There’s a mystique among both audiophiles and musicians about vacuum technology, thus having a tube amp still carries a bit of a cachet. New ones can be bought for eye-watering prices and old ones can be had for the same price with the added frisson of unreliability. Happily it’s surprisingly straightforward to build your own, as [_electroidiot] shows us with a fairly inexpensive build.
The design is inspired by the guitar amps of the 1950s and 1960s so it’s not for audiophiles. The circuit is a pretty conventional single-ended one with a two stage double triode preamp and a single power output tube. The transformers are usually the difficult part of a build like this one, and here instead of resorting to using a mains transformer for audio they come from a defunct 1960s Phillips radio. We especially like the old-school construction technique with a folded aluminium chassis and liberal use of tag strips on which to build the circuits.
The result is something that would have been in no way out of place in the 1960s, and proves that tube circuitry isn’t beyond the constructor in 2023. If it’s whetted your appetite for more, we can help you there.
Once upon a time, laptops and other computer hardware often came with a fancy leather case for protection. That’s not really the case anymore, but it was in the golden era of the IBM ThinkPad. [polymatt] found a rare example, but wanted another one, so he decided to try and replicate it from scratch.
Leathercraft was a new discipline for [polymatt], and so the whole build was a learning experience. He started out by measuring the existing design and creating a diagram to guide his own work. He then traced the design on to a large piece of quality leather, carefully rounding the edges and adding a plastic stiffening plates to support the laptop where needed. Additional layers of leather were added to seal these in, and the leather was formed over guides to take the right shape. A slight misstep resulted in the case being too long, but a cut-and-shut job rectified the problem.
The finished result is a clean, impressive thing. Throughout the build, [polymatt] showed a certain mastery of the leatherworking tools that belied his lack of experience, too. The project should serve as a great inspiration to any other aspiring crafters who have contemplated creating their own custom leather goods for protecting their electronics. Video after the break.
If you try to sew leather on a standard consumer-grade machine, more often than not you’ll quickly learn its limits. Most machines are built for speed, and trying to get them to punch through heavy material at the low motor speeds often needed for leather work is a lesson in frustration.
How frustrating? Enough so that [Joseph Eoff] expended considerable effort to create this sewing machine speed controller for his nearly century-old Adler sewing machine. The machine was once powered by a foot treadle, which is probably why the project is dubbed “Bigfoot,” but now uses a 230 V universal motor. Such motors don’t deliver much torque when run at low speeds with the standard foot-pedal rheostat control, so [Joseph] worked up an Arduino-based controller with a tachometer for feedback and a high-power PWM driver for the motor.
There are a ton of details in [Joseph]’s post and even more in the original blog article, which is well worth a read, but a couple really stand out. The first is with the tachometer, which uses an off-the-shelf photointerrupter and slotted disc. [Joseph] was displeased with the sensor’s asymmetrical and unreliable output, so he made some modifications to the onboard comparator to square up the signal. Also interesting is the PID loop auto-tuning function he programmed into Bigfoot; press a button and the controller automatically ramps the motor speed up and down and stores the coefficients in memory. Nice!
The short video below shows Bigfoot in action with varying thicknesses of faux leather; there are also some clips in the original article that show the machine dealing with a triple thickness of leather at slow speed and not even breaking a sweat. Hats off to [Joseph] on a solid build that keeps a classic machine in the game. And if you want to get into the textile arts but don’t know where to start, we’ve got you covered.
When most people think of tube circuits, the first thing that comes to mind is often the use of high-voltage power supplies. It wasn’t a given for tube circuits, though, as a range of low-voltage devices were developed for applications such as car radios. It’s one of these, an ECH83 triode-heptode, which [mircemk] has taken as the basis of an audio preamplifier circuit.
The preamp circuit is pretty simple, being a two-stage single-ended design using both halves of the tube. Between the two is a three-band tone control circuit as used in classic guitar amplifiers, making for a serviceable and easily achievable way to chase that elusive “valve sound.”
There is much discussion among audio enthusiasts about the supposed benefits of vacuum technology as opposed to transistors in an amplifier. Much of it centres around the idea that tubes distort in the even harmonics while semiconductors are supposed to do so in the odd harmonics. Still, we’d be inclined to spot a bit of snake oil instead and point to early transistor amplifiers simply being not very good compared to the tube amps of the day. That said, a well-made tube amplifier set-up will sound just as amazing as it always did, and since this one is paired with a matching power amp we wouldn’t say no to it ourselves.
Instant photography was one of the twentieth century’s coolest-to-have consumer inventions, but when the digital photography revolution came it had few answers. It survives as a niche format thanks to Fuji’s Instax line and a group of Dutch entrepreneurs who revived a defunct Polaroid works, but what hasn’t made it are the earlier pack and roll film formats for which the picture is revealed by peeling apart a negative and positive side. All isn’t lost though, because a small Austrian company has been producing pack film cartridges as a handmade artisan product. To reduce the cost per print they’re now available as a DIY self-assembly kit, and it’s this which [In an Instant] is taking a look at in their latest video.
The kit has enough components for eight shots, and where the original cartridge would have held multiple exposures this one can only hold one at a time. The cartridge itself is cleverly formed from folded card as opposed to the plastic and metal of the original, and the components are a relatively straightforward assembly task. It’s a fascinating window into how the Polaroid pack film process worked, with the light-sensitive layer behind a pull-away black light screen, in front of the white positive sheet and with a pouch of developer chemicals to one side. It’s in no way cheap at somewhere about 10 dollars a shot, but it’s amazing that pack film can be recreated and for enthusiasts it’s a lifeline that keeps their cameras useful.
If you’ve ever been to the dental surgery and found yourself requiring some gum surgery, the chances are you’ll have found your dentist wielding an electronic probe to cauterise the flesh. It’s evidently some form of RF device because you are usually required to hold one of the electrodes while it’s being used, but annoyingly, for an engineer, it’s hardly the time or place to ask how it works. For the curious, then, [Keri Szafir] has the box of tricks behind the probe and is subjecting it to a teardown.
The box on her bench isn’t the one you’ll find in your dentist’s toolkit today, but its distant ancestor from the 1960s that integrates multiple functions into a single box. It’s a very period enclosure with typically 1960s-style vacuum tubes and point-to-point wiring. There’s an HF oscillator using a pair of EL81 power pentodes for that electrode you always wished you could ask your dentist about, and unexpectedly, a thyratron, a type of gas-filled switching tube not dissimilar to a thyristor, in a separate circuit for dental pulp testing. We’re not dental experts here at Hackaday, but [Keri] has done the research and explains the device in the video below the break. At one point, she observes that it’s quite a scary machine to be connected to a living person, and we can concur with that.
Her bench has provided a few projects here in the past, including one of her amplifiers. While it might be fun to tear down a more modern version, you are better off asking for old dental burrs.
Among Hackaday’s readership are likely to be many gadget enthusiasts who live for the latest electronics and who have obsessively followed gadget trends for most of their lives. You possess elite AliExpress-fu, and like the hipsters, you were into everything long before it was cool. It’s safe to say the Internet has revolutionized the world of the gadget freak, but in a time before even dial-up access there was another way into this most technophilic of pastimes. As soon as there was consumer electronics there were mail-order catalog companies slaking the thirst of the gadget-crazy, and [Cabel Sasser] is here with a look at both their heyday and their swansong.
Drew, just shut up and take my money!
He has a particular focus on the catalog produced during the 1980s by DAK Industries Inc, a North Hollywood California based company that was the work of an entrepreneur named Drew Kaplan. He presented a glittering array of the latest and greatest tech of the era, and packaged it with riveting descriptions and beautifully-shot glossy photographs. [Cabel] was hooked, and we would certainly have been too. There were digital watches with outrageous functionality, portable briefcase computers, novelty telephones, Hi-Fi components at knock-down prices, and plenty of cassette tapes to play in them.
Their signature was an engaging copy-writing style that really made you want the product, and here we enter an interesting story in itself. There was another mail order gadget company in the 1970s which used exactly the same formula but running full-page adverts, similar enough to be obviously connected in some way. Had DAK stolen the idea? Not quite, for these were the product of a man called Joseph Sugarman, who also ran a “Learn my formula for sales success” course. Drew Kaplan didn’t hesitate to attribute his success to the Sugarman course, leaving us with the surprising conclusion that there’s more to the “Learn my formula” business than simply making money from marks prepared to pay for the course.
