An inexpensive book on winding your own high end tube amplifier output and power transformers, reviewed by Andre Jute.
How to wind your own high end tube amp transformers
a review by André Jute of
Coil design and construction manual by B B Babani
Bernard Babani (Publishers) Ltd, 1960, reprinted 1995
ISBN 0-85934-050-3
Stg pounds 3.95 (that's about 6 American dollars)
Bernard Babani Ltd is a British house which publishes books in electronics, computers and so on. Production of their paperbacks is cheap and cheerful but the Babani list is famous for its high standard of information.
Babani himself is an electrical engineer. This week I found at Easons (the Irish version of W H Smith or Barnes & Noble) a copy of a book by Babani himself, written in 1960 and reprinted umpteen times since, the last time in 1995.
B B Babani's Coil Design and Construction Manual contains clear and concise plain English instructions for designing and building RF coils, audio frequency PP and SE interstages and outputs, power supplies, filter and power chokes, etc. Babani has that crystal style of British engineers of a bygone pre-jargon generation which considered proselytization a holy crusade. (The thriller writer Len Deighton once said that he tries for the sentence his reader might think he wrote himself. Only another writer knows how much work that sort of simplicity consumes. But there was a time within living memory when almost all educated men were taught to write like that.)
The basic assumption is that the reader knows Ohm's Law, understands that L, C and R are different, and can handle simple algebraic transformation. Babani takes it from there, explaining what impedances and reactances are and how to calculate them and their effects in the frequency band of interest. All the necessary formulae are clearly explained.
The short chapters follow a logical development from ignorance via design to winding tips. There are lookup tables to simplify design around various proportions of windows in laminations, with notes about which shapes and types of winding work best for different purposes. There are also the usual wire tables.
Within its limits, this is a complete book. The amateur can start at the beginning and work his way through, and if he takes care to observe all Babani's warnings and tips, wind a good set of transformers for his amplifier. However, because the book is aimed at DIYers, it is entirely focussed on EI and UT laminations; there is nothing about toroids, C-cores and other advanced types that are difficult for amateurs to source materials for or, in a practical sense, to wind successfully.
Frankly, I have my doubts about whether for a single transformer one could source the materials and give the hours to the winding even for several multiples of what Lundahl or Sowter charge for a complete transformer, but of course that does not take into account the satisfaction of doing the job right yourself, or having experimentation under one's own control. And, of course, if one is building a Sakuma-style amp with transformers all over the place, materials sourcing becomes much more economically feasible, and savings may accrue. My own T49, which was nowhere near as extreme as Sakuma at his most iron-happy, had 12 transformers, and was upgraded in the T53 to 14 pieces of iron...
But even if one has no intention of winding a single transformer, it is necessary even for the serious tube audiophile, and essential for the amplifier designer, to know how transformers are made. There is no quicker introduction than B B Babani's Coil Design and Construction Manual. Babani nicely complements Menno van der Veen's Transformers and Tubes in Power Amplifiers (also reviewed on this page), which takes an application rather than a construction approach to transformers, and which thoroughly but accessibly explains the theory missing from Babani.
Copyright © Andre Jute 1999
THE VOLTAGES IN THIS AMP WILL KILL YOU
GET EXPERIENCED SUPERVISION IF IT IS YOUR FIRST TUBE AMP
All text and illustration is Copyright © Andre Jute
and may not be reproduced except by prior permission