Tiny Tubes

The forgotten electronics invention that anticipated our insatiable desire for smaller devices

A great way to think about just how much the miniaturization of electronics has helped us as a society is to consider the AirPod and its recently promoted side-use as a hearing aid. These devices are so tiny that there’s no truly non-destructive way to open them up to see what’s hiding inside these tiny devices.

You put it in your ear. You connect it to your phone. It just works—and most people would not be aware of how much technology went into making that interaction seamless for the wearer.

“Seamless” is not a description often used to describe hearing aids, though they’ve come a long way in the roughly 150 years since electronic hearing aids came into use. These devices were large and not particularly portable. The mechanism often lived in your pocket, not near your ear.

The first step to make hearing aids suck less came in the late 1940s, with the invention of the transistor at Bell Laboratories. Hearing aids were one of the first devices that got to take advantage of the transistor’s benefits. But going back to our hypothetical, what happened before we got the transistor?

Short answer: We saw vacuum tubes reach the upper limits of their capabilities. Just as all sorts of other technologies shrank to meet the market need, so too did the vacuum tube.

In the mid-1930s, Raytheon developed a small, efficient vacuum tube variant called the subminiature tube, which effectively allowed the basic function of a vacuum tube to fit in a container about the size of half a cigarette. It was often smaller than a single AAA battery, but compared to what eventually replaced it, the device was still quite large.

But quite large was still small enough to work with for its key use cases.

Raytheon wasn’t alone in shrinking vacuum tubes—the similarly diminutive acorn tube, named for their rough size and appearance and first commercially sold by RCA in 1935, was earlier—but their work was pivotal. Driving its internal innovation were two sharply diverging goals—to offer a technology that could meet emerging military needs, and to support the needs of consumer goods like hearing aids.

The hearing aids came first, which ensured that these tiny flattened tubes, at least for a while, would be known as “hearing aid tubes.” (Not a great name for marketing anything else besides hearing aids, but for a while, it stuck.)

Two key figures in Raytheon’s history helped bring the company’s subminiature tubes to life: Percy Spencer, later famous as the accidental inventor of the microwave oven, and Norman Krim. The more-junior Krim, just a couple years out of college, did have a pedigree of sorts, having studied with Raytheon co-founder Vannevar Bush at MIT. That pedigree stands out, given that his first pitch to Raytheon CEO Laurence K. Marshall—small tubes for hearing aids—was so modest. But the economics made sense—and so did the market.

Raytheon was not the giant it is today—the team was quite small, and the business a little wobbly. That might explain why Krim nearly defected to RCA, according to the 1974 book The Creative Ordeal: The Story of Raytheon. Good thing he came back:

Norman Krim, after a hesitation during which he resigned from Raytheon, accepted a job with RCA, and then returned to Raytheon within a month, launched another new product with his miniature tubes. Krim made a fast tour about the United States talking to hearing-aid dealers and discovered that market was very anxious for improvement. It was necessary for special production equipment to be constructed before the tiny tubes could be turned out in volume, but an arrangement was made with Western Electric to have these components placed inside W.E.’s hearing aids. This constituted a new and profitable section.

This invention created effectively a small, profitable side business for a company with big ambitions. But this formative work took in new importance during World War II—and both Krim and Spencer found their work in sudden demand. Word of Spencer’s side project creating miniature tubes for his sons’ toy airplanes eventually reached a team developing a proximity fuze for the U.S. military. It was a big project—the proximity fuze was a highly desired weapon at the time—and both Krim and Spencer helped in its development. (The tiny tubes, among many other parts, made it possible for the weapon to explode without a direct hit being necessary.)

Given the high-stress situation the tiny tubes were now being put into, they were modified to meet the stringent MIL-E-1 military specification. The result was that these devices weren’t just small, they were road-tested—and could stand a comically impressive 20,000G of force. And that meant that when the war was over and we were all using microwaves and hearing aids, a much-larger Raytheon was well-positioned to sell miniaturized vacuum tubes by the truckload.

But a funny thing happened on the way to miniature tube dominance—and Norman Krim was at the center of the big shift.

Norman Krim, the transistor, and the transformative power of embracing something you didn’t make

Let’s say you dedicated a huge chunk of your career to a specific type of technology, a technology that made your company a lot of money, and you just learned about something else that was significantly better. How would you handle it?

Would you try to bury the competition? Would you try to poke holes in the technology—or try your best to compete with it? Or would you do the unthinkable, and embrace it?

In the late 1940s and early 1950s, Norman Krim was faced with this decision, having turned his profitable hearing-aid niche into a key part of what was starting to become a major industrial concern, particularly for the military. But he had been hearing word of what was happening at Bell Labs, where a competing group of researchers had been experimenting with semiconductors as a way to amplify electrical signals through solid-state means. Put another way, the team—led by William Shockley—were looking for a way to replace vacuum tubes—and having pretty significant success in doing so.

Krim had been familiar with the work after visiting Bell Labs in the late 1940s. But it was an unexpected meeting of the minds that changed the course of Krim’s work. Shockley and Krim briefly lived together during a military procurement advisory board meeting. Shockley was proofreading a groundbreaking junction transistor paper, and talked about it with Krim.

That added knowledge gave Raytheon an inside lane to an important trend, and Krim didn’t let pride over his history with the vacuum tube stand in the way. Instead he went back to the company’s leadership, convincing them to license the technology from Bell and invest heavily in its development.

And invest they did—putting $2 million into the effort, not a small sum for Raytheon at the time, which almost immediately was converted into nearly $3 million in orders for hearing aids, per The Creative Ordeal.

The move ensured that the hearing aids that Raytheon was developing were even better than their competition.

One 1954 article on the shift, in the Berkshire Evening Eagle, claimed that the transistor “saved the nation’s hard of hearing more than $5 million in hearing aid operating costs during the past year.”

Krim, now a Raytheon vice president, made it clear that the advantages of the new device were so significant that it was pushing hearing-aid customers to upgrade, just as the subminiature tubes had.

“Close to 200,000 of the nation’s hearing aid wearers, out of a total of 1,250,000, have already converted from vacuum tube hearing aids to transistor hearing aids,” Krim said in the piece, “although this radically new type of instrument was introduced only a year ago.”

This relatively tiny market for Raytheon became a consistent winner—and it was only a matter of time before other markets for transistors emerged.

So why are we talking about Krim here and not William Shockley, who actually won a Nobel Prize for this stuff?

It might be in part because of Shockley’s second act. Despite his work in creating a technology that has come to dominate daily life, Shockley became a pariah for his racist and eugenicist views, often shared in public settings. And despite being credited for bringing actual silicon to Silicon Valley, his chaotic management style didn’t help things. As the Wired-owned publication Backchannel reported in 2017, Shockley—whose namesake company crashed and burned in the 1960s—was “the tech industry’s original bad boss.”

(How bad are we talking? Eight of his employees left Shockley Semiconductor Laboratory in 1957 to launch Fairchild Semiconductor, a much more important firm to the history of Silicon Valley. They even have a nickname: The “traitorous eight.”)

The result was that the transistor needed a new champion, and Krim became that champion. When he died in 2011, he received fawning tributes that were mostly about his work in transistors. Shockley, on the other hand, has a page on the Southern Poverty Law Center website.

Despite tipping them off early, Shockley also didn’t endear himself to Raytheon in the years after he won that Nobel Prize, either. From The Creative Ordeal:

Shockley had, after leaving Bell Labs, approached Raytheon and suggested he work for the firm. His terms were $1 million. Raytheon offered to equip a lab for Shockley and guarantee him royalty payments on whatever he developed. But to hand over a cool million was too much. After a month of inconclusive dickering, the genius departed for the West Coast, where he presided over a notable series of changes in the semiconductor industry. Raytheon, still holding its lead in the hearing-aid industry with germanium semiconductors, was not too happy about that.

(I will concede that there are people who might also have negative feelings about the modern-day Raytheon, the one that is primarily known as a gigantic military contractor. But tech history sometimes crisscrosses corners we may feel uncomfortable with. We can’t erase the innovative work Shockley did, and likewise can’t do the same with Raytheon.)

Krim’s work ultimately helped make the transistor even more essential to modern world, setting the stage for later technologies, like (yes) the CPU. Raytheon’s vacuum tube work didn’t disappear right away, however, with its main factory for subminiature tubes shutting down around 1986. In a documentary on the technology that features Krim, factory worker Lydia Mitchell made clear that these tubes meant a lot to her and her coworkers.

“We’re very sad about it because it’s part of our life, and it’s contributed a lot to our life,” she said, adding that they had been hearing rumors that the factory would shut down for decades.

Sentimental value has its limits against the ever-shifting wall of progress, however, and the vacuum tube couldn’t make the climb. It’s to Krim’s credit that he figured this out early and jumped on the right track—which doesn’t make him its inventor, but a worthy voice for innovation in the absence of one that people actually want to point towards.