux, due to the anode quiescent current, is self compensated, offering to the AC magnetic flux, the whole core magnetic flux capability. As a result,for Single ended layouts,the limitations in size and power of the traditional airgapped transformers are overcomed and the SC-OPTs can be built for much higher power outputs, without becoming too bulky. The SC-OPT can deal with very large quiescent currents ( 2 Amps and above ), making it suitable not only for Hi-power triodes, but also solid state devices, such as mosfets. The same principle also applies to interstage transformers as well as filtering and plate chokes. Experiences have also revealed an improved clarity in the sound.

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