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Build Your Own Professional-Grade Audio Amp on the Sort of Cheap

Get amazing stereo sound with 3e Audio’s Class-D amplifier board

4 min read
Photo: Randi Klett
Photo: Randi Klett

Years ago I decided to see how little I needed to spend to build a high-end, audiophile quality, class-D amplifier. The answer, then, was US $523.43. I built a worthy little amp, and the article I wrote about it for IEEE Spectrum still attracts page views, and even sporadic emails from people asking where they can get the parts.

Sorry folks, the main components are long gone. So I've been steering people to excellent class-D amplifier kits from Class D Audio, DIY Class D, and Ghent Audio instead. But a couple of months ago I got the itch to see how much better I could do now, almost a decade later, with the same challenge. Part of my motivation was the annual Best Stereo Amps lists from gadget-review website The Master Switch. The lists are dominated by amps costing more than $1,000 (nine of them cost more than $2,000).

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Economics Drives Ray-Gun Resurgence

Laser weapons, cheaper by the shot, should work well against drones and cruise missiles

4 min read
In an artist’s rendering, a truck is shown with five sets of wheels—two sets for the cab, the rest for the trailer—and a box on the top of the trailer, from which a red ray is projected on an angle, upward, ending in the silhouette of an airplane, which is being destroyed

Lockheed Martin's laser packs up to 300 kilowatts—enough to fry a drone or a plane.

Lockheed Martin

The technical challenge of missile defense has been compared with that of hitting a bullet with a bullet. Then there is the still tougher economic challenge of using an expensive interceptor to kill a cheaper target—like hitting a lead bullet with a golden one.

Maybe trouble and money could be saved by shooting down such targets with a laser. Once the system was designed, built, and paid for, the cost per shot would be low. Such considerations led planners at the Pentagon to seek a solution from Lockheed Martin, which has just delivered a 300-kilowatt laser to the U.S. Army. The new weapon combines the output of a large bundle of fiber lasers of varying frequencies to form a single beam of white light. This laser has been undergoing tests in the lab, and it should see its first field trials sometime in 2023. General Atomics, a military contractor in San Diego, is also developing a laser of this power for the Army based on what’s known as the distributed-gain design, which has a single aperture.

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