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Valve Amplifiers, Fourth Edition



Valve Amplifiers, Fourth Edition

Author: Morgan Jones

Publisher: Newnes

Genres:

Publish Date: August 13, 2012

ISBN-10: 0080966403

Pages: 700

File Type: PDF

Language: English

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Book Preface

Almost 40 years ago the author bought his first valve amplifier; it cost him d3, and represented many weeks’ pocket money. Whilst his pocket money has increased, so have his aspirations, and the DIY need was born. Although there were many sources of information on circuit design, the electronics works gave scant regard to audio design, whilst the Hi-Fi books barely scratched the surface of the theory. The author, therefore, spent much time in libraries trying to link this information together to form a basis for audio design. This book is the result of those years of effort and aims to present thermionic theory in an accessible form without getting too bogged down in maths. Primarily, it is a book for practical people armed with a calculator or computer, a power drill and a (temperature-controlled) soldering iron. The author started a B.Sc. in Acoustical Engineering, but left after a year to join BBC Engineering as a Technical Assistant, where he received excellent tuition in electronics and rose to the giddy heights of a Senior Engineer before being made redundant by BBC cuts. He has also served time in Higher Education, and although developing the UK’s first B.Sc. (Hons.) Media Technology course and watching students blossom into graduates with successful careers was immensely satisfying, education is achieved by class contact  not by committees and paper chases.

Early on, he became a member of the Audio Engineering Society, and has designed and constructed many valve pre-amplifiers and power amplifiers, loudspeakers, pick-up arms and a pair of electrostatic headphones.

It is now 18 years since work began on the 1st edition of Valve Amplifiers, yet much has changed in this obsolete technology since then. The relentless infestation of homes by computers has meant that test and measurement has become both cheaper and more easily integrated, either because it directly uses the processing power of a computer, or because it borrows from the technology needed to make them. Thus, the Fast Fourier Transform has become a tool for all to use, from industrial designer to keen amateur  enabling spectrum analysis via a d100 sound card that was the province of world class companies only 20 years ago. As a happy consequence, this edition benefits from detailed measurements limited primarily by the author’s time. Computer modelling is now freely available  exemplified by Duncan Munro’s PSUD2 linear power supply freeware.

The spread of Internet trading has made the market for valves truly global. Exotica such as Loctals, European ‘Special Quality’ valves, and final generation Soviet bloc valves are now all readily available worldwide to any Luddite with the patience to access the Internet  we no longer need to be constrained to conservative (but expensive) choices of traditional audio valves. Even better, many of the 1950s engineering books that you thought had gone forever are available from the second-hand book sellers on the Internet.

Paradoxically, although digital electronics has improved the supply of valves, other analogue components are dying. Capacitors are the worst affected by the lack of raw materials; polycarbonate disappeared in 2001, and silveredmica capacitors and polystyrene are both endangered species. Controls have succumbed to the ubiquitous digital encoder, so mechanical switch ranges
have contracted and potentiometers face a similar Darwinian fate. It is particularly galling to discover a use for Zeners just as major semiconductor manufacturers stop making them.

Despite, or perhaps because of, these problems, valves and vinyl have become design icons, both in television adverts and the bits in between. The relentless hype from manufacturers of audio servers that favour convenience over sound quality has forced manufacturers of CD players to justify their products on sound quality (and convenience, because although nobody mentions it, a CD player is unable to wipe your entire music library at the drop of an operating system). CD and vinyl are now the only reliable sources of quality audio  which is perhaps a step forward from the 1980s when it was FM radio and vinyl.


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