Vacuum tubes once ruled the world, and they still do when it comes to guitar amplifiers, but by and large tubes seem like they've seen their day in the sun. Except that's not completely true, as there's a magnetron tube inside every microwave, and tubes are still found in communications satellites and even modern aviation radar systems.
In fact, tubes may soon be an integral part of the circuitry in even more equipment, as DARPA (the Defense Advanced Research Projects Agency) has instituted a new program called Innovative Vacuum Electronic Science and Technology (INVEST) to take tube technology to the next level.
Why? Tubes have an unmatched ability to generate high-frequency signals at a power that would melt a solid-state device. We're talking about operating frequencies at around 75GHz. And tubes are impervious to EMP (electro-magnetic pulse) coming from a nuclear blast which would fry solid-state gear.
There are two upsides for the audio business that could come about because of this new program.
1. Tube technology has been fairly static for about 40 years. An improvement in the technology may overcome some of its problems like the heat, efficiency and fragility.
2. Most audio vacuum tubes are manufactured overseas. Since the tubes that DARPA will create will be for national defense, they'll be manufactured in the US, which could open up another source for the tubes we commonly use.
It's pretty cool that tubes may be staging a comeback. It's just another case of what's old is new again.