Know Audio: Amplifiers And Distortion

July 29, 2021 by 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” →

3D Printer Add On Makes Sharp(ie) Colors

July 29, 2021 by 19 Comments

We’ve all seen 3D printed jigs that use a permanent marker to color filament as it goes into the hot end. [Sakati84] has a completely different idea. A holder on the print head can pick up one of several pens and use it to color the layer the hot end just laid down. In the video below, it looks like it works well and, although we imagine it will be a bear to calibrate on height, it seems like something you could replicate with nearly any conventional printer.

Logically, you print a layer with no pen in the holder and when you do pick up a pen, it will need to be somewhat lower than the print nozzle or else you’ll drag around in the fresh plastic.

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Orbiter Is Now Open Source

July 29, 2021 by 30 Comments

We always have it on our list to learn more about Orbiter. If you haven’t seen it, it is a hyperrealistic space simulator. Granted, you can put it in an easy mode, but its real strength is you can very accurately model spacecraft like the Space Shuttle and have very realistic controls. In order to spur development, the program is now open source.

We think this is interesting for two reasons. First, if you ever wanted to contribute into a project of this scope, here’s your chance. You might not want to write a full-blow space simulator but you might have something to add. However, open source also means you can see how the program works and either reuse it in your own open source projects or just simply learn from the techniques.

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Tabletop Basketball With Tentacles

July 28, 2021 by 4 Comments

Unlike football/soccer and foosball, basketball doesn’t really lend itself to being turned into a tabletop game quite that easily. [The Q] has found a way around that, employing tentacle mechanisms to create a two-player, basketball-like game.

Each player uses a pair of two-axis control sticks and a foot pedal to operate a cable-driven tentacle with a gripper on the end. These are two stage tentacles, meaning that the top and bottom halves are independently controlled. The tentacles consist of a series of laminated foam discs clued onto bicycle cable sleeves. The cables are open in the section they control, and operate in a push-pull arrangement. The spring-loaded grippers are operated by the foot pedals, with a single cable running down the center of the tentacle.

The game looks quite fun and challenging, and we can imagine it being even more entertaining with teams of two or three people operating each tentacle. Add a bit of alcohol to adult players, and it might become downright hilarious, although the mechanisms would need to be beefed up a bit to survive that level of punishment.

We suspect [The Q] read [Joshua Vasquez]’s incredibly detailed three-part guide on two-stage tentacle mechanisms. Combine that with his guide to cable mechanism math, and you’d be well-equipped to build your own. Continue reading “Tabletop Basketball With Tentacles” →

Liquid Nitrogen Isn’t Suitable For Steam Engines

July 28, 2021 by 28 Comments

Liquid nitrogen is fun stuff to play with, as long as you’re careful and avoid freezing your own fingers off and shattering them on the workbench. As the liquid turns to gaseous nitrogen at around -196 C, [The Action Lab] figured that it could be used to propel a simple steam engine at room temperature. Testing this out had amusing results.

The device under test is a Hero’s Engine, otherwise known as an aeolipile. This consists of a hollow sphere filled with water, fitted with a series of nozzles that shoot out steam when the vessel is heated. Via the rocket principle, this causes the device to rotate about its axis.

When filled with water and heated with a candle, the aeolipile spun at up to 2520 RPM. [The Action Lab] next tested it filled with water in a vacuum chamber, with the low pressure causing the water to boil at room temperature. The effect was less impressive however, with the engine spinning at a much slower rate.

The best result was with liquid nitrogen inside the engine. With the nitrogen quickly boiling at room temperature, the aeolipile quickly spun up to a great speed. The engine stand had to be steadied to avoid it tipping over, before the seal at the top of the engine blew off from overpressure.

We’d love to see the same experiment done with a piston-type steam engine, too. Video after the break.

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Video Feedback Effects Make A Glorious Spectacle In HD

July 28, 2021 by 27 Comments

Video feedback is perhaps best known for its appearance in the film clip to Bohemian Rhapsody. It’s not a particularly popular effect that you see too often, as it’s rather messy to set up what with cameras filming screens and what not. Regardless, the effects possible are glorious, as demonstrated by [Dave Blair] and his amazing video feedback kinetic sculpture.

No computer is involved at all in the process – it’s just classic, old school video feedback. It’s produced by pointing a camera at a screen and feeding the image back to that same screen. Three cameras are combined with twin video switchers and a beam-splitting pane of glass, along with a source image via an HDMI input.

By turning and spinning the various cameras, [Dave] is able to generate beautiful curving fractal-like effects using the source imagery, with a rainbow of color melting and warping together as he interacts with the sculpture. It’s a beautiful effect and something we’re surprised we don’t see more of in the video industry.

Hopefully [Dave] is enlisted to put his machine to work on the next [Doja Cat] film clip so we can get more of this goodness. Video after the break.

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Scanning Medium Format Film On A 35mm Scanner

July 28, 2021 by 6 Comments

Scanning film is great for archival purposes as well as sharing said photos digitally. However, if you’re scanning 120 film, aka medium format, it can be expensive to get the requisite hardware. 35mm scanners are comparatively more common, so [Christian Chapman] decided to modify one to suit medium film instead.

The hack is for the Plustek 8100, and requires modifying the scanner in two ways. Firstly, the driver has to be scanned to sweep a longer range to take into account the bigger film. Secondly, a part of the film carriage has to be replaced so it doesn’t show up in the scanners field of view.

The former is achieved by using the sane-genesys scanner software backend, which can be easily modified to adjust the scan length values appropriately. The latter is achieved via 3D printing replacement components that fit without blocking the requisite area.

It’s a tidy hack and one that allows [Christian] to both scan medium format film as well as overscan 35mm film to capture details from the sprocket hole area. We’ve seen fully custom film scanner builds before, too. If you’ve built your own scanner, be sure to drop us a line!