It is not very well known, that the company that created the world's first dynamic processor was Telefunken in Germany. Their U3 compressors found practical application during the Olympic Games in Berlin in 1936.

The History

The fast pace of German industry in the 1930s helped to nurture a number of technology companies. At the beginning of the 40s, a new generation of compressors was introduced, the U13 by Telefunken was the first dynamics processor to use the diode bridge. After the war, work on the compressors of this type was taken on by Rhode und Schwarz, introducing the U23 model in 1954, widely used in broadcasting stations and the first recording studios.

In terms of design and sound it is similar to the American Fairchild 660 (after the war, the roles were reversed and the Americans became the technologically dominant designers). Although U23 sounded great, it did not meet the exacting standards of the IRT (Institut für Rundfunktechnik GmbH) and Telefunken was commissioned to carry out its successor. After three years of work, the Telefunken/AEG U73 appeared in early 60s. It was a tube compressor built in a configuration with variable transconductance (variable μ), offering theoretical compression ratio of 100:1 and the shortest reaction times in the history of tube processors thanks to the innovative feed-forward mode. U73 was produced by TAB, the owner of the license for the device, mainly for German-language broadcasting market. Quite a few U73s were also used in recording studios throughout Europe, where they found their place in every practically every vinyl record mastering room, especially the U73b version.

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