In those days, condenser microphones were exclusively foreign-made, and audio experts (such as filmmakers and NHK's sound engineers) swore by foreign brands and would not look at any local product. This was understandable, for Japan has very hot and humid summers, and the accepted verdict was that no condenser microphone made under these conditions would function properly. It would give out nothing but noise and be utterly useless.
Nakatsuru exclaimed,"This is nonsense. If no one else will make a local product that works, then it is up to Sony." Knowing he faced a tough task, he went to work.
The immediate impetus came from Heitaro Nakajima of the NHK Science and Technical Research Laboratories. At the time, Nakajima's laboratory was also working on a prototype. This, the very first condenser microphone built in Japan, had a celluloid diaphragm silver-plated on one side. Unfortunately, however, it was prone to emitting noise and when the voltage was too high the celluloid would burst into flames. Thus the project was discontinued.
Nakatsuru learned from Nakajima and by studying German microphones.Though less spectacular than US models, the German ones generally gave the impression of being solidly built, something that appealed to Nakatsuru.
The first problem was the diaphragm. Nakatsuru tried all kinds of materials without success. Then a DuPont product, a polyester material called "Mylar," was imported. He thought this looked feasible, but he had no idea how he was going to apply the pole plate to the Mylar. He finally hit upon the idea of applying gold, but could not see how it could be done. It was Ibuka who put him on the right track. He had an acquaintance who had developed the sputtering technique. Nakatsuru made repeated trials,converting the gold to a form of vapor and depositing or "sputtering" this onto metal, until he was convinced it would work. The first problem was solved and he now had his diaphragm (film).
Next, how was Nakatsuru going to incorporate this into the audio equipment? These were structural questions and involved problems in mass production. The microphones required a vacuum tube of a special type. The Germans used a small triode made by Telefunken, the AC-107 costing 7,000 yen apiece. Using them would price the microphone out of the market. There was nothin to do but look for a very ordinary tube. The one he chose from the many tubes available was a pentode called 6A-U6, which he tried using as a triode connected to a plate and grid. It worked. Now at last he had a prototype C-37.
Nakatsuru marveled at the way breakthroughs came when he persevered --- as well as how far he had progressed.
There was one last obstacle: structural decisions involving the capsule design. In those days, one did not plan to stamp out the form on a press. The envelope would have to be virtually handmade by soldering mesh over the front and fitting the two halves together. Somehow or other, it began to take shape.
When shown the finished prototype, Ibuka's contented response was "We have to advertise. Let's print the name Sony across the middle." The microphone was subsequently used widely by both NHK and commercial stations, and as its debut coincided with that of TV, it played a considerable role in advertising Sony, just as Ibuka had hoped.
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