Know Audio: Amplifiers And Distortion

July 29, 2021 by Jenny List 31 Comments

As we’ve traced our no-nonsense path through the world of Hi-Fi audio, we’ve started with the listener, understood the limitations of the human ear, and thence proceeded to the loudspeaker. We’ve learned a bit about speaker cabinets and their design, so it’s time to venture further down the chain to the amplifier that drives those speakers.

The sharp-eyed will be ready to point out that along this path also lies the speaker cables, but since we’ll be looking at interconnects at a later date we’ll be making the dubious and simplistic assumption for now that the wires between speaker and amplifier are ideal conductors that don’t have a bearing on listening quality. We’ll be looking at amplifiers in enough detail to warrant more than one piece on the subject, so today we’ll start by considering in a slightly abstract way what an amplifier does and where it can fall short in its task. We’ll be introducing probably the most important thing to consider in any audio system, namely distortion.

The job of an audio amplifier is to take an audio signal at its input and present the same signal on its output at a greater amplitude. In the case of a preamplifier it will usually be designed to work with high impedances in the order of 50 kΩ at both input and output, while in a power amplifier designed to drive speakers or headphones it will drive a much lower impedance. Commonly this will be 4 Ω or 8 Ω for loudspeakers, and 32 Ω for headphones. Continue reading “Know Audio: Amplifiers And Distortion” →

Swamp Gas Will Get You Home

July 28, 2021 by Jenny List 61 Comments

The energy to power a motorcycle has to come from somewhere, be it a power station, a solar panel, a gas station, or a hydrogen plant. There have been many ways to reduce the cost of extracting that energy over the years, but we think [Gijs Schalkx] may have hit upon one of the cheapest and simplest we’ve ever seen. It may not be free gas, but it is free swamp gas! His Uitsloot (we think that’s Dutch for “From the ditch”) motorcycle gets its power from methane generated in the sediment at the bottom of the Netherlands’ many waterways.

At its heart is a venerable Honda Cub moped, we’re guessing of the 50 cc version. On its pillion is a large clear container, inside of which is a balloon filled with gas. He doesn’t go into details in the video below the break, but we’re guessing he’s injecting the gas into the Honda’s airbox from which the engine can suck the gas/air mixture. We like his gas collector, a large inner tube with a collector funnel in its centre that floats on the water. He dons some waders and pokes the sediment with a long stick to release bubbles of methane. He then uses a long hose and a bicycle pump to inflate the balloon with the collected gas. We see him zipping around the streets of Arnhem under this unconventional power, though sadly we don’t see how far a full balloon will take him.

There’s a discussion to be had as to the environmental credentials of this project, but we think given that the naturally generated methane which would find its way into the atmosphere eventually has a greater effect on the climate than the CO2 produced by the engine, he may be onto a winner. It is however not a system that would scale to more than a few drivers poking at bogs with a stick.

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It Takes A Lot To Build A Hacker’s Laptop

July 28, 2021 by Jenny List 80 Comments

An essential tool that nearly all of us will have is our laptop. For hardware and software people alike it’s our workplace, entertainment device, window on the world, and so much more. The relationship between hacker and laptop is one that lasts through thick and thin, so choosing a new one is an important task. Will it be a dependable second-hand ThinkPad, the latest object of desire from Apple, or whatever cast-off could be scrounged and given a GNU/Linux distro? On paper all laptops deliver substantially the same mix of performance and portability, but in reality there are so many variables that separate a star from a complete dog. Into this mix comes a newcomer that we’ve had an eye on for a while, the Framework. It’s a laptop that looks just like so many others on the market and comes with all the specs at a price you’d expect from any decent laptop, but it has a few tricks up its sleeve that make it worth a glance.

These USB-C based modules are a neat idea.

Probably the most obvious among them is that as well as the off-the-shelf models, it can be bought as a customised kit for self-assembly. Bring your own networking, memory, or storage, and configure your new laptop in a much more personal way than the norm from the big manufacturers. We like that all the parts are QR coded with a URL that delivers full information on them, but we’re surprised that for a laptop with this as its USP there’s no preinstalled open source OS as an option. Few readers will find installing a GNU/Linux distro a problem, but it’s an obvious hole in the line-up.

On the rear is the laptop’s other party trick, a system of expansion cards that are dockable modules with a USB-C interface. So far they provide USB, display, and storage interfaces with more to come including an Arduino module, and we like this idea a lot.

It’s all very well to exclaim at a few features and party tricks, but the qualities that define a hacker’s laptop are only earned through use. Does it have a keyboard that will last forever, can it survive being dropped, and will its electronics prove to be fragile, are all questions that can be answered only by word-of-mouth from users. It’s easy for a manufacturer to get those wrong — the temperamental and fragile Dell this is being typed on is a case in point — but if they survive the trials presented by their early adopters and match up to the competition they could be on to a winner.

Classroom Surplus Becomes Linux Powerhouse

July 27, 2021 by Jenny List 30 Comments

The SMART Response XE is a handheld computer that was originally sold for use in the classroom as a terminal for pupils taking tests. It’s now cheap enough on the surplus market to have become a target for experimenters, and we’ve seen them with a variety of cool hacks. We particularly like what [chmod775] has done with it, putting a VT100 terminal emulator on the device and hiding a NanoPi Neo Air single board computer in the battery bay. Powered from a USB battery bank, it gives a fully-featured Linux terminal in the palm of the hand. We see it running an Ubuntu LTS version, and it’s clear that it’s a functional and usable device.

This raises a more abstract question though: We’d guess comparatively few of us write software through an old-style dumb terminal, instead we’re more likely to get our terminal experience at a much more accomplished command line with all the conveniences of a modern desktop surrounding it. How many of us could comfortably return to the limited confines of a VT100 emulator on an odd-sized LCD display? We’d be interested to hear [chmod755]’s experiences using it, because if it retains usability it’s a device we wouldn’t mind having ourselves.

Hungry for more SMART Response XE hacks? Take a look at the BASIC computer, or the spectrum analyser.

If Society Is In Danger Of Collapse, Here’s How We Should Do Our Bit

July 26, 2021 by Jenny List 107 Comments

If you’ve been following the news, you can’t have missed the series of floods, droughts, and wildfires that have occurred seemingly in all corners of the world. Coming on the heels of a Northern Hemisphere winter that had its own extreme weather events, it would be perhaps foolhardy not to by now take climate change seriously. You may also have seen the news about a return to a 1970s paper in which MIT crystal-ball-gazers predicted the collapse of our civilisation in the mid-21st century, and a review based upon the empirical data gathered since then which concluded that we could be right on track with that prediction set to happen in about 2040.

It’s sobering stuff, and something which could so easily form the basis of many a Hollywood apocalyptic disaster movie. But sitting here in 2021 amid extreme weather events and a global pandemic it’s certainly something to think about. It’s not as though we’re riding biogas-powered weapon cars through the post-apocalyptic desert just yet though, we still have a chance to do something to avert catastrophe and no doubt over the next decade a raft of changes will reduce our CO2 impact and make our infrastructure more resilient to stave off any coming crises.

Our mind was turned to the halcyon time before the pandemic, to the Danish BornHack hacker camp back in August 2019. One of the talks at the event came from [Igor Nicolic], whose day job as an academic with Delft University of Technology takes him into the study of ecology and sustainability. In it he looks at the current state of global sustainability, and identifies the roles which the hardware hacker community could play in an uncertain future. It’s a fascinating lecture from an expert in the field and it’s well worth a watch and taking note of his points, so we’ve placed it below the break. Continue reading “If Society Is In Danger Of Collapse, Here’s How We Should Do Our Bit” →

Are Hackers Being Let Down In Education?

July 23, 2021 by Jenny List 62 Comments

In my work for Hackaday over the years I have been privileged to interact with some of the most creative people I have ever met, I have travelled far more than I ever did when I toiled unseen in an office in Oxford, and I have been lucky enough to hang out in our community’s spaces, camps, and dives across Europe.

Among the huge diversity of skills and ideas though, it’s striking how many of us share similar experiences and histories that have caused us to find our people in rooms full of tools and 3D printers. One of these things I found surprising because I thought I was the only one; I never fit in with the other kids at school, I found much of the teaching incomprehensible and had to figure things out for myself. As an exercise recently I did a straw poll among some of my friends, and found that a significant majority had a similar experience. Clearly something must have gone badly wrong in the way we were being taught that so many of us could have been let down by our schooling, and maybe to understand the needs of our community it’s time to understand why.

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Retrotechtacular: Nuvistor, Vacuum’s Last Gasp

July 21, 2021 by Jenny List 51 Comments

In 2021 all our electronics are solid state, in that they exclusively use semiconductor devices as their active components. Some of us may experiment with vacuum tubes, but only for curiosity or aesthetic purposes. Semiconductors have overtaken vacuum devices in all but the rarest of niche applications due to their easier design requirements, greater reliability, lower cost, and increased performance.

It was not always this way though, and there was a period at the start of the semiconductor era when transistors and vacuum tubes existed together side-by-side and competed directly. Vacuum tube manufacturers continued to create new devices into the 1970s, and in doing so they pushed the boundaries of their art in unprecedented directions. [David W Knight] has a page dedicated to the Nuvistor, something his calls the “final evolution of the thermionic valve”. His comparison photo seen above shows a Nuvistor on the left — a miniature vacuum tube you’ve likely never seen before.

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