Convert A Cheap Tube Preamp Into A Headphone Amp With Jenny

February 27, 2025 by Lewin Day 21 Comments

Big-name tube amplifiers often don’t come cheap. Being the preserve of dedicated audiophiles, those delicate hi-fis put their glass components on show to tell you just how pricy they really ought to be. If you just want to dip your toe in the tube world, though, there’s a cheaper and more accessible way to get started. [Jenny List] shows us the way with her neat headphone amp build.

The build starts with an off-the-shelf preamp kit based around two common 6J1 tubes. These Chinese pentode valves come cheap and you can usually get yours hands on this kit for $10 or so. You can use the kit as-is if you just want a pre-amp, but it’s not suitable for headphone use out of the box due to its high-impedance output. That’s where [Jenny] steps in.

You can turn these kits into a pleasing headphone amp with the addition of a few choice components. As per the schematic on Github, a cheap transformer and a handful of passives will get it in the “good enough” range to work. The transformer isn’t perfect, and bass response is a compromise, but it’s a place to start your tinkering journey. Future work from [Jenny] will demonstrate using a MOSFET follower to achieve much the same result.

We’ve seen a great number of headphone amplifiers over the years, including one particularly attractive resin-encased example. Video after the break.

Continue reading “Convert A Cheap Tube Preamp Into A Headphone Amp With Jenny” →

A blue and white, 3D printed rose sits on a black surface with a fuzzy tan background behind it.

Thermorphs: Self-Folding 3D Prints

February 27, 2025 by Navarre Bartz 3 Comments

Prints separating from the build plate or warping when you don’t want them to is a headache for the additive manufacturer. [CNC Kitchen] walks us through a technique to use that warping to our advantage.

Based on a paper by researchers at the Morphing Matter Lab at UC Berkeley, [CNC Kitchen] wanted to try making 3D printed objects that could self-assemble when placed in hot water. Similar to a bimetal strip that you find in simple thermostats, the technique takes advantage of the stresses baked into the print and how they can relax when reaching the glass transition temperature of the polymer. By printing joints with PLA and TPU layers, you can guide the deformation in the direction you wish, and further tune the amount of stress in the part by changing the print speed of different sections.

[CNC Kitchen] found that Hilbert curve infill slows the printer down sufficiently to create relatively stress-free sections of a print to create flat sections which is an improvement over the original researchers’ all TPU flat sections with respect to rigidity. We’ve covered how to reduce warping in 3D prints, but now we can use those techniques in reverse to design self-assembling structures. These parts, being thermoplastic, can also be heated, reformed, and then exhibit shape memory when placed back into hot water. It’s very experimental, but we’re curious to see what sort of practical or artistic projects could be unlocked with this technique.

We’ve seen a few other interesting techniques with folded objects like laser cutter origami, some flat-to-folded 3D prints that might be interesting to try with this technique, and also folded hybrid mechanisms made with laser cutting and 3D printing.

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Esp-hal, A Stable-API ESP32 HAL Gift For Your Rust Code

February 27, 2025 by Arya Voronova 14 Comments

Looking to write Rust on the ESP32? You’re in luck, a new challenger has entered the scene, looking to help you write code that lasts – [Scott Mabin] and the team from Espressif have brought us the esp-hal 1.0.0-beta. From a personal project to an Espressif-sponsored one to an effort under Espressif’s wing, [Scott] tells us about the arduous journey of bringing first-class Rust support to ESP32 chips, Xtensa and RISC-V alike.

In particular, esp-hal, with the hal part standing for Hardware Abstraction Layer, focuses on providing you with a stable API to access hardware, making sure your code can remain stable for years to come. For now, you get drivers for GPIO, UART, SPI and I2C, as well as a number of auxiliary features like time and SoC reset, more than enough for a large amount of projects we hackers build with a generic MCU in mind.

Next stop? WiFi and BLE support, of course, an ESP32 just doesn’t feel the same without these two. Rust is a fun and seriously promising language, and it’s a joy to use! So, if you have a wireless-less project in mind and you’re looking for a HAL, try out the esp-hal, it might just be exactly what you need.

If you’re looking for examples, here’s an STM32 touchpad project with Rust firmware, a PIC32 Rust blinky demo, and we’ve even featured larger projects like this ESP32 open-source (reverse-engineered) WiFi MAC stack being written in Rust. In case you missed it, we’ve introduced Rust to you a couple of times, even as far as 2015!

Linux Fu: USB Everywhere

February 27, 2025 by Al Williams 20 Comments

It is a common problem: I have a USB device on a computer out in the shop, and I want to use it from the comfort of my office. What to do? Well, you could remote desktop into the distant machine. But, honestly, I always find any remote desktop more than ssh clunky and somewhat undesirable. Fortunately, Linux can do virtually anything if you only know how to do it. So, this time, I’ll show you how to transport a USB device over your network. Of course, I have a network that reaches out to the shop. It should be a simple matter to tell my desktop machine that one of its USB devices lives across the network. Well, it wasn’t that simple, but it is doable.

The Tools

The whole thing involves a program called usbip. That should be the end of it, but of course, it isn’t. In order for this to work, both machines on the network will need some kernel modules and a daemon on the server: the machine with the USB devices to share.

You may be able to install usbip from your package manager. On Ubuntu, it is in the linux-tools-common package, so a simple apt-get might give you everything you need. I wasn’t so lucky. Continue reading “Linux Fu: USB Everywhere” →

A man in a t-shirt and sport coat sits behind a table upon which are a small, black air fryer and a larger pale green model that looks more futuristic. Behind him is a black set of cube shelves (possibly IKEA Kallax) with different colored interiors lit and holding various bits of vintage technology equipment like landline phones and HiFi setups.

How Do Air Fryers Work?

February 27, 2025 by Navarre Bartz 63 Comments

Air fryers are the new hotness in the kitchen, but are they actually any different than a convection oven? [Technology Connections] walks us through the design of these countertop appliances to find out.

If you like your fries and chicken crispy instead of soggy, you traditionally had to eat out or spend the better part of an hour waiting on your food to cook to a crisp in the oven. Convection ovens significantly speed up this process by moving the air about and keeping the food from sucking most of the heat out of the stagnant layer just next to it.

It turns out that most air fryers are just a coil stove element and a fan placed above a basket which is just a fancy re-arrangement of the parts of a toaster or convection oven. The magic sauce here is the small size and the fact you don’t have to futz with pulling a hot wire basket out of your toaster or larger convection oven. The small size does give you a pretty big advantage in preheating and precise application of heat to the food for smaller batch sizes, but if you already have a convection oven, the advantages might not outweigh the additional space and cost of yet another kitchen gadget. We appreciate the sacrifice of eating “a lot of french fries” to test the differences between brands and conventional convection ovens for our edification.

If you’re looking for a way to make cookies faster instead of fries, how about this hack using a microwave and a heat gun? Or maybe it’s better to redesign the food instead of the appliance like this ramen in an edible package or these origami noodles.

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What Game Should Replace Doom As The Meme Port Of Choice?

February 27, 2025 by Lewin Day 113 Comments

DOOM. The first-person shooter was an instant hit upon its mrelease at the end of 1993. It was soon ported off the PC platform to a number of consoles with varying success. Fast forward a few years, and it became a meme. People were porting Doom to everything from thermostats to car stereos and even inside Microsoft Word itself.

The problem is that porting Doom has kind of jumped the shark at this point. Just about every modern microcontroller or piece of consumer electronics these days has enough grunt to run a simple faux-3D game engine from 1993. It’s been done very much to death at this point. The time has come for a new meme port!

Good Game

Doom became a popular meme port for multiple reasons. For one, it’s just complex and resource-intensive enough to present a challenge, without being so demanding as to make ports impractical or impossible. It’s also been open-source for decades, and the engine has been hacked to death. It’s probably one of the best understood game engines out there at this point. On top of that, everybody plays Doom at some point, and it was one of the biggest games of the 90s. Put all that together, and you’ve got the perfect meme port.

However, you can always have too much of a good thing. Just as The Simpsons got old after season 10 and Wonderwall is the worst song you could play at a party, Doom ports have been overdone. But what other options are there? Continue reading “What Game Should Replace Doom As The Meme Port Of Choice?” →

A Precisely Elegant Cyberdeck Handheld

February 27, 2025 by Donald Papp 15 Comments

[Nicholas LaBonte] shows off a Cyberdeck Handheld that demonstrates just how good something can look when care and attention goes into the design and fabrication. He wanted to make something that blended cyberpunk and nautical aesthetics with a compact and elegant design, and we think he absolutely succeeded.

On the inside is a Raspberry Pi and an RTL-SDR. The back of the unit is machined from hardwood, and sports a bronze heat sink for the Raspberry Pi. The front has a prominent red PSP joystick for mouse input and a custom keyboard. The keyboard is especially interesting. On the inside it’s a custom PCB with tactile switches and a ATmega32U4 running QMK firmware — a popular choice for DIY keyboards — and presents to the host as a regular USB HID device.

The keys are on a single plate of little tabs, one for each key, that sits between the front panel and press on the tact switches inside.

How did he make those slick-looking keys? It’s actually a single plate that sits between the front panel and the switches themselves. [Nicholas] used a sheet of polymer with a faux-aluminum look to it and machined it down, leaving metal-looking keys with engraved symbols as tabs in a single panel. It looks really good, although [Nicholas] already has some ideas about improving it.

On the right side is the power button and charging port, and astute readers may spot that the power button is where a double-stack of USB ports would normally be on a Raspberry Pi 5. [Nicholas] removed the physical connectors, saving some space and connecting the USB ports internally to the keyboard and SDR.

As mentioned, [Nicholas] is already full of ideas for improvements. The bronze heat sink isn’t as effective as he’d like, the SDR could use some extra shielding, and the sounds the keyboard ends up making could use some work. Believe it or not, there’s still room to spare inside the unit and he’d maybe like to figure out a way to add a camera, GPS receiver, or maybe a 4G modem. We can’t wait! Get a good look for yourself in the video, embedded below.

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