Drive High-Impedance Headphones With This Stylish USB DAC

October 9, 2021 by Jenny List 3 Comments

For anyone with an interest in building audio projects, it’s likely that an early project will be a headphone amplifier. They’re relatively easy to build from transistors, ICs, or tubes, and it’s possible to build one to a decent quality without being an electronic engineering genius. It’s not often though that we see one as miniaturized as [daumemo]’s USB-C DAC and headphone amplifier combo, that fits within a slightly elongated 3.5 mm jack cover as part of a small USB-to-headphone cable.

The DAC is an off-the-shelf board featuring an ALC4042 IC, it has a line-level output and a handy place to tap off a 5 volt line for the amplifier. This final part is a tiny PCB with two chips, a TPS65135 that produces clean +5 and -5 volt rails, and an INA1620 which is a high-quality audio amplifier set up for 2x gain. All this has been designed onto a very small PCB, which sits inside a 3D-printed housing along with the 3.5 mm earphone socket. The result is a very neat unit far better able do drive high-impedance headphones than the output from an unmodified DAC, but still looking as svelte as any commercial product. We like it.

This may be one of the most compact USB-to-headphone amplifiers we’ve seen, but it’s by no means the first.

Making Coffee With Hydrogen

October 9, 2021 by Jenny List 17 Comments

Something of a Holy Grail among engineers with an interest in a low-carbon future is the idea of replacing fossil fuel gasses with hydrogen. There are various schemes, but they all suffer from the problem that hydrogen is difficult stuff to store or transport. It’s not easily liquefied, and the tiny size of its molecule means that many containment materials that are fine for methane simply won’t hold on to it.

[Isographer] has an idea: to transport the energy not as hydrogen but as metallic aluminium, and generate hydrogen by reaction with aqueous sodium hydroxide. He’s demonstrated it by generating enough hydrogen to make a cup of coffee, as you can see in the video below the break.

It’s obviously very successful, but how does it stack up from a green perspective? The feedstocks are aluminium and sodium hydroxide, and aside from the hydrogen it produces sodium aluminate. Aluminium is produced by electrolysis of molten bauxite and uses vast amounts of energy to produce, but since it is often most economic to do so using hydroelectric power then it can be a zero-carbon store of energy. Sodium hydroxide is also produced by an electrolytic process, this time using brine as the feedstock, so it also has the potential to be produced with low-carbon electricity. Meanwhile the sodium aluminate solution is a cisutic base, but one that readily degrades to inert aluminium oxide and hydroxide in the environment. So while it can’t be guaranteed that the feedstock he’s using is low-carbon, it’s certainly a possibility.

So given scrap aluminium and an assortment of jars it’s possible to make a cup of hot coffee. It’s pretty obvious that this technology won’t be used in the home in this way, but does that make it useless? It’s not difficult to imagine energy being transported over distances as heavy-but-harmless aluminium metal, and we’re already seeing a different chemistry with the same goal being used to power vehicles.

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Hackers And China

October 9, 2021 by Elliot Williams 26 Comments

The open source world and Chinese manufacturing have a long relationship. Some fifteen years ago, the big topic was how companies could open-source their hardware designs and not get driven bankrupt by competition from overseas. Companies like Sparkfun, Adafruit, Arduino, Maple Labs, Pololu, and many more demonstrated that this wasn’t impossible after all.

Maybe ten years ago, Chinese firms started picking up interesting hacker projects and producing them. This gave us hits like the AVR transistor tester and the NanoVNA. In the last few years, we’ve seen open-source hardware and software projects that have deliberately targeted Chinese manufacturers, and won. We do the design and coding, they do the manufacturing, sales, and distribution.

But this is something else: the Bangle.js watch takes an essentially mediocre Chinese smartwatch and reflashes the firmware, and sells them as open-source smartwatches to the general public. These pre-hacked watches are being sold on Kickstarter, and although the works stands on the shoulders of previous hacker’s reverse engineering work on the non-open watch hardware, it’s being sold by the prime mover behind the Espruino JavaScript-on-embedded language, which it runs on.

We have a cheap commodity smartwatch, being sold with frankly mediocre firmware, taken over by hackers, re-flashed, re-branded, and sold by the hackers on Kickstarter. As a result of it being (forcibly) opened, there’s a decently sized app store of contributed open-source applications that’ll run on the platform, making it significantly more useful and hacker friendly than it was before.

Will this boost sales? Will China notice the hackers’ work? Will this, and similar projects, end up in yet another new hacker/China relationship? We’re watching.

When Benchies Fly

October 9, 2021 by Al Williams 5 Comments

Most of us have printed a few benchies to test our 3D printers. The intrepid little boat has a variety of features that tax different parts of the printing process. However, the guys at [FliteTest] had a different idea. They set out in a competition to build a giant flying benchie. They aren’t quite done, but they did make some interesting progress, as you can see in the video below.

In all fairness, the benchies are not, themselves, 3D printed. Foamboard, however, is a bit more practical. Inevitably, you can’t help but think of a flying boat when you see the results.

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Nifty Chip Adapter Does The Impossible

October 9, 2021 by Jenny List 30 Comments

The semiconductor shortage has curtailed the choices available to designers and caused some inventive solutions to be found, but the one used by [djzc] is probably the most inventive we’ve yet seen. The footprint trap, when a board is designed for one footprint but shortages mean the part is only available in another, has caught out many an engineer this year. In this case an FTDI chip had been designed with a PCB footprint for a QFN package when the only chip to be found was a QFP from a breakout board.

The three boards which make up the adaptor — The three boards which make up the adapter

For those unfamiliar with semiconductor packaging, a QFN and QFP share a very similar epoxy package, but the QFN has its pins on the underside flush with the epoxy and the QFP has them splayed out sideways. A QFP is relatively straightforward to hand-solder so it’s likely we’ll have seen more of them than QFNs on these pages.

There is no chance for a QFP to be soldered directly to a QFN footprint, so what’s to be done? The solution is an extremely inventive one, a two-PCB sandwich bridging the two. A lower PCB is made of thick material and mirrors the QFN footprint above the level of the surrounding components, while the upper one has the QFN on its lower side and a QFP on its upper. When they are joined together they form an inverted top-hat structure with a QFN footprint below and a QFP footprint on top. Difficult to solder in place, but the result is a QFP footprint to which the chip can be attached. We like it, it’s much more elegant than elite dead-bug soldering!

A composite of a disassembled and reassembled Model F keyboard

Model F Keyboard Restoration Goes The Extra Mile

October 8, 2021 by Chris Wilkinson 19 Comments

The IBM Model F keyboard should need no introduction. Famed for its buckling spring key mechanisms, the Model F is lusted over for its satisfying typing experience and Armageddon-proof build quality. First introduced in 1981, many of these keyboards will now naturally require basic maintenance. However, [Epictronics] recently went a step further and restored a Model F to like-new condition.

Missing keycaps were the least of his worries, as both new and old replacements are relatively easy to come by. [Epictronics] was more concerned about the forty-year-old foam sandwiched tight inside the keyboard, most likely having long since degraded. Apart from being plain gross, the decaying foam has the potential to foul the buckling spring switches. After taking apart the body and removing the ‘disgusting’ foam pad, a replacement was forged from neoprene and a handy-dandy hole punch.

Disassembly of the keyboard case required the gentle touch of a mallet, and reassembly needed similarly inappropriate tools. As demonstrated in this vintage clip from IBM, keyboard assembly was (and still is) performed automatically by robots, driven by an IBM Series/1 minicomputer. These robots were equally impressive for their precision and strength. Without access to IBM’s aptly named ‘closing tool’ and various other robotic helpers, [Epictronics] had to settle for pool noodles and a comically large clamp during reassembly, mixed with sheer determination.

Other neat tricks in the video include applying heat to reform the coiled keyboard cable, and using car polish to clean the case plastics. The latter has the potential to make things worse, so a delicate hand is needed to maintain the textured plastic.

We recently covered another Model F restoration, and it’s exciting to see so many dedicated hackers keeping these keyboards clickety-clacking well into the 21st century.

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Python Provides Classic Basic

October 8, 2021 by Al Williams 22 Comments

Back in the late 1970s and early 1980s when you turned on a PC, more often than not, you’d get a Basic prompt. Most people would then load a game from a tape, but if you were inclined to program you could just start writing. [Richpl] wanted that same experience and thus PyBasic was born. Along with some other Github contributors, the system has grown quite a bit and would be a good start at porting classic games or creating a replica vintage computer.

The interpreter lacks specialized hardware-specific features such as sound and graphics, of course, but then again, you could add them. It does have file I/O and also includes some interesting features like an analog of C’s ternary operator.

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