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The fact that a work is unpublished shall not itself bar a finding of fair use if such finding is made upon consideration of all the above factors ♦ PDF Cover Page ♦ ♦ Verso Filler Page ♦ SECOND EDITION Three ShUnnp • Sixpence Net • �- - ' --.... - '.'- "" Tronsfor ers ond Chokes for the WILLIAMSON AMPLIFIER NATIONAL PHYSICAL LABORATORY REPORT ON TESTS OF TRANSFORMER (Marked: Lab: O tp t, Series Il) u u Tested for: Vortexion Ltd., 257/263 The Broadway, London, S.W.19. , The series resistance and inductance of the primary The series resistance and inductance ofthe primary ,I winding with the secondary winding opcn-circuitcd, winding with the secondary winding short-circuited, was measured at 50 cycles per second with and 20 and of half the primary winding with the oilier volts applied. The room temperature was5 short-circuited were measured at 1,000 cycles halfper The results are given in Table 1. l<'°C. second. About 10 volts were applied. The results are given in Table IL TABLE I TABLE 11 Primary Resistance and Inductance at 50 c/s Resistance and Inductance at 1,000 c/s Voltage Resistance (0.) Inductance (H) Connections Resistance (0.) Inductance (lnH) 1'Ii':�;r�h,,!:�'<In'I' 5 4700 95 K�1I !'rin... ",_ K�U 495 5.3 2. J'ri,,,,,,y .homed. 7900 142 222 5.5 Date .. 2nd JUlIt, 1951. Reference .. E.475.100. This Laboratory Model Transformer Series easily permits 11 6 db more feedback with complete stability than the maximum of our Series 1 which Mr. D. T. N. Williamson described. PRICES Series Output Transformers as above ... Il £7. 7.0 Series Output Transformers I £6. 6.0 Mains Transformers ... £4. 4.0 CHOKES 1O.12H, 150 mA ... ll. £1. 6 CHOKES 30/H, 2e mA £2. 0. 6 Please write for Catalogue WAj5 VORTEXION IJ T I) . 257·263, THEBROADWIIY,WIMBLEDON, LONDON, S.W.l9 Tllepbones: LIBut, 2814 and 6242-3 TdelJ'aml: "VORTEXION. WIlIIIBLE. LONDON' POTTED COMPOUND FILLED TRANSFORMERS & CHOKES WODEN Potted components are in constant demand for the WILLlAMSON AMPLIFIER AND PRE-AMPLlFIER_ note the advantoges Made to the author's exact specification. • Smart appearance and uniform layout . • Absolute Reliability. • SEND FOR FURTHER PARTICULARS AND COMPLETE CATALOGUE. WODEN TRANSFORMER [0· LID I\IIOXLEf ROIlO BIlSTO� STJ\JJS PHONE: BllS TO N 41959 J.T.l. 6 The journal for all radio technicians WIRELESS WORLD is Britain's leading technical journal devoted to radio, television anj electronics - its pages providing a complete and accurate survey of the newest British techniques in design and manufacture. Articles of a high standard cover every phase of radio and allied technical practice, well as the wider aspects of international 3S radio. Theoretical articles by recognized experts deal with new developments, while design data and circuits for every application arc published regularly. Monthly, 25. Annual Subscription, £1 75. Order a regular copy DJ WIRELESS WORLD from your newsagent-to-day. The journal for all advanced workers WIRELESS ENGINEER - produced for research engineers, designers and students in radio, television and electronics - is the international source of information for advanced workers; the journal publishes only original work. It IS served by an Editorial Advisory Board romposed of representatives from the National Physical Laboratory and the British Post Office, and publishes Abstracts and References compiled by the Radio Research Organiza­ tion of the Department of Scientific and l:1dustrial Research. Monthly, 3s. 6d. Annual Subscription, £2 4�. 6d. Your newsagent ,oi/l be glad to supply regular a copy of WIRELESS ENGINEER. See him to-day! ILlFFE & SONS LTD., DORSET HOUSE, STAMFORD ST., LONDON, S.E.l The Williamson Amplifier A Collection of Articles, reprinted frolll "Wireless World," 011 "Design for a High-quality Amplifier" By D_ T_ N. WILLIAMSON (formerly of the M.O. Val"c: Company, now with Ferranti Research Laboratories) Published for • LONDON: ILIFFE & SONS, LTD. The W iIIiamson Amplifier CONTENTS Page Introduction 5 Basic Requirements: 7 Alternative Specifications (April 1947) Details of Chosen Circuit and Its Performance 11 (May 1947) NEW VERSION Design Data: 14 Modifications: Further Notes (August 1949) Design of Tone Controls and Auxiliary Gramophone Circuits 20 (Octoberand November1949) Design for a Radio Feeder Unit 30 (December 1949) Replies to Queries Raised by Constructors 34 (January 1950) Modificationsfor High-impedance Pickups and Long-playing Records 35 (May 1952) 3 Introduction Introduced by Wireless World in '947 as merely onc of a series of amplifier designs, the .. Williamson .. has for several years been widely accepted as the standard of design and performance wherever amplifiers and sound reproduction arc discussed. Descriptions of it have been published in all the principal countries of the world, and so there are reasonable grounds for assuming that its widespread reputation is based solely on its qualities. This hooklet includes all the articles written by D. T. N. Williamson on the amplifier. Both the 1947 and 1949 versions are reprinted. as the alternative output transformer ratios cover a wide range of require­ ments. Modifications and additions include pee-amplifier circuits and an d. unit. with recently published information 011 adaptation bigb­ to impedance pickups and correction for 331 r.p.m. records. We would stress the importance, if the full potentialities of Hle amplifier are to be realized, of following the author's recommendations in detail. Even the .S.A., where several modified versions have in U been descri d, many users adhere to the designer's exact specification be with the original valve types. It is not the circuit alone, but the properties of the valves and such components the output tnlnsfonner, as together with the welding of theory and practice into a rational layout, which produce the results. Editor, Wireless World. , .' The Williamson Amplifier Basic Design Requirements: Alternative Specifications improvements in the operation of the loudspeaker. spectrum (but especially, at the ECENTfield of commercial sound This in turn reconverts the elec· low-frequency end) be substan­ recording ha made prac­ trical waveform into a corres­ tially less than that at medium vc Rticable the reproduction of a ponding sound pressure waveform, frequencies, filters must be wider range of frequencies than which in an ideal system would arranged to reduce the level of hitherto. The useful range of be a replica of the original. these frequcncies be/ore they reach shellac pressings has been ex­ The performance of an amplifier the amplifier as otherwise severe tended from the limited 50-8,000 intended to reproduce a given intermodulation will occur. This c/s which, with certain notable waveform is usually stated in is especially noticeable during the exceptions, has been standard terms of its ability to reproduce reproduction of an organ on from 1930 until the present, to a accurately the frequency com­ incorrectly designed equipment range of some 20-15,000 c/s. This ponents of a mythical Foutier where pelial notes of the order of increase in the frequency range analysis of the waveform. While c / s cause bad distortion, 16-20 has been accompanied by an this method is convenient and even though they may be in­ overall reduction in distortion and indeed corresponds to the manner audible in the sound output. the absence of peaks, and by the in which the mechanism of the (3) Negligible phase shift with­ recording of a larger volume range, car analyses sound pressure wave­ in the audible range. Although which combine to make possible a forms into component frequencies the phase relationship bctweell standard of reproduction not pre­ and thcreby transmits intelligence the componcnt frcquencies of a viously attainable from disc re­ to the brain, the (act that the complex steady-state sound ooes cordings.