Historical Development of Magnetic Recording and Tape Recorder 3 Masanori Kimizuka ■ Abstract The history of sound recording started with the "Phonograph," the machine invented by Thomas Edison in the USA in 1877. Following that invention, Oberlin Smith, an American engineer, announced his idea for magnetic recording in 1888. Ten years later, Valdemar Poulsen, a Danish telephone engineer, invented the world's frst magnetic recorder, called the "Telegraphone," in 1898. The Telegraphone used thin metal wire as the recording material. Though wire recorders like the Telegraphone did not become popular, research on magnetic recording continued all over the world, and a new type of recorder that used tape coated with magnetic powder instead of metal wire as the recording material was invented in the 1920's. The real archetype of the modern tape recorder, the "Magnetophone," which was developed in Germany in the mid-1930's, was based on this recorder.After World War II, the USA conducted extensive research on the technology of the requisitioned Magnetophone and subsequently developed a modern professional tape recorder. Since the functionality of this tape recorder was superior to that of the conventional disc recorder, several broadcast stations immediately introduced new machines to their radio broadcasting operations. The tape recorder was soon introduced to the consumer market also, which led to a very rapid increase in the number of machines produced. In Japan, Tokyo Tsushin Kogyo, which eventually changed its name to Sony, started investigating magnetic recording technology after the end of the war and soon developed their original magnetic tape and recorder. In 1950 they released the frst Japanese tape recorder. In the 1960's several cartridge-type tape recorders were developed to meet the requirements of car-stereo devices, and fnally, the compact cassette system was introduced. Japanese manufacturers contributed to improving the basic recording performance of compact cassette recorders and to expanding the variety of available products, especially small-sized tape recorders. As a result, they attained a large market share in the worldwide tape recorder market. In 1979 the "Walkman," a portable compact cassette player, was introduced to the market, and in a very short period it became very popular all over the world. The product concept of the Walkman was well accepted, and it changed the style of audio listening dramatically. In this report I briefly describe the history of sound recording, particularly the progress and relation of magnetic recording technologies in the compact cassette system. I also describe the product concept and downsizing technologies of the Walkman. In the last section, I explain the development of digital audio tape (DAT), an advanced tape recording system that led to the rise of digital audio technology. Japanese audio manufacturers joined the tape recorder market relatively soon after the end of World War II. Around 1970 the technical capabilities of device manufacturers increased rapidly, and many superior devices such as precision mechanical components and high-performance electrical devices became available on the domestic market. The synergy effect between product design and device technologies improved the competitiveness of the fnal products, and Japanese audio manufacturers achieved success in the compact cassette tape recorder market. They changed the style of listening and the audio product itself with their introduction of the stereo-headphone "Walkman" in 1979. They ultimately succeeded in getting a huge market share of the worldwide audio market. Many people have recently been enjoying listening to music supplied in a digitally compressed format with small portable devices and headphones. However, it is hoped that the Japanese audio industry will develop a revolutionary new product or service for a more comfortable listening experience with even better sound. ■ Profle Masanori Kimizuka Chief Survey Officer, Center of the History of Japanese Industrial Technology, National Museum of Nature and Science, Tokyo March 1973: Graduated from the Department of Mechanical Engineering, Osaka University April 1973: Started working at Sony Corporation Involved in the design and development of audio equipment and storage equipment February 2006: Representative Director of Start Lab, Inc. December 2011: Left Start Lab Left Sony Corporation Present: Part-time lecturer at Tokyo University of the Arts Director of Japan Audio Society ■ Contents 1. Introduction ……………………………………………………………………………………………………………… 185 2. Recording Sound ……………………………………………………………………………………………………… 187 3. Invention of Magnetic Recording …………………………………………………………………………………… 189 4. Post-war Tape Recorders …………………………………………………………………………………………… 197 5. Development of Domestically-Produced Tape Recorders …………………………………………………… 206 6. Emergence of Cartridge-Type Tape Recorders ………………………………………………………………… 215 7. Structure and Performance of Compact Cassette-Type Tape Recorders ………………………………… 224 8. Magnetic Tape in Compact Cassettes …………………………………………………………………………… 227 9. Advances in Magnetic Heads for Compact Cassettes ………………………………………………………… 229 10. Development of Three-Head Compact Cassettes …………………………………………………………………… 234 11. Noise Reduction Systems ………………………………………………………………………………………… 238 12. Advances in Driving Motors ……………………………………………………………………………………… 244 13. Towards the "Headphone Stereo" ………………………………………………………………………………… 251 14. Invention of Digital Audio Tape Recorders (DAT) ………………………………………………………………… 258 15. Conclusion …………………………………………………………………………………………………………… 269 Tape Recorder System Diagrams …………………………………………………………………………………… 271 Chronological Table ……………………………………………………………………………………………………… 272 List of Tape Recorders …………………………………………………………………………………………………… 273 1 Introduction Many thousands of years ago, people painted various images practical magnetic recording machine. on rock surfaces. The vivid animal depictions in the famous Just before the Second World War, a magnetic recording Cave of Altamira, thought to have been painted as a ritual machine was proposed in Germany, which replaced the steel to the gods, are still-image records left by the people of the wire with tape, making it easier to use. This was the birth time. Since ancient times, people have dreamt of recording of the prototype tape recorder. While the war prevented sound in the same way as pictures; however, they lacked countries from exchanging magnetic tape recording the means to record it, other than passing it down through technology, research progressed in Germany and the the oral traditions of story and song. When writing was technology continued to improve. By the end of the war, invented, people could record their voices through this the tape recorder was complete, equipped with advanced innovative means of “recording words using letters”. With technology such as AC bias and stereo recording. After regard to music, however, capturing the sound itself held the war, the Allies carried out a detailed investigation of more signifcance than the recording of mere words. People all German technology related to magnetic recording; this devised notation systems as a means to record the sounds of technology then became widely used in the development of music and a number of civilisations had their own notations tape recorders in the United States. Ampex, a small, newly- and symbols for this purpose. However, this “sheet music” founded company, took on the challenge of developing the was still an indirect means of recording music. The recording tape recorder in the United States; before long, it was an of sound itself remained a dream. industry-leading corporation, making major contributions Around the mid-19th century, Frenchman Édouard-Léon to the technical advancement and development of the tape Scott de Martinville devised a machine that could record the recorder. With Europe lagging a little behind the times, changes in a sound waveform against a time axis, based on Studer, a small Swiss company, began to develop the tape the idea that sound is transmitted as a wave. Although Scott recorder there. It developed superior models, from business de Martinville’s machine could record sound waveforms, it machines to luxury consumer products, and became the could not reproduce the recorded waveform as sound. In 1877, leader of the industry in Europe. In Japan, Tokyo Tsushin around 20 years later, American inventor Thomas Edison Kogyo (later Sony), founded not long after the end of the invented the “phonograph”, a machine that could reproduce war, persevered in researching magnetic recording, believing sound by producing a vibration from a sound waveform in its potential. In 1950, the company completed the first recorded on a brass cylinder wrapped in tin foil. For the frst domestically-produced tape recorder in impoverished post- time in human history, a machine could record and reproduce war Japan. After the war, tape recorder technology and its sound. The more advanced gramophone record was a later potential star qualities went public. Venture companies in improvement to the device. This advancement meant that the Japan, Europe and the United States alike took on the tape device could be developed not only as a sound recorder, but recorder challenge, and a number of interesting designs also as a household music player through these records. As emerged. radio broadcasting gained popularity, disc recorders became While tape recorders first gained popularity for business vital pieces of equipment