Williamson amplifier
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A Williamson amplifier refers to a type of valve amplifier whose circuit design is similar to that originally published by D.T.N. Williamson.
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[edit] Explanation
Starting in 1947, the British magazine Wireless World published a series of articles by D T N Williamson, under the title "Design for a High-quality Amplifier." The design, later referred to as the "Williamson Amplifier" was, perhaps, one of the first examples of a high fidelity audio amplifier (although the LEAK "Point One" Type 15 amplifier of 1945 pre-dates it). The articles were detailed, which inspired many builders to construct copies, both for their own use, as well as for sale.
[edit] Description
The Williamson amplifier was of the 'push-pull' topology and used negative feedback, coupled with a special design of output transformer, to produce lower levels of distortion than previous designs.
The basic amplifier was designed to use GEC L63 triodes as phase inverters, and drivers. Later in August 1949, Williamson recommended 6SN7s for these positions. The output stages were triode connected KT66 pentodes, although a 6L6 was also recommended as long as its slightly lower output was taken into account.
The Williamson design demonstrates the maturity that tube amplification reached in the late 1940's. Other than the British Mullard 5-10 circuit and David Hafler's Dynaco ST-70, there was little improvement in the fundamentals.
[edit] References
D.T.N. Willamson, The Williamson Amplifier - A collection of articles reprinted from Wireless world, (Reprint 1994)
