Making the famous but frightening RDH work for the DIY tube audiophile
Why irreverence is essential in approaching the primary source
André Jute can’t get along without Langford-Smith’s RDH, so he refuses to be frightened off by the 1498 pages in which 10 authors and 23 collaborating engineers lay down The Law on Tubes
Radio Designer’s HandbookEdited by F. Langford-SmithNewnes, Oxford 1997 (a facsimile reprint of the final 1967 revision of the 4th edition, 1953). £35. Available from bookstores or direct from Customer Services Department, Heinemann Publishers Oxford, PO Box 382, Halley Court, Jordan Hill, Oxford Oxford OX2 8RU. Tel Int + 44 (0) 1865 314 301. Fax Int + 44 (0) 1865 314 029.
The Radiotron Designer’s Handbook, as it used to be called in Australia and the United States (the “Radio” title was introduced by the Wireless World/Iliffe British publication of the third edition of 1953), is an awesome 1498 pages of rather small print. But if you want to design audio and radio gear, you cannot do it without this book. There is no substitute. Let me emphasize that: There is no substitute for the RDH.
It’s predominance is hallowed by age. The first edition appeared more than two generations ago, in 1934. The third edition of 1940 is much thinner and less frightening than the present edition, but you will pay a lot more for it than the £35 (about $60) Newnes charges for their fine reprint, and shortly I shall show you how to cut the RDH down to size by the application of a little judicious iconoclasm.
The photolithographic reproduction of the text and illustrations is far superior to the RCA version of 1967 (which I also have). In fact, I assume the reproduction is by photographing from the Wireless World edition, rather than by resetting, simply because resetting would have been enormously expensive and certainly not within a £35 price or even three times that much. You may assume I know all about this. I earn part of my living as the chairman of a reprographics firm, and consult widely to publishers, so I am unfortunately familiar with typesetting and other origination costs.
The printing and binding by Gopsons in India is quite up to the elevated standard of Newnes’s parent companies Butterworth-Heinemann and Reed Elsevier. All sections are sewn and glued onto a heavily woven hemp backing, and then taped over for a belt and braces job. This book will not fall apart in a lifetime of use. That’s important, because for anyone seriously into valves (tubes), this is the one irreplaceable handbook, referred to many times each day. It is in hard covers and the plasticized outer seems sturdy enough though I imagine that in ten years or so it will be tacky and require rebinding. The cover is always the weakest link in a permanent reference book.
So what is in the RDH?
The one page publicity handout describes the contents as: “Valves, Generally Theory and Components, Audio and Radio Frequencies, Rectification, Regulation, Filtering and Hum, Complete Receivers, and Sundry Data.” That doesn’t even touch on the scope of this book. I would have said it is a risible summary, except that I cannot possibly in ten times the space provide a better summary.
The RDH starts from the basics of electricity and ends with the design of complete audio and radio gear, leaving out nothing.
Let’s just say that the RDH is the Complete Tube Book. If it isn’t in the RDH, it can’t be too important.
The only item I ever failed to find in the RDH which should be there is the SRPP or bootstrap voltage amp topology, which was published as early as 1946 in volume 18 of the MIT Radiation Laboratories Series--in a section dealing with filament balance! SRPP stages became important in tube audio band amps from about 1970. Related circuits of some importance, the mu follower and Alan Kimmel’s mu stage, are also not in the RDH, but they too came into use after the last revision of the final edition appeared in 1968. (Morgan Jones in his book Valve Amplifiers claims the mu follower is an old topology merely rediscovered in recent years but offers no proof.) Mentioning this single item -- all three topologies are variants of the same circuit -- in the context of the exhaustive treatment of the RDH makes me feel ridiculous, a nitpicker of the worst stripe. But a critic is supposed to criticize!
The RDH has an utterly exemplary index, and a very detailed list of contents to help you find your way. It is structurally equally exemplary, being most progressively organized by a very clear thinker. There is no waste and no duplication. The lists of thousands of references are exhaustive, though the truth is that in the seven or eight years that I have been living with the RDH I have never once had cause to refer to one of them, because the RDH itself always told me what I wanted to know.
The 920 drawing are clear and relevant.
The writing is clear and comprehensible in the style of engineers educated and cultured far beyond the standard prevailing today.
An approach to using the RDH
The publicity handout defines the “readership” as “Designers of radio and audio equipment, broadcast and audio engineers, audio enthusiasts, valve buffs, students of electronics, electronics hobbyists.” Once again the list doesn’t quite do the field justice. I can’t, for instance, imagine how a ham radio operator can get along without the RDH, unless he buys all his gear off the shelf, and has multiple other sources of information for all the incidental intelligence the RDH provides. Once again, making a full list will consume far too much space, and may anyway prove impossible.
Better just to say the RDH is all things tube to all men interested in tubes, and a lot of necessary things even to those merely interested in audio and radio applications of solid state electronics.
Every owner of the RDH will decide for himself what is most useful. I actually read through the entire 1498 pages once. But that was a procedure of desperate habit induced by reading too many poorly organized American computer books which one has to read through completely to discover the necessary information to which the contents and index do not guide you. The RDH does not suffer these shortcomings: it was organized and indexed by a clear thinker.
The RDH can be reduced to far less frightening proportions by intelligent use of the contents list. There are seven major parts, divided into 37 big chapters plus one “chapter” containing many appendices of Sundry Data
Let’s take the example of a serious audio hobbyist who wants to design an amp for himself to play LPs or CDs.
He can immediately forget the first part of 127 pages, which introduce the radio valve, its characteristics and its testing, as of interest only to collectors and specialist engineers. If he needs to know about, say, testing, he can always return there. He can also lose parts 4 and 6 on Radio Frequencies and Complete Receivers, well over 300 pages. If he ever wants to build a little tube radio to receive BBC4 in Ireland, as I recently did, he can return there.
Now he is left with three essential parts, still comprising a lot of chapters and pages. Some of these chapters can be left out altogether because they are the basic background to the parts of no interest to him. Those interested in audio but not radio need not read a chapter on Wave Motion and the Theory of Modulation.
Within the remaining parts, some chapters can be left out altogether because they are not relevant to the particular religion his interest imposes. Those who believe in zero negative feedback single-ended audio need not read the chapter on negative feedback, though if they use a cathode follower (which seems to have escaped their proscription) they will have to read at least part of it. Those who use only CD need not read a chapter on preamplifiers.
Within each long chapter, major sections can be skipped. Those interested in directly heated output triodes need not read sections on pentodes.
And so forth. Here is a list of chapters in which I have multiple bookmarks. Remember, I am interested in audio frequency music reproduction by tubes. Your own interests might be different. And we should note that my bookmarks fall much more heavily in the sections of these chapters in which I am interested (triodes rather than pentodes), instead of being equally divided.
4. Theory of Networks
This chapter is a complete introduction to electricity and circuit components and their resultants such as capacitance, inductance, impedance and admittance; it also takes in filters. Everything you ever wanted to know about circuits but were embarrassed to ask.
5. Transformers and Iron-cored Inductors
Essential reading before you speak to a winder about a custom transformer, and essential to an understanding of how tube amps work.
An introduction and graded treatment with worked examples of all the mathematical procedures used in designing an amplifier, including vector math for determining phase relationships. Also applicable to speakers.
10 Calculation of Inductance
12. Audio Frequency Voltage Amplifiers
13. Audio Frequency Power Amplifiers
These two chapters, spanning 122 pages, comprise the most complete guide to the design and operation of audio amplifiers in print anywhere. Others may be padded thicker, but this is the core from which they all derive. Why go for interpretations when you can mine the motherlode?
14. Fidelity and Distortion
19. Units for the Measurement of Gain and Noise
21. The Network between the Power Output Stage and the Loudspeaker
31. Filtering and Hum
These two chapters together contain all the essentials of power supply and decoupling.
33. Current and Voltage Regulators
38. Tables, Charts and Sundry Data
Some of the tables can save a lot of tedious iterative calculation.
All in all, this iconoclastic treatment has reduced the 1498 pages of the unabridged RDH to the 400 odd pages of information without which one cannot design a tube amp. Considering the small size of the the print, and the paddingless density of the information, that’s still an exceedingly hefty textbook, but ignoring any part of it can lead to expensive waste of components.
The beauty of this approach is that the contents list and the index will unfailingly lead you back to whatever you need in the other sections only when you need it.
Can I recommend the RDH?
Need you ask? There is nothing else like it. It is the one essential handbook, an outstanding bargain at the Newnes price, and the only possible complaint is that it is too much of a good thing.
Don’t be frightened off. Treat it resolutely as a mix and match menu of information from which you can select only what you need at any one time, and you can’t go wrong, especially since you can be supremely confident that anything you don’t understand is explained somewhere else and is instantly accessible through the contents and index.
© 1999 Andre Jute
André Jute was educated at universities in South Africa, Australia and the United States in psychology, economics and business management. He has worked in advertising, management consulting, and as a political and military advisor, and is now Chairman of the graphic and industrial design house Communication Jute. He is a distinguished novelist and writes a column on classical music read every week by 9.2m music lovers. Before taking up tube amp design, he designed and built complete automobiles.
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