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Soft Magnetic Materials for Audio Transformers: History, Production, and Applications

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The history of soft magnetic materials is traced from 1000 B.C. to the present time. This includes a description of the work of Oersted and Faraday who invented the first transformer, and the gradual improvements in core material over the last 150 years. These cover soft iron, silicon iron, grain orientation, Hi-B steels, domain control by lasers, and spark ablation. Amorphous metallic glasses are also detailed. Finally the design and characteristics of a wide range of audio transformers and magnetic shields are discussed, in particular with regard to Mumetal, which with other nickel-iron alloys as been the author's lifetime occupation.

JAES Volume 35 Issue 10 pp. 760-777; October 1987
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Scott Dorsey
Scott Dorsey

Comment posted August 14, 2020 @ 18:32:36 UTC (Comment permalink)

This sort of paper would never be published in the journal today, sadly.  This is Dr. Sowter's basic overview of the history of audio transformers with some interesting notes about audio transformer design.  It's almost a stream of consciousness sort of piece.  It is by no means complete or authoritative, but it is a great overview for someone who wants basic background on audio transformer design and application.

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AES - Audio Engineering Society