Andre Jute looks into the difficulty of getting information on winding output transformers for tube audio and recommends books suitable for DIYers.
Understanding high end transformers -- and perhaps even rolling your own
a note by Andre Jute
to relate several books reviewed
The biggest problem in tube audio is getting a decent set of transformers at a reasonable price. Some of the boutique brands are overpriced and overhyped and at least one is incompetently constructed (legal threats prevent me saying which one). As explained elsewhere in these pages, smart buyers go to the suppliers of transformers to the broadcast industry, like Lundahl of Sweden. There they will get modern windings (in Lundahl's case cut C-cores) of very great quality that have had all their development costs paid for by the broadcasters and are thus relatively cheap to the hobbyist. Or they go to the makers of modern toroids who supply the big tube amp manufacturers, in North America Plitron of Canada, in Europe Amplimo of The Netherlands, both of whom employ Menno van der Veen, the world's leading audio toroid designer, to create their audio lines. That quality of design, development and construction is outwith the reach of the boutique brands, and, sadly, of the hobbyist unless he is so expert that he doesn't need the sort of help offered in these pages.
Truly adventurous souls might consider winding their own. It is not rocket science, despite the best efforts of the boutique winders to invest an industrial artifact consisting of a few laminations, some tissue paper and a few metres of wire with the mystique of sultry eastern promise. The problem is not getting good information. The RDH, reviewed on this page, has a worthy section on calculating and designing transformers, and passim tells one which transformers work best and why, but it is reference book, not a do-it-yourselfer's how-to book. Much of the rest of necessary information is hidden in multi-volume texts of American turgidity with lashings of that bow-wow obscurantism some engineers delight in. "Written by engineers for engineers," is no recommendation of comprehensibility to anyone else!
The problem, for those who do not wish to become theoretical magnetics experts, is getting information which is practically and directly useful to winding one or two custom transformers.
Now that problem is solved. Try these, in order of level of application:
Coll design and construction manual by B B Babani
Transformers and Tubes in Power Amplifiers Menno van der Veen
Lab Report: Specialist Range Menno van der Veen
Radio Designer's Handbook, Langford-Smith's famous RDH
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