How To Cobble A Wobble Disk Roaster Together

March 14, 2021 by Kristina Panos 9 Comments

As with anything else, once your knowledge of coffee expands, the more attractive it becomes to control as much of the process as possible. Buying whole beans and grinding them at home is one thing, but you’re not a real coffee geek unless you’re buying big bags of green beans and roasting them yourself in small batches.

[Larry Cotton] has made an even more portable version of the wobble disk roaster we saw last summer. Beneath the housing made of aluminium flashing is the guts of a $15 Harbor Freight heat gun pointing upward at a metal strainer. A large metal disk mounted at a 45-degree angle to the spinning axis tosses and turns the beans as they get blasted with heat from below. [Larry] used a 12 VDC motor to run the wobble disk, and an an adapter to change the heat gun from 120 VAC to 12 VDC. This baby roasts 1½ cups of beans to city plus (medium) level in 12-15 minutes. Grab a cup of coffee and check it out after the break.

Roasting beans isn’t rocket science. Even so, there are some things you would benefit from knowing first, so here’s our own [Elliot Williams] on the subject of building DIY roasters.

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It’s Not A Computer If It Doesn’t Have A Cartridge Slot

March 13, 2021 by Jenny List 25 Comments

For viewers of sci-fi TV and films from the 1960s onwards, the miniaturisation of computer hardware has been something of a disappointment. Yes, it’s amazing that we can get 1.21 Jigabytes onto a memory card that fits comfortably under a postage stamp, but we were promised a different future. One of satisfyingly chunky data modules that activated everything from starships to handheld data recorders to malevolent rogue supercomputers, and one that has so far only materialised in the form of cartridges for game consoles.

Our colleague [Tom Nardi] has the solution for his cyberdeck though, in the form of 3D-printed cartridge shells that hide regular USB hardware and mate with a concealed USB socket in the slot. So far he’s designed cartridges for Flash drives, WiFi and Bluetooth adapters, a Wemos D1 Mini, a receptacle, and a parametric reference design.

It’s a bit of pleasing retro fun, but behind it all could be a surprisingly practical and useful expansion system. Each cartridge contains enough space for a lot of extra electronics, so it’s almost the ideal format for building a USB-driven project inside. Best of all since the interface is USB, it still works with conventional USB plugs and sockets. We like the idea, and it’s one that would be a good addition to any cyberdeck project.

We’re far more used to seeing home-made cartridges on game consoles.

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RIP Lou Ottens, Developer Of The Compact Cassette And More

March 12, 2021 by Jenny List 30 Comments

It’s with sadness that we note the passing at the age of 94 of the long-time Phillips engineer Lou Ottens, who is best known as the originator of the Compact Cassette audio tape format that was so ubiquitous through the later decades of the 20th century. Whether you remember cassettes as the format for 8-bit software, for teenage mixtapes on a Walkman, they began life at his hands in the early 1960s at the Phillips factory in Hasselt, Belgium.

Through a long career with the Dutch electronics company, he was responsible either directly or in part for a string of consumer electronic devices that we would see as ubiquitous over the latter half of the century. Before the cassette he had developed the company’s first portable reel-to-reel tape recorder, and in the 1970s while technical director of their audio division he led the team that would develop the CD. He was reported as saying that his great regret was not beating Sony to the development of the miniature cassette player that would be sold as the Walkman, but we’d suggest that the Walkman would not have been possible without the cassette in the first place.

So next time you handle a cassette tape, spare a thought for Lou, an audio engineer whose work permeated so much of the last half-century.

Thanks [Carl] for the tip.

Images: Lou Ottens by Jordi Huisman CC BY-SA 4.0 and “An early Phillips cassette recorder” by mib18 CC BY-SA 3.0

Framed PONG Is Picture Perfect

March 8, 2021 by Kristina Panos 9 Comments

How cool would it have been if arcade cabinets had acrylic panels all along that let you gaze upon the field of TTL chips within? When [Jürgen Müller] scored the innards of an original 1972 PONG machine, that’s exactly what the plan was: build a suitable cabinet that re-imagines PONG as a sleek and stunning work of art.

Instead of trying to cram a CRT in that nice mahogany cabinet, [Jürgen] opted to use an 8″ TFT screen. But get this: [Jürgen] built a Spartan 6 FPGA-based upscaler to adds the scan lines, blur, and afterglow that make it look like the classic PONG experience.

[Jürgen] also built an interface board that amplifies the sound, splits the video out into sync and brightness for the upscaler, and provides 5 V to the PONG circuit board. [Jürgen] decided to circumvent the board’s native voltage regulator in the name of keeping things cool.

[Jürgen] says the project’s web page is in a preliminary stage right now with more information to come. We sure hope that includes a video of it in action. For now, you can check out the files for the interface PCB, the FPGA board, and a list of the fonts.

Should you ever get tired of classic PONG, try playing it in one dimension.

Thanks for the tip, [Anonymous].

A Tiny Tube Amp For Not A Lot

March 7, 2021 by Jenny List 49 Comments

At the extreme budget end of tube audio lie single-tube amplifiers usually using very cheap small-signal pentodes. They’ve appeared here before in various guises, and a fitting addition to those previous projects comes from [Kris Slyka]. It’s a classic circuit with a transformer output, and it provides enough amplification to drive a pair of headphones or even a speaker at low levels.

The fairly conventional circuit of the tube amplifier.

Most tube enthusiasts will instantly recognize the anode follower circuit with a transformer in the anode feed through which the output is taken. The tube works in Class A, which means that it’s in its least efficient mode but the one with the least distortion. The transformer itself isn’t an audio part, but a small mains transformer taken from a scrap wall wart. It serves not only for isolation, but also to transform the high impedance output from the tube into a low impedance suitable for driving a headphone or speaker.

The HT voltage is a relatively low 24 V, but it still manages to drive headphones acceptably. Speaker levels require a pre-amp, but even then it’s likely that this circuit is pushing the tube beyond what it’s capable of with a speaker. The more it operates towards the edge of its performance envelope the more distortion it will generate and the worse a sound it will produce. This isn’t such a problem in a guitar application as here, but hi-fi enthusiasts may find it to be too much. It would be interesting to subject it as a headphone amplifier to a series of audio tests to evaluate the effect of a mains transformer over a dedicated audio one.

Last year we took a very in-depth look at the commonly-available Chinese kit pre-amps that use a similar anode-follower circuit but without the transformer. We’ve also seen a similar amp that uses an op-amp as an impedance converter, as well as a novel take on the idea whose unusual biasing allows it to run from only 3.3 volts. These circuits can be so cheap to get started with that we’d suggest anyone give them a try.

A Very Modern Tube Headphone Amplifier

February 27, 2021 by Jenny List 34 Comments

Once a discarded relic, over the years the humble vacuum tube has been rehabilitated in the arena of specialist audio. There are plenty of tube amplifiers now being manufactured, with a popular choice being headphone amplifiers that use a tube as a gain stage followed by an op-amp as a buffer with a low impedance output. This forms the basis of [Ratti3]’s amplifier, but with the added interest of a battery supply and a Bluetooth connection.

The tube circuit is a very conventional anode follower using an EF95 pentode. This provides plenty of gain and of course that “valve sound” beloved of audio enthusiasts, but suffers from an output impedance too high to drive a set of headphones. An NE5532 steps in for the op-amp buffer role, making for a very simple circuit. Power comes from a set of four 18650 Lithium-Ion cells with associated charger and balance boards, while a little switching boost converter provides the 100 volt HT for the tubes.

We’ve visited this type of amplifier before with a similar but much more rough-around-the-edges Chinese version. That had some astonishingly cheap Chinese tubes, but if we’re seeking better components it’s interesting to know just who makes tubes these days.

PS2 Gets Integrated HDMI

February 17, 2021 by Tom Nardi 35 Comments

It might be difficult to imagine in our modern HDMI Utopia, but there was a time when game consoles required proprietary cables to connect up to your TV. We’re not just talking about early machines like the NES either, turn of the millennium consoles like the PlayStation 2, Gamecube, and the original Xbox all had weirdo A/V ports on the back that were useless without the proper adapter.

But thanks to the efforts of [Taylor Burley], you can now upgrade your Slim PS2 with integrated HDMI capability. It’s not even a terribly difficult modification, as these things go. Sure there’s a lot of soldering involved to run from the console’s A/V connector to the commercially-made HDMI dongle he’s hidden inside the case, but at least it’s straightforward work.

Tapping into the console’s A/V connector.

As [Taylor] shows in the video after the break, all you have to do is remove the proprietary connector from the HDMI adapter dongle, and wire it directly into the console’s A/V port with a bit of ribbon cable. There are only 8 pins in the connector that you need to worry about, and the spacing is generous enough that there’s no problem getting in there with your iron and some standard jumper wires. You’ve also got to pull 5 V from the board to power the adapter, but that’s easy enough thanks to the system’s nearby USB ports.

There’s a perfect spot to mount the adapter board next to the console’s Ethernet connector, and once that’s tacked down with a bit of adhesive, the only thing left to do is cut a hole in the back of the enclosure for the HDMI port and snip away a bit of the metal RF shield. Presumably the same modification could be done on the original “fat” PS2, though you’ll be on your own for finding a suitable place to mount the board.

While modern game consoles can easily emulate their earlier peers, providing enhanced graphical fidelity and introducing modern conveniences like wireless controllers in the process, there’s still something to be said for playing classic games on the original hardware. Even if these projects are fueled by little more than youthful nostalgia, it’s a safe bet we’ll continue to see folks keeping these older machines running far into the future.

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