A Tube Stereo Amplifier, From Scratch

November 20, 2024 by Jenny List 1 Comment

A conventional tube amplifier has a circuit whose fundamentals were well in place around a hundred years ago, so there are few surprises to be found in building one today. Nevertheless, building one is still a challenge, as [Mike Freda shows us with a stereo amplifier in the video below the break.

The tubes in question are the 12AU7 double triode and 6L6 tetrode, in this case brand new PSVANE parts from China. The design is a very conventional single-ended class A circuit, with both side of the double triode being used for extra gain driving the tetrode. The output uses a tapped transformer with the tap going to the other grid in the tertode, something we dimly remember as being an “ultra-linear” circuit.

There’s an element of workshop entertainment in the video, but aside from that we think it’s the process of characterising the amp and getting its voltages right which is the take-away here. It’s not something many of us do these days, so despite the apparent simplicity of the circuit it’s worth a look.

These modern tubes come from a variety of different sources, we’ve attempted to track them down in the past.

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The Barcode Beast Likes Your CDs

November 19, 2024 by Jenny List 42 Comments

Over the years we’ve featured many projects which attempt to replicate the feel of physical media when playing music. Usually this involves some kind of token representation of the media, but here’s [Bas] with a different twist (Dutch language, Google Translate link). He’s using the CDs themselves in their cases, identifying them by their barcodes.

At its heart is a Raspberry Pi Pico W and a barcode scanner — after reading the barcode, the Pi calls Discogs to find the tracks, and then uses the Spotify API to find the appropriate links. From there, Home Assistant forwards them along to a smart speaker for playback. As a nice touch, [Bas] designed a 3D printed holder for the electronics which makes the whole thing a bit neater to use.

We this approach for its relative simplicity, and because the real CDs ad the retro touch it’s a real winner. You can find all the resources in a GitHub repository, should you wish to make your own. Meanwhile, it’s certainly not the first barcode scanner we’ve seen.

BASIC Co-Inventor Thomas Kurtz Has Passed Away

November 15, 2024 by Jenny List 71 Comments

It’s with sadness that we note the passing of Thomas E. Kurtz, on November 12th. He was co-inventor of the BASIC programming language back in the 1960s, and though his creation may not receive the attention in 2024 that it would have done in 1984, the legacy of his work lives on in the generation of technologists who gained their first taste of computer programming through it.

A BBC Micro BASIC program that writes "HELLO HACKADAY!" to the screen multiple times. — For the 1980s kids who got beyond this coding masterpiece, BASIC launched many a technology career.

The origins of BASIC lie in the Dartmouth Timesharing System, like similar timesharing operating systems of the day, designed to allow the resources of a single computer to be shared across many terminals. In this case the computer was at Dartmouth College, and BASIC was designed to be a language with which software could be written by average students who perhaps didn’t have a computing background. In the decade that followed it proved ideal for the new microcomputers, and few were the home computers of the era which didn’t boot into some form of BASIC interpreter. Kurtz continued his work as a distinguished academic and educator until his retirement in 1993, but throughout he remained as the guiding hand of the language.

Should you ask a computer scientist their views on BASIC, you’ll undoubtedly hear about its shortcomings, and no doubt mention will be made of the GOTO statement and how it makes larger projects very difficult to write. This is all true, but at the same time it misses the point of it being a readily understandable language for first-time users of machines with very little in the way of resources. It was the perfect programming start for a 1970s or 1980s beginner, and once its limitations had been reached it provided the impetus for a move to higher things. We’ve not written a serious BASIC program in over three decades, but we’re indebted to Thomas Kurtz and his collaborator for what they gave us.

Thanks [Stephen Walters] for the tip.

I Want To Believe: How To Make Technology Value Judgements

November 15, 2024 by Jenny List 68 Comments

In the iconic 1990s TV series The X Files, David Duchovny’s FBI agent-paranormal investigator Fox Mulder has a poster on his office wall. It shows a flying saucer in flight, with the slogan “I Want To Believe”. It perfectly sums up the dilemma the character faces. And while I’m guessing that only a few Hackaday readers have gone down the full lizard-people rabbit hole, wanting to believe is probably something that a lot of us who love sci-fi understand. It would be a fascinating event for science if a real extraterrestrial craft would show up, so of course we want to believe to some extent, even if we’re not seriously expecting it to appear in a Midwestern cornfield and break out the probes any time soon.

By All Means Believe. But Don’t Wreck Your Career

The first page of a scientific paper: "Electrochemically induced nuclear fusion of deuterium". — The infamous Fleischmann and Pons paper from 1989 on cold fusion.

Outside the realm of TV drama and science fiction it’s a sentiment that also applies in more credible situations. Back at the end of the 1980s for example when so-called cold fusion became a global story it seemed as though we might be on the verge of the Holy Grail of clean energy breakthroughs. Sadly we never got our Mr. Fusion to power our DeLorean, and the scientific proof was revealed to be on very weak foundations. The careers of the two researchers involved were irreparably damaged, and the entire field became a byword for junk science. A more recently story in a similar vein is the EM drive, a theoretical reactionless force generator that was promising enough at one point that even NASA performed some research on it. Sadly there were no magic engines forthcoming, so while it was worth reporting on the initial excitement, we’re guessing the story won’t come back.

When evaluating a scientific or technical breakthrough that seems as miraculous as it is unexpected then, of course we all want to believe. We evaluate based on the information we have in front of us though, and we all have a credibility pyramid. There’s nothing wrong with having an interest in fields that are more hope than delivery, indeed almost every technology that powers our world will at some time have to overcome skepticism in its gestation period. Perhaps it’s best to say that it’s okay to have hope, but hope shouldn’t override our scrutiny of the proof. Of course I want a perpetual motion machine, who wouldn’t, but as a fictional engineer once allegedly said, “Ye cannae change the laws of physics”. Continue reading “I Want To Believe: How To Make Technology Value Judgements” →

Nebraskan Farmers Were Using Wind Turbines Before Environmentalism Was Invented

November 14, 2024 by Jenny List 18 Comments

To a casual observer of public discourse here in 2024 it seem extremely odd that the issue of replacing coal fired power stations with wind turbines is a matter of controversy, whether in America or Europe it’s an issue which causes some sparks to fly. The Atlantic has a recent article with a set of pictures from a gentler time in which the industrious nature of Nebraskan farmers in the 1890s receives praise as they create a wide variety of home-made wind turbines.

Farmers have always been the best hardware hackers, using what they have at hand to solve their problems and create the things they need. Perhaps out image of agricultural wind power is one of commercially produced wind pumps, but these are the generation of home-made devices which preceded that. Some of them look conventional to modern eyes, but others such as the horizontal “Jumbo” turbines have little equivalent today.

It’s easy to forget with so many energy sources at our disposal, that in the past the locality affected the choice of motive power. The Netherlands doesn’t have windmills because they are pretty, but because hundreds of years ago they lacked handy coal mines or convenient heads of water. Similarly out in the Nebraskan prairies they had plenty of wind, and never the folk to pass up on an opportunity, they made the best of it. And we’re very glad over a century later, that someone took the time to record their work.

If you’re hungry for more old-style wind power, we’ve got you covered, meanwhile 19th century America was no stranger to clever ways to use power.

Thanks [Hugh Brown] for the tip.

A Vintage Radiator Core, From Scratch

November 13, 2024 by Jenny List 25 Comments

There are sadly few 1914 Dennis fire engines still on the road, so when the one owned by Imperial College in London needs a spare part, it can not be ordered from the motor factors and must be made from scratch. Happily, [Andy Pugh] is an alumnus with the required metalworking skills, so in the video below we see him tackling the manufacture of flattened brass tubes for its radiator core.

Forming a round tube to a particular shape is done by pulling it through a die whose profile gradually changes from round to the desired shape. We see him make a couple of tries at this, finally succeeding with one carefully designed to have a constant circumference. The use of CNC machining is something that wouldn’t have been available in the Dennis works in the early 20th century, so we can marvel at the skills of the machinists back then who made the original. Here in 2024 he makes a drawing rig with a geared chain drive suitable for larger scale production.

The video is both a fascinating look at tube drawing and a mind-cleansing piece of workshop observation, and we have to say we enjoyed watching it. If [Andy]’s name sounds familiar to you, this might be because this isn’t the first go he’s had at manufacturing vehicle parts.

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All Aboard The Good Ship Benchy

November 9, 2024 by Jenny List 26 Comments

We’ll go out on a limb here and say that a large portion of Hackaday readers are also boat-builders. That’s a bold statement, but as the term applies to anyone who has built a boat, we’d argue that it encompasses anyone who’s run off a Benchy, the popular 3D printer test model. Among all you newfound mariners, certainly a significant number must have looked at their Benchy and wondered what a full-sized one would be like. Those daydreams of being captain of your ship may not have been realized, but [Dr. D-Flo] has made them a reality for himself with what he claims is the world’s largest Benchy. It floats, and carries him down the waterways of Tennessee in style!

The video below is long but has all the details. The three sections of the boat were printed in PETG on a printer with a one cubic meter build volume, and a few liberties had to be taken with the design to ensure it can be used as a real boat. The infill gaps are filled with expanding foam to provide extra buoyancy, and an aluminium plate is attached to the bottom for strength. The keel meanwhile is a 3D printed sectional mold filled with concrete. The cabin is printed in PETG again, and with the addition of controls and a solar powered trolling motor, the vessel is ready to go. Let’s face it, we all want a try!

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