The History of Magnetic Tape


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The Magic of Magnetic Tape

This section was contributed by Don Rushin, 3M, Minneapolis

From Hi-Fi to high definition, magnetic tape has been a key element in broadcasting.

"The tape came up to speed, then, opening theme -- Crosby: Blue of the Night; applause; introductory patter -- Crosby and Carpenter; song -- Crosby: My Heart is a Hobo; applause.

"Murdo McKenzie signaled me to 'cut.' I pressed the stop button. There were surely no more than two seconds of silence, which seem more like minutes to me, and then a shower of compliments. One small machine, one of a pair, side-by-side on a makeshift table -- the only two of their kind in the United States arranged to record and reproduce magnetic tape with such remarkable fidelity -- had, in a listening demonstration lasting almost exactly five minutes, upset the entire future of sound recording in this country."

Jack Mullin on his demonstration of the Magnetophone tape recorder to Bing Crosby in August 1947 at the NBC/ABC Hollywood studios.

The beginning

The place: London, England. The date: Sunday, February 25, 1940. Twilight comes early to London at that time of year, and on this particular Sunday, it mixed with fog and smoke from thousands of fireplaces to wrap those unlucky enough to be out of doors. Indoors, in front of hundreds of thousands of hearths, Londoners relaxed with their Sunday newspapers and the wireless. World War II had been a fact of life for nearly six months, but the first bombs had yet to fall. It was the era of the phony war, when Hitler still believed it was possible to form an alliance with right-wing forces in Britain and end the war.

Suddenly, listeners who hadn't tuned their set quite properly heard the familiar strains of "God Save the King." An upper-class English voice announced the inauguration of the New British Broadcasting System. What followed was an evening of popular and concert music, interspersed with "news" programs designed to convince listeners that Germany and England shared the same interests and ideals in the upcoming struggle.

The New British Broadcasting System (NBBS) probably would have come into being anyway, but what really made it work was audio recording on magnetic tape. Tape had existed in Germany on an experimental basis since 1920, and commercially since its introduction at the Berlin Radio Exhibition in 1935. What made the NBBS broadcast remarkable was a new recording breakthrough by two Reichs-rundfunk Gesellschaeft (German radio) engineers. Drs. Otto von Braurmuhl and Walter Weber found that by mixing a very high frequency signal with the audio during recording, the reproduced signals were so good that it became difficult to tell them from the live performance.

NBBS, which used captured commercial transmitters in Luxembourg, Belgium and Scandinavia, relied on tape for virtually all of its programming. It was, therefore, possible to air the same concert at the same hour from all of the stations. British listeners wondered how it was being done.

The Third Reich, however, was not the only country in which experiments with magnetic tape were being conducted. In September of 1944, the Minnesota Mining & Manufacturing Company in St. Paul (known today as 3M), already producing coated "Scotch" pressure-sensitive tapes, received a special request from the Brush Development Company of Cleveland, Ohio. The Brush company was "interested in obtaining tapes coated with an emulsion containing a uniform dispersion of ferromagnetic powder," as the inquiry stated. The Brush Company, under a special Navy Department research contract was -- along with 3M -- about to launch the era of magnetic tape.

The first try

Brush agreed to supply the powder if 3M would apply it to a sample stripe of backing so it could be tested. The task was handed over to Dr. Wilfred Wetzel who was unaware of the work that had been done in Germany. One of the first problems he faced was that the oxide supplied by Brush turned out to be nothing more than iron, and that once applied to a paper backing it continued to rust, changing its chemical and magnetic properties.

Another was that 3M had no recorder; not even a recording head, and Brush was being somewhat secretive about what the end product would be used for. Whatever the purpose, Wetzel realized that the coating would have to be smooth if it were not to wear out anything it came in contact with. So 3M scientists, under Wetzel's direction, tried a number of techniques for gluing the particles onto quarter-inch strips of paper eight to ten inches long. As fast as they did so, the samples were mailed to Brush.

In 1944, no one in the United States had yet made a magnetic tape recorder. Wire recorders, using the principals of magnetic recording (patented in 1898 by Poulson), were being used for some business dictation. Even greater interest, however, was shown by the U.S. Navy Department, which was using them to record what they could intercept of German U-Boat radio messages. Much better quality recording was needed, and that was the goal of the Navy Department research contract with the Brush Company.

By late 1944, the World War II Allies were aware of the magnetic recorder developed by German engineers, a recorder that used an iron-powder-coated paper tape, which achieved much better sound quality that was possible with phonograph discs. A young Signal Corps technician, Jack Mullin, became part of a scavenging team assigned to follow the retreating German army and to pick up items of electronic interest. He found parts of recorders used in the field, two working tape recorders and a library of tapes in the studios of Radio Frankfurt in Bad Bauheim.

Almost simultaneously, 3M physicists and chemists were developing for Brush and the Navy a coated tape with a smooth surface and uniform dispersion of ferromagnetic powder that would withstand being drawn over a magnetic head to record electromagnetic signals. The goal was to produce a tape for high fidelity magnetic recording. By 1945, the first workable magnetic tape product had been developed.

After the war

At the end of the war in August of 1945, the Brush Company informed 3M that its Navy Department contract work was finished, and that further development on magnetic tape was to be conducted directly with Brush. The previous year's research had proved costly for 3M and, as yet, had produced not a cent in revenue; prospects for return were remote. But 3M elected to finance its own research based on the potential for extensive post-war application.

At first, 3M management considered being a contract supplier of finished product to Brush, and perhaps others. But the prospects of being merely a producer, with huge development costs and limited return, did not interest 3M. There was also a growing awareness that other companies were experimenting with tape, and many more were beginning to show an interest in building recorders. 3M decided, instead, to add magnetic tape to the its product line.

As months added up and scores of experimental magnetic tape formulations were tried, funding questions became serious; 3M considered putting the whole project in abeyance because no further orders were forthcoming from Brush. Fortunately for 3M, there were farsighted men at the company who, by force of argument and enthusiastic evidence, kept the project alive and advancing.

3M physicist Wetzel foresaw a broad potential market for magnetic tape. He also concluded that because sound could be recorded magnetically, the step to magnetic television pictures would be highly practical. He saw both requiring tape, which held the potential for much higher signal density than wire or steel ribbon.

In January of 1946, 3M learned that Brush was developing a tape recorder to show in New York. The tape project at 3M accelerated, with binder and backing improvements progressing rapidly. By May 1946, large usable quantities of tape were being produced, tape that would prove to be very helpful to Jack Mullin, the former Signal Corps technician who had scavenged German tape recorders during the last months of World War II. (See also Jack Mullin.)

Enter Bing Crosby

On May 16, 1946, Mullin was scheduled as the speaker at the regular meeting of the San Francisco chapter of the Institute of Radio Engineers, held at the studios of radio station KFRC. A demonstration of the German tape recording equipment had been promised, and the room was packed. Mullin played recordings of an orchestra, vocalists and a pipe organ that he had made on some of the tapes he brought back with him. The reaction was little short of a sensation.

One of those who heard about the demonstration was Frank Healy of Bing Crosby Enterprises. Healy believed that Mullin and his machines might provide the solution to a ticklish problem for the singer. In the 1940's, all programming, at least on the "prestige" networks (NBC, CBS and the fledgling ABC) was done live. Broadcasters and sponsors alike believed that transcribed shows -- those recorded in advance on 16-inch, 33 1/3 RPM discs -- sounded inferior and audiences would resent their "canned" quality. But Crosby, one of the highest-rated performers in the NBC stable, had insisted on freeing himself from the weekly grind of appearing live at the microphone. He sat out the 1945-46 season entirely, and came back only when third-ranked ABC promised to let him pre-record the Kraft Music Hall -- but only as long as the ratings remained high.

To Healy and Crosby's technical director, Murdo McKenzie, that meant recording bits of the show on a series of discs, then re-recording from one to another to produce a finished program. It was expensive, time-consuming, and worst of all, sounded bad -- particularly when one section had to be re-recorded two or three times.

Accordingly, one day in August, 1947, Mullin was called in to record the first Crosby show of the upcoming season on his German equipment, while Healy and McKenzie recorded it on disc. Mullin remembered the historic encounter:

"The most unforgettable moment in my life was the one when I stood before my Magnetophone tape recorder and pressed the Playback button for the first time in the presence of Bing Crosby, John Scott Trotter, and Bing's producers, Bill Morrow and Murdo McKenzie. Everything was at stake. By invitation, I had been present with my colleague, Bill Palmer, to record the first radio show of the 1947-'48 season in the NBC/ABC studio complex in Hollywood. And now we were to hear the result of our efforts and be judged by perhaps the most critical ears in the world of radio and recording.

"Prior to our invitation to come to Hollywood from San Francisco to record, and possibly, just possibly, to edit our tape into a complete show, the producers had looked into every alternate means of recording sound that showed any promise of success. Mostly, these boiled down to variations of disc recording methods and photographic sound-on-film systems. I am sure ABC held out little hope for success in testing our apparatus.

"The result of the (very successful) demonstration was that the Crosby people wanted me to stay right there and go through an editing process, to make a broadcast out of it. I did," Mullin told a reporter, "and they saw how easy it was with tape. The next thing I knew, I had a job recording the Bing Crosby Show for the rest of the season."

The problem was that Mullin had only his two rebuilt German recorders and 50 reels of German recording tape for the task. Luckily for him, 3M was working on a commercial product with a backing of acetate film rather than paper.

Mullen also faced another problem -- the 3M tape was "too good" for the German machines, which couldn't handle the tape's higher coercivity. Wetzel and his associates went back to the lab to come up with a tape that would work on the old machines, and on the 12 audio recorders Ampex Corporation was rushing to complete for the American Broadcasting Company. Crosby had been instrumental in persuading the network to buy the machines, copied from Mullin's German originals.

It's worth noting that when the Kraft Music Hall aired on the night of October 1, 1947, it was broadcast from a 16" disc rather than from the tape Mullin had recorded in August. McKenzie and his crew, after having assembled the show from Mullin's master tape, put it on a disc for on-air playback. After one or two shows, they decided to gamble on broadcasting directly from the tape; but just in case the tape should break there was a musician standing by in a nearby studio ready to go on the air with a piano recital.

That practice persisted not only at network studios but also in the studios of larger stations around the country for a year or two, until broadcast engineers discovered that tape simply didn't break. Once ABC began to switch to tape, it made two copies of each program and started them simultaneously on playback decks. If one were to fail, the engineer had only to switch to the backup, missing hardly a syllable.

Tape catches on

ABC's love affair with magnetic tape soon spread to the other networks, who planned to use it to facilitate the switch from standard to daylight savings time at the end of April 1948. The radio networks were thrown into turmoil earlier that year when Congress voted to let the individual states decide when -- and if -- they would go on daylight savings time. For a historic 22 weeks ABC pre-taped 17 hours of network radio programming daily to be replayed at periods appropriate to widely varied time zones.

When 3M began delivering tape, it was only in limited quantities. Everybody wondered whether the tape supplier would be able to meet the April deadline. Somehow they did -- but just barely. Mullin, in order to make his 50 reels of German tape last until reinforcements arrived, saved every scrap, every edit, and spliced them together for reuse. Splicing tape at the time meant "Scotch" sticky tape with a dusting of talcum powder. Mullin remembers checking each splice on a just-broadcast reel, then reassembling the tapes for use again during the next week.

Very much the same thing happened at the ABC studios in Chicago when the network got its first recorders. After the network signed off at midnight, a pair of 3M technicians went to work checking every splice in every tape so they could be reused the next day. Somehow, they managed to finish just in time for sign-on the following morning. During the 22 weeks this routine went on, the station lost only three minutes of air time because of a tape or splice failure.

The introduction of Scotch 100 magnetic tape in 1947 launched the recording tape industry in the United States. Initially, it took a lot of tape to reproduce a limited amount of sound. Broadcast tape recorders in 1947 operated at speeds of 30ips. By 1949, decent quality could be obtained at 7 1/2ips, a 4-fold improvement. That speed is still the industry standard.

A historical footnote -- although ABC had been the first network to embrace recording tape, it was one of the last to put full confidence in it as an archival medium. When Lee Harvey Oswald fired at President John Kennedy in Dallas, TX, on November 22, 1963, ABC engineers realized that history was being made. They dusted off the transcription turntables and captured all of the events of that long weekend on a series of discs. Other networks recorded their coverage on tape. It was the last hurrah of the electrical transcription.

Fear of tape breakage was ever-present in those early days -- not because it actually did, but because of a history of breakage with some tape forerunners. Even Mullin, who knew the medium better than anyone else, was never sure how his splices would hold up to the high tensions of those early recorders.

In the 1930's, the British Broadcasting Corporation had acquired several Blattnerphones, recorders that used ribbons of steel as the recording medium. Editing was done by cutting the ribbon with tinsmith's shears and soldering it back together. Occasionally, the soldered joints would come apart and engineers dove for cover as the steel strip thrashed about. One of the problems with the paper tape used on the early Brush Sound Mirror recorders was that it couldn't stand up to the fast braking of the machines.

Gradually, the musicians hired to stand by disappeared and transcription turntables began to gather dust. Tape moved from the control room to the recording studio, where it was to have a profound effect on all forms of music and on the nation's listening habits. And just as 3M and Ampex had met the Crosby and ABC deadlines, they were able to meet the daylight saving deadline of 1948, if just barely.

Recording pictures

While 1948 was audio tape's big year, it was also the year when 3M engineer Bob Herr proposed the idea of recording pictures as well as sound by using a wide tape at a speed of 15ips past a rapidly-rotating head assembly. Nothing much came of it just then. When 3M's Wetzel demonstrated the first black and white video recordings in 1950, it was with a fixed-head brute-force recorder that consumed 7,000-feet of tape in 15 minutes.

Videotape's big day was April 15, 1956, when the 31st annual convention of the National Association of Radio and Television Broadcasters (NAB) opened at the Conrad Hilton Hotel in Chicago. Ampex planned to show its video recorder, the Mark IV (a forerunner of the production model, the VR-1000). 3M had supplied instrumentation tape as the recording medium.

The day before the show was to open, one of the Ampex staffers decided to try out the new tape. With horror, he discovered that it just wasn't up to the high-frequency demands of the Mark IV and placed a phone call to Dr. Wetzel in St. Paul. Ampex had been cagey about what kind of machine the tape was to be used on, no doubt fearing that 3M might jump into the video recorder business on its own.

Because Wetzel had been doing his own research on video tape, he had a pretty good idea what Ampex was up to. Nonetheless, the Ampex engineer, out of desperation, was forced to outline in detail exactly what the new tape was supposed to do. Could 3M do it -- and in time for the debut the following day? Wetzel thought so, and put a team of technicians on the job. They worked through the night, coming with sample after sample.

Finally, by 6:00 a.m., they'd produced a sample that worked and coated two five-minute reels worth of it. But Wetzel had already left for the airport. Vic Mohrlant, a technical services engineer grabbed the samples and dashed to the airport hoping against hope that Wetzel's flight had been delayed. For once, it had not. It was out on the runway waiting to take off.

Mohrlant dashed out onto the tarmac, found a member of the ground crew who had a pole long enough to reach the cockpit, and persuaded the pilot to stop. Fastening the package onto the end of the pole, he shouted that it was an emergency package for Dr. Wetzel aboard the flight. The pilot, not doubt concerned about a medical emergency, pulled the pouch off the pole and passed it back to his passenger.

The demonstration on April 15 caused the same kind of sensation that Mullin's IRE session had ten years earlier. Hard-headed engineers and front office men were on their feet cheering as the first reels rolled on the Mark IV. Many rushed to the stage to get a closer look. And orders for both tape and recorders piled up.

Videotape goes to work

The first commercial reel of Scotch 179 videotape went to CBS. The network used it to record Douglas Edwards and the News the night of November 30, 1956, for delayed broadcast in the Central, Mountain and Pacific time zones.

History was about to repeat itself. All three networks had decided to make the changeover to daylight savings time on April 28, 1957. Again there was a mad rush to produce enough recorders and enough tape to make this possible. In fact, by April 28, the networks had no more than 50 usable reels among them, each with a price tag of $248.95.

This time, there was no concern among professionals about the possibility of tape breakage -- but there were other worries. That would happen if a reel of the stuff containing an important program were placed in a magnetic field, or stored on top of a radiator or warm studio console? What effect would it have on unionized jobs?

What they weren't concerned about, however, were the effects of dust and dirt. One of 3M's biggest problems in meeting the April 28 deadline had been in coming up with perfect reels of tape. The smallest scratch, a wayward speck of dust or dirt in the coating, or microscopic damage to the tape edges were enough to reject a reel of videotape; in early runs, two-thirds of those produced had to be thrown away.

To keep dirt out and reduce the effects of humidity, the company packed its videotape in sealed transparent polybags. Yet stations and networks, used to handling film, asked for a return to the foil-lined black paper wrapping that had been used for film. Eventually, they learned the hard way that when it comes to videotape, cleanliness is more than just a fetish.

The use of videotape spread rapidly for delayed broadcast and news applications. It was slow, however, to catch on in program production and the shooting of commercials, despite its advantages and economies. One reason was the editing process, which was significantly different than film. Electronic editing still lay many years in the future.

The "Kitchen Debate"

By the summer of 1959, videotape had become as accepted a part of television as audio recording was of radio and the music industry. That summer, the U.S. Information Agency had set up an exhibition in Moscow that included, among other things a model American home -- complete with well-appointed kitchen -- and a color television studio, with its own video recorder. On July 24, Vice President Richard Nixon invited Soviet Premier Khrushchev to visit it with him. Khrushchev found the TV studio fascinating and readily agreed to step before the color camera to make a few remarks, then see himself played back on tape. Nixon joined him and before long the subject had turned from lighthearted pleasantries to a full-blown debate on the relative merits of capitalism and communism.

Oblivious to the red eye winking at them from the front of the camera, the two progressed to vigorous thrust and parry. An Ampex official in attendance reminded them of the tape, which continued to run. Khrushchev, shown how to operate the controls of the recorder, rewound the tape and played it back. Nixon persuaded him to let it be seen in the United States, but Khrushchev insisted that it be translated in full and played unedited. To make sure that it got out of the Soviet Union, Ampex International president Philip Gundy rushed back to his hotel with the tape, wrapped it in a dirty shirt and booked the first flight home.

By the time it was broadcast the following day, American newspapers had reported the event as an exchange acrimonious enough to start World War III. What viewers actually saw, though, was the two leaders in earnest and sometimes animated discussion, but by no means ready to launch missiles. The tape has been hailed as a milestone in communication as well as an historical document in its own right.

One thing the history of magnetic tape teaches us: The more things change, the more they remain the same.


  1. Mullin, John, "Discovering Magnetic Tape," Broadcast Engineering, Intertec Publishing, Overland Park, KS, May 1979.

  2. Ziff, Richard, "Magnetic Tape's Impact on Broadcasting," Broadcast Engineering, Intertec Publishing, Overland Park, KS, May 1979.

Historical Photos

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A well-worn transport assembly of a German Magnetophone tape recorder. This machine was one of those brought back to the U.S. by Jack Mullin. (Courtesy of Ampex.)

The March of Progress

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In this 1947 photo, Jack Mullin (left) shows his modified Magnetophone tape recorders to Murdo McKenzie, Bing Crosby's technical producer. Mullin's ability to edit on his high fidelity German recorders without noticeable generation loss created a sensation in American broadcasting. Mullin's machines later inspired the Ampex model 200. (Courtesy of Ampex.)

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Ampex chief engineer Harold Lindsay checks out the first American professional audiotape recorder, the model 200. This machine was first used by ABC in 1948. (Courtesy of Ampex.)

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Magnetic recording tape pioneers Jack Mullin (left) and Frank Healey (with glasses) discuss early tape programs edited for the ABC Philco Hour radio program with Bing Crosby (right). Crosby was an avid proponent of tape recording, and his ABC network show was the first nationally broadcast tape program in the United States. (The fourth man in the photograph cannot be identified.) (Courtesy of 3M.)

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Bing Crosby, recording a radio program segment in the early 1950s on an Ampex 600 recorder using Scotch Number 111 tape. (Courtesy of 3M.)

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A scene from the famous "Kitchen Debate" between then Vice President Nixon and Soviet Premier Khrushchev in Moscow (July 1959). The encounter was captured on videotape and replayed later to 72 million American home TV viewers. The event brought prominence to the technology of "live" playback from a strip of magnetic tape. (Courtesy of Ampex.)

For more information on Broadcast Engineering magazine, contact Intertec Publishing Corp. (click on the logo).

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