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was not exactly an overnight event. From its introduction in 1898 as the Telegraphone wire recorder to the controversy to today's digital technology, magnetic recording has gone through stormy times.

Valdemar Poulsen, the Edison of magnetic recording, invented almost every known form of magnetic storage. His first idea in 1896 was a magnetic version of Edison's cylinder phonograph.
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Poulsen spiralled piano wiry around a brass cylinder, with a laterally-moving magnetic pick-up head pushed along by the rotating cylinder. Playing time was thirty seconds. By 1899, the Dane (der Däne) had developed magnetic recorders that used spools pulling wire past the record head at two meters per second, with a recording time of several minutes.

Poulsen also made a machine that used a steel band to record sound. He even made a magnetic disc recorder whose pick-up head moved along a spiral guide, very much like the magnetic disc video slow-motion recorders developed by Ampcx and others in the 1960s. And all this before 1900!

Unfortunately, marketing people regarded Poulsen's technical breakthroughs in magnetic recording as a curiosity, a toy. In 1905 the Danish engineer sold his Telegraphone patents to the highest bidder and went on to do research in other areas of electricity, including radio transmitters.

Lee DeForest, the inventor of the modern vacuum tube, wanted to perfect magnetic recording - many of DeForest's early Audion tube diagrams used a wire recorder as the theoretical sound source. However, DeForest's efforts were frustrated by lack of cooperation from Poulsen's successor, the American Telegraphone Company.

For shipboard radio recorders in the 1920s, U.S. Navy researchers Carlson and Carpenter improved the Telegraphone with vacuum tubes, and added something new to the record circuit - called AC bias. But their Navy sponsors lost interest in communications recording and the two were forced to drop the project.

Had the Navy had a bit more foresight (Weitsicht) (easy for us to say today), we might have had relatively high fidelity magnetic wire recording as early as 1923. The Navy's reaction reflected an attitude that continued from Poulsen's day: magnetic recording was more a curiosity than a practical tool.

The next attempt to commercialize magnetic recording was made almost a quarter-century after Poulsen, when Curt Stille in Germany formed the Telegraph Patent Syndicate in 1927. Stille envisioned magnetic recorders for dictation, automatic telephone answering, and even music reproduction. None of the members of the syndicate was very successful in their attempt to commercialize magnetic recording, although the Lorenz Company in Berlin almost succeeded.

Around 1933, under the direction of S. J. Begun (who later headed Brush Development in Cleveland- Anmerkung : Stimmt so nicht, er war Chef der Magnetband- entwicklung aber nicht Chef von Brush Development insgesamt.), the Lorenz Company began work improving one of Curt Stille's ideas, using a steel band as the recording medium. Lorenz had enough faith in magnetic recording to design its "Steeltone Tape Machine" for use in radio stations as a transcription device.

In fact, by the mid-1930s, several European radio services, including the Germans and the British, had used steel recording on the air. Steel-band recorders had reached a quality level almost equal to the broadcast wax disc.

During the world-wide depression of the 1930s, people relied increasingly on radio at home for entertainment. For broadcasters, the Thirties was a time of tremendous growth in entertainment programming. Most radio stations used recording lathes (Schneidemaschinen) to cut lacquer or very thick wax discs for use in time-delayed broadcasts. However, the wax discs could only be played two or three times before the grooves were worn. Also, the radio engineer could not easily edit a program recorded on a disc. The necessary disc-to-disc transfers to edit out mistakes led to high generational loss of sound quality.

Naturally then, magnetic recording on a long, thin strip of material offered the broadcaster editing and multiple-replay capabilities that he did not have with discs. But the Lorenz Company's steel-band recorder was out of date before they could get their machine to the broadcast market. Steel as a recording medium was impractical at best. You edited with solder and a welding torch. A fifty-minute reel of steel tape measured over two feet in diameter, and weighed almost 40 pounds! (20 Kilo)

The machines could even be dangerous for their operators. The English version, the Blattnerphone, used at the British Broadcasting Corporation until as late as 1950, was operated in a metal cage so that if the steel band flew off its reel during fast-forward or rewind, the engineer on duty wouldn't lose a hand, or worse.

We have no figures on the cost of solid steel tape, but the expense was high enough to prompt the German radio service's chief engineer H. J. von Braunmühl to look for an alternative to steel. There had to be a better answer to magnetic recording than the steel band.

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In Dresden, Germany, the "Universelle Company" had been building cigarette manufacturing machines since the turn of the century. One of their engineering consultants in the 1920s was Fritz Pfleumer, whose previous discoveries included drinking straws made of plastic, as well as new forms of foam rubber.

One of Universelle's machines was designed to make cigarettes with a thin band of real gold around the mouthpiece. Even for 1928, using gold on cigarette mouthpieces was becoming expensive, so the company put Pfleumer to work finding a substitute for the gold. Pfleumer developed a bronze powder that he mixed with lacquer, spread on a wide, long strip of paper, and then slit into tiny pieces for gluing onto the cigarettes.

Pfleumer was somewhat of an audiophile. He liked good quality radios and recording devices, and did much experimenting on his own. Of course, like most engineers, Pfleumer knew about the wire Telegraphone and the early experiments with steel-band recording.

Around 1928, Pfleumer was in Paris on a business trip. While sitting in a cafe, he was thinking about magnetic sound recordings. He reasoned that, instead of using expensive, heavy steel tape for recording, he could use his cigarette-mouthpiece-label technique to make cheap, lightweight magnetic tape. Instead of bronze powder, iron powder could be mixed with lacquer and spread on a paper tape.

Pfleumer's combined knowledge of paper tapes from his cigarette work, and his understanding of magnetism and electro-acoustics was crucial to his success in making the world's first magnetic tape recorder. He knew, for example, that the iron particles had to be as small as possible to achieve the highest possible frequency response.

For Pfleumer, the all-important binder material to glue the particles to the tape was no problem at all. He just used the same lacquer he had used for the bronze on the cigarette mouthpieces.
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Pfleumer's first tape recorder, built in 1928-29, sounded just awful: distortion, background noise, wow, and flutter. But the point was, the thing worked! One did not need a solid piece of ferrous material to record sound magnetically. The engineer described his recording tape as "a 300-meter-long roll of the recording material which lasts twenty minutes and costs only one Mark 50 Pfennigs (about 25 cents) to make. The paper, called Pergamine, is only 0,04 mm thick," He pointed out that, with his new recording system, the tape editor could trade his welding torch for a pair of scissors.

Unhappily for Fritz Pfleumer, the German patent office in 1936 denied him his 1928 patent, finding the American J.A. O'Neill's 1927 magnetic tape patent valid. As far as we know, O'Neill never did make workable magnetic tape or a recording device of any kind.

In 1929, Pfleumer took his invention from Dresden to Berlin, to sell it for development. Newspapers there ran stories about the new recorder, alter several private demonstrations. AEG (Allgemeine Eletricitaets Gesellschaft, or "General Electric Company") in Berlin, today affiliated with Telefunken, was Germany's second-largest electronics company, after the Siemens Company.

AEG designed and manufactured professional and consumer electronic products, much as its business assocrate General Electric did in the United States.

At AEG in 1930, Pfleumer's first demonstration of his tape recorder, which he called a "sound paper machine," was less than convincing. This magnetic recorder, like others before it, sounded poor.
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However, for the first time in history, engineers and managers were far-sighted (weitsichtig) enough to see the potential for tape recordings. By 1932, AEG had signed a contract with Pfleumer to buy his patent outright and develop tape recording.

The engineers at AEG tried to make their own tape at first, according to one account, buying carbonyl iron at the corner drugstore and spreading it on paper "ticker tape."

The sound they got from the tape was terrible, and they soon realized that the problems of spreading thin coals of iron-filled lacquer onto strips of paper tape were best left to a chemical concern.

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In the early 1930s, the chief executive officer of AEG, Herman Buecher, heard about his engineers' problem. He called his old friend in Frankfurt, Carl Bosch, who was the head of the powerful "IG Farben chemical combine", to see if the two companies could make the development of the magnetic tape recorder a joint venture. In 1932, AEG's Buecher and IG Farben's Bosch arranged for a member of the IG Farben group BASF, ("Badische Anilin und Soda Fabrik" or "Baden Anilin [dye] and Soda Factory"), in Ludwigshafen, to begin intensive research into the problems of making good magnetic tape for the new AEG machine that they called the "Magnetophon".

The first BASF tapes made in 1934 for the Berlin Radio Show were made of pure, powdered carbonyl iron. The iron, which looks like black dust, was mixed with lacquer and spread onto a cellulose acetate film, which was then cut into five millimeter-wide strips (6.35 mm = 1/4 inch) several hundred meters long.

• Anmerkung : Dieser und noch mehrere Verständnisfehler oder Übersetzungsfehler tauchen hier recht oft auf. Das deutsche AEG Trägerband (aus Papier) war anfänglich sogar 12,0 mm breit, später nur noch 6,5mm. Selbst die 50 Spulen von Jack Mullin hatten diese deutschen 6,5mm Breite und lösten später eine Menge Konfusionen aus.

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BASF's first tape had no trade name, and was simply called "IG Farben carbonyl tape." Capstan problems with AEG's prototype Magnetophon postponed the planned 1934 unveiling of the new recording process until the Berlin Radio Show the next year.

By 1935, the researchers at BASF had progressed from carbonyl iron to iron oxide with smaller magnetic particles that resulted in better electrical performance. Today's iron oxide tapes are essentially refinements of these early BASF formulations.

At the start of their joint venture with AEG, BASF switched from paper to a cellulose acetate film. The early carbonyl iron tape was brittle, but much stronger than the first paper tapes. BASF's trade name for their acetate basefilm was "Cellite," so they called their new iron-oxide formula tape "Type C." Manufactured through 1942, Type C tape had a rust-colored oxide with a gray backing.

By 1943, BASF had introduced a third kind of tape, Luvitherm or "Type L," a homogeneous tape/basefilm of polyvinyl chloride. Though much stronger than the Type C acetate tape, the PVC did stretch. Type L tape was made by dumping the iron oxide into the PVC vat, and then extruding the mixture into a solid film.

Because the iron oxide was mixed throughout the tape. Type L could be recorded on either side.

Another IG Farben member, Agfa at Wolfen, later joined BASF in the production of recording tape. In 1944-45, American GIs invading Northern Europe found a lot of Type L tape. Both BASF and Agfa were able to steadily increase their tape production until war's end in May of 1945.

The origin of today's one-quarter inch tape width standard came from a combination of good engineering and coincidence. In 1935, just before the introduction of the first AEG/BASF recorder and tape, the companies jointly decided to widen the tape from its original 5.0 mm to 6.5 mm (just a hair over one-quarter inch). The engineers chose the wider tape for greater strength and better electrical performance. We still do not know why they chose the number 6.5 mm.

When the Allied engineers examined the captured Magnetophons and their BASF/Agfa tapes, they measured the 6.5 mm width as a quarter inch, plus or minus "a tiny bit." The 0.15 mm difference between a quarter inch and 6.5 mm was really not worth noticing. With the interruption of German tape manufacturing at the end of the war and the importation of American 3M (Scotch), Orr Radio (Irish), Audio Devices and other tape, the official width of magnetic tape there became 6.35 mm as well.

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Our thirty inches-per-second base type speed also originated in Germany with the Magnetophon. Until 1935, the AEG/BASF R&D team used one meter-per-second as their nominal standard tape speed. However, slight variations from machine to machine in motor performance and capstan diameter made interchangcability of tapes impossible.

In 1935, the selection of a newly-designed asynchronous motor for the capstan drive solved this problem. In an effort to simplify future production of Magnetofones and set a world-wide standard, the engineers specified a capstan diameter of 10mm, ±0. A ten-millimeter capstan with AEG's asynchronous motor and the BASF tape produced a tape speed of 76.8 centimeters-per-second. If the production of the Magnetophons could be standardized, an odd tape speed really would not matter.

When Major Jack Mullin, one of America's tape pioneers, and his U.S. Army Signal Corps engineers measured the Magnetophon's tape speed, they were surprised to measure almost exactly 30 inches-per-second (76.2 cm/s).

Mullin's captured Magnetophons inspired the creation of the Ampex Model 200. Americas first commercially-successful professional recorder, in 1947, Harold Lindsay, the Model 200's chief designer, used Mullin's 30 ips figure in the American machine's design, which later became the U.S. standard.

Mullin had lent Lindsay some of his precious pre-recorded Magnetophon tapes for test purposes, thus the logical choice of a 30 ips tape speed for the American machine.

With the postwar dismantling of the Magnetophon factories, American machine dominated the European recording market in the early 1950s. The Germans adopted the U.S. figure of 30 ips, converting the number back to the metric 76.2 cm/s. No one ever seemed to notice the difference.
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From the start of the Magnetophon project, AEG faced the difficulty of making good heads. Both Pfleumer's and AEG's prototypes used record/reproduce heads similar to those originally developed by Poulson and found on wire and steel band recorders: pole pieces with sharpened points pushed by springs into the surface of the recording medium. Naturally, the pointed head pieces quickly ripped the thin paper apart. Even the later acetate and PVC-backed tapes could not stand more than one pass or two from the points.

AEG's early experiments with the old-style pole-piece heads showed that, in addition to tape destruction, these heads had electrical disadvantages. The magnetic lines of force from the pointed heads with their separate pole pieces were both horizontal (parallel to the axis of the tape travelling past it) and diagonal. The lines of flux which intersected the tape were unfocused and mostly unusable, even interacting with each other to create distortion.
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The solution was an invention by Eduard Schueller: the enclosed ring head. Schueller had worked as a research assistant at the Heinrich Hertz Institute, a technical "think tank" in Berlin, and by 1932 was already experimenting with ideas of magnetic recording. Schueller found that the most important part of successful magnetic recording was the head.

He decided to improve on the open pole piece head design. The result was his experimental ring head. Naturally, as soon as AEG heard about Schueller's work, they offered him a key position on their tape recorder development team.

Schueller's ring head was not only very easy on the early tapes, but also created the nearly ideal magnetic flux pattern necessary for better fidelity recording. The lines of flux were concentrated in their most useful direction, horizontally (in the direction of the tape).

Thanks to the AEG-Telefunken Archives, BASF, the German Radio Archives in Frankfurt, and Hans Westphal of Berlin, we have copies of the earliest recordings made on the AEG prototype recorder in 1933. On the first recordings, the frequency response limit was not more than 3 or 4 kHz, harmonic distortion was about ten percent, and the signal-to-noise ratio was quite poor. By 1935, with the introduction of AEG's first production machine, the "Magnetophon K1," fidelity had been increased, with frequency response to beyond 5 KHz and with less distortion.

Although AEG initialed the development of the modern tape recorder, it was BASF who gave the machine its name. The engineers at AEG in 1932-33 dubbed their new machine "Ferroton."' At BASF, they were calling their tape "Magtophonband" or magnetic phonograph tape. The name stuck, and in 1935, AEG started calling the machine "Magnetophon."

By 1935 the Germans had three ot the four necessary ingredients of modern tape recording:

1. 1) a stable transport, which the steel band recorders such as Lorenz had;
2. 2) good tape, which the researchers at BASF had created; and,
3. 3) the ring head from AEG's Schueller, with its good magnetic properties and gentle treatment of fragile tape.

The fourth element of magnetic hi-fi recording, good electronics, would have to wait until 1939-40, after the Second World War had started.
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From Valdemar Poulsen at the turn of the century until the late 1930s, direct-current biasing was the only method known to European engineers to reduce noise and distortion and increase frequency response. As late as 1939, the DC-bias Magnetophon sounded no better than an average 78rpm transcription disc (Plattenspieler).

Until 1945, most engineers around the world had not heard of the German tape recorder. It was the combination of DC bias and World War II that kept the Magnetophon in obscurity. Jack Mullin has said that, "Once you hear DC-bias recording, you'll never want to hear tape again!"

Sir Thomas Beecham, having heard his London Philharmonic on tape in November of 1936, reportedly was so horrified by what he heard that he didn't use tape again until 1950.

In 1936, AEG sales people took their new Magnetophon to America for a secret demonstration at General Electric in Schenectady, New York. The DC-bias unit sounded so bad to the Americans that they decided that magnetic recording, at least in that form, was not practical.

The most promising market for the then-unperfected magnetic recording machine in Germany in the 1930s was the Berlin-based German radio monopoly, known as the RRG (Reichs Rundfunk Gesellschaft, or Empire Radio Company). The chief of the RRG engineering section, H. J. von Braunmühl, was against using magnetic recording for broadcasting. He liked the tried-and-true wax disc recording lathes with their Neumann heads. However, the progress of the AEG and BASF engineers interested him.

Von Braunmühl bought several DC-bias Magnetophons and put his best engineer Walter Weber, to work to see if the machines really could be improved enough to be used on the air. Meanwhile, the people at AEG were also hard at work trying to perfect magnetic recording.

Weber at RRG had an idea of how to improve the signal-to-noise ratio. He cancelled some of the noise by adding an inverting bridge circuit with a "dummy" record head to the record amplifier circuit. The resulting 180-degree phase shift reduced tape noise about three dB.

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One day in 1939, Weber was experimenting with this circuitry, making recordings of music and speech as well as pure tones. Weber kept logs of which recorder he had used, time of day, and what he had recorded. Later, while playing back one of the tapes, Weber found that the sound was fantastic! He was hearing true high fidelity on tape: extended frequency response, low noise and low distortion. He traced the recording back to a Magnetophon that used his new noise reduction circuit, checked that circuit, and found that it was in constant oscillation, dumping high-freguency feedback into the record circuit. Weber realized that AC record-bias was the answer to hi-fi tape recording. He spent the rest of 1939 and much of 1940 perfecting his AC-bias discovery.

After the boss of the AEG Magnetophon lab across town heard the results of Weber's breakthrough at RRG, he went to his own researchers and said, "What in the world have you guys been doing here, sleeping ? Over at RRG, they've just discovered AC bias and turned our machine into a high-fidelity recorder. We've got to get on the ball here!"

In fact, AC biasing of the record circuit was nothing new. But times were different and engineers often missed each other's progress. Back in 1927, the U.S. Navy engineers Carlson and Carpenter, using a Telcgraphone, had noticed the improvement of AC bias on wire recording - of telegraph messages. About the same time that Weber discovered AC biasing for tape recorders, Marvin Camras of the Armour Research Institute in Chicago had a similar discovery for use with his improved wire recorders.

With the war already in progress in Europe by 1940, it wasn't too surprising that Weber and Camras had not heard of each other's discoveries. In the late 1930s, the Japanese, under Kento Nagai, also discovered the AC-bias phenomenon on solid magnetic material.

After the war, the Allied Commissions in Germany and Japan declared all international patents of the Axis (also Deutschland und Japan) powers invalid. That left the quite advanced Armour patent as the finisher in the post-war AC bias license field.
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For AEG, the beauty of Weber's discovery was that they could take their existing DC-bias design and simply add the relatively simple AC-bias circuit, while changing the record head only slightly. The playback of the DC-bias Magnetophon was quite good, although its full potential was never realized before AC-bias recording.

The last production DC-bias Magnetophon had a specified frequency response of 50Hz- 6kHz, a dynamic range of 40dB and harmonic distortion of 5 percent. The first AC-bias Magnelophon was rated at 40Hz - 15kHz, with a 65dB dynamic range, and harmonic distortion under 3 percent

Most oft the studio Magnetophones in use at the end of World War II were designed as early as 1938. The first production Magnetophon, the portable Kl, appeared in 1935. ("K" stands for the German word "Koffer" or "portable case" or suitcase).

The machine came in three cases, one for the transport (gemeint ist das Laufwerk), another for the electronics, and a third holding the loudspeaker. At the same time, AEG produced the cabinet "FT" series Magnetophon "Ferngesteuerte Truhe", or "remote control cabinet"). The K-2 and FT-2 were introduced in 1936. The only FT-2 in existence that we know of is now a part of the Ampex Museum of Magnetic Recording in Redwood City, California.

The K-3 and FT-3 in 1937 were followed by the final Magnetophon in the pre-1945 series, the K-4, in 1938. The K-4 is the best-known pre-1945 Magnetophon. This is the machine that Jack Mullin and his partner, San Francisco filmmaker William Palmer, used to introduce America to the new technology of hi-fi tape recording.

The 1938 K-4 had DC biasing, and after the introduction of AC bias in 1941, a few early K-4s were updated. AEG also made an agreement with the RRG radio people to deliver K-4 decks built to RRG specifications incorporating the AC-bias design.

The radio station console machines that Jack Mullin first saw at the Radio Frankfurt substation at Bad Nauheim in July in 1945 were special K-4 HTS (Hochfrequenz Truhe Spezial, or AC-bias cabinet special models.)

When the war started, everyone in Germany was ordered to switch over to building military products. That was as true for tape recorders as for coat buttons. AEG produced a very rugged, portable DC-bias version of the Magnetophon that they called the Tonschreiber or "sound writer". The best-known of the Tonschreibers was the Type B or Berta machine, which appeared in 1939-40. Berta was unusual because the machine had an extra, spinning head which could be used to compress or expand sound for high speed transmission of information.

An amazing fact of World War II was that no one on the Allied side seemed to have heard about the hi-fi Magnetophons until the end of the war.

This ignorance is even stranger when you consider that popular German magazines and newspapers publicly sold in neutral Switzerland, printed numerous feature articles about German radio stations.

Had the Germans classified all information about the AC bias Magnetophons as "top secret," the Allied probably would have known about the machines before the end of 1940! As it was, they had to wait another five years.

• Anmerkung : Außerdem gab es von der AEG in Berlin und der BASF (IG-Farben Ludwigshafen) eine in ganz Deutschland angekündigte Presse-Vorstellung des "neuen" bzw. verbesserten AEG "magnetophones" in einem sehr großen Berliner Kino (UFA-Palast am Zoo mit über 2100 Sitzplätzen, später der Zoo-Palast) am 10. Juni 1941.
  Aus einem Archivbuch in Hainichen bekommen wir dieses hier :
  
  
• Im UFA-Palast am Berliner Zoo wird in einer öffentlichen Veranstaltung erstmals ein mit Hf-Vormagetisierung aufgenommenes Tonband vorgeführt (Entwicklung Dr. Walter Weber im Labor der RRG. Das Patent J. von Braunmühl/Weber wurde von der AEG aufgekauft). Tonbandgerät: K 4/HF: Begrüßung: Direktor Dr.-Ing. Hans Heyne vom Vorstand der AEG und Technische Einführung: Dr.-Ing. Schepelmann, AEG. Mitwirkende: Heinrich George, Erna Sack, Fehse-Quartett und das Orchester der Städtischen Oper Berlin-Charlottenburg unter Ltg. von Staatskapellmeister Lutze.

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During World War II, the Allies were sometimes confused about Hitler's location. Live-quality broadcasts of his speeches simultaneously came from all parts of Germany. The Allies suspected some sort of high-fidelity recording device, but they overlooked the fact that the Germans had an extremely advanced radio network. A complex web of high quality Landlines (10 kHz bandwidth, 600 ohm balanced line, less than 1 dB loss per 1000 km) allowed remote broadcasts from any location to any other location. In addition, time delay broadcasts had been standard procedure in Germany since the mid-1920s.

To this day, old RRG engineers are amazed and baffled to hear that Americans thought that the Magnetophons were being used to deliberately confuse the Allies as to the location of high Nazi officials.

In England between 1942 and 1944. Major Jack Mullin and others had been hearing late-night German broadcasts of live-quality orchestral music (das war aber alles noch Mittelwellen-Qualität !!).

Mullin thought that even a mad man like Hitler could not compel tempermental musicians to play at three a.m. However, the audio quality of the transmissions was much better than any recording device Mullin knew.

• Anmerkung : Wie Jack Mulin später vortrug, konnte er sich fast gar nicht oder nur sehr schwer bzw. recht vage vorstellen, daß das die ganze Nacht lang alles Musik-Konserven waren. Ausserhalb Deutschlands hatte man wenig Ahnung von Schallplatten mit 60 Minuten Spieldauer oder anderen Technologien. Für Stahlband war das alles viel zu gut. Und die Sendungen kamen damals alle über Mittelwelle nach England. UKW im Regelbetrieb gab es ja noch gar nicht.
  
  Warum die sogenannten Feindstaaten die Vorführung des HF Magnetophons im Juni 1941 in Berlin nicht mitbekommen hatten, wird ewig ein Rätsel bleiben.
  
  Nachtrag 2018 - es ist natürlich kein Rätsel geblieben. Bei der AEG K4 (das war bereits HF-Version) Vorführung im Juni 1941 im UFA Palast in Berlin war keiner der "feindlichen" Auslandskorrespondenten mehr anwesend. Denen war das Berliner Pflaster "zu heiß" geworden.
  
  Weiterhin stehen in den in 2017 aufgetauchten US-Zeitschriften diverse Wahrheiten, die einen ganzen Teil der bekannten Geschichte relativieren bzw. ergänzen. Diese Infomationen waren den beiden Autoren in 1982 vielleicht gar nicht bekannt, denn die kannten nur die Ampex Archive.
  
  In 2019 bekamen wir sogar einen Intelligence Report vom Nov. 1945, in dem fast alle Magnetophon Modelle bis dato ausführlich beschrieben waren.
  

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What he heard was the routine use of the Magnetophon, which had been developed as a professional and consumer entertainment.
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The Magnetophon tape recorder naturally got sucked up into the German war effort. The chief of the AEG Magnetophon lab during the war, Dr. Hans Schiesser, said that he had received specific orders from the Nazi government to work exclusively on the DC-bias military Tonschreibers for use by the army, air force, and navy, and to ignore civilian tape recorder development.

However, Schiesser kept a secret set of lab notes which he still has, in which he wrote of his work on high-fidelity magnetic recording. Schiesser's work included the development of stereo record and playback heads, which he quietly did on the side, at some personal risk. For Hans Schiesser and many others at AEG and the RRG, the Magnetophon tape recorder was the exciting way into the future of high fidelity reproduction of sound.
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