Full-Colour, Full-Motion Video – On An Audio Cassette!

A lot of projects we feature use video in some form or other, but that video is invariably digital, it exists as a stream of numbers in a computer memory or storage, and is often compressed. For some of us who grew up working with composite video there is a slight regret that we rarely get up-close and personal with an analogue stream, so [Kris Slyka]’s project putting  video on a conventional audio cassette is a rare opportunity. (Video, embedded below.)

It's fair to say this isn't the highest quality video.
It’s fair to say this isn’t the highest quality video.

Readers with long memories may recall the Fisher-Price PixelVision toy from the late 1980s which recorded black-and-white video on a conventional cassette running at many times normal speed. This system does not take that tack, instead it decreases resolution and frame rate to a point at which it can be recorded at conventional cassette speeds. The result is not particularly high quality, but with luminance on one side of a stereo recording and chrominance on the other it does work.

The video below the break is a run through the system, with an explanation of how video signals work. Meanwhile the code for both encoder and decoder are available through the magic of GitHub. If you’re interested further, take a look at our examination of a video waveform.

Continue reading “Full-Colour, Full-Motion Video – On An Audio Cassette!”

Gold Cables Really Do Work The Best

As a writer, I have long harboured a dream that one day an editor will buy me a top-of-the-range audio analyser, and I can set up an audio test lab and write pieces debunking the spurious claims made by audiophiles, HiFi journalists, and the high-end audio industry about the quality of their products. Does that amp really lend an incisive sibilance to the broader soundstage, and can we back that up with some measurable figures rather than purple prose?

An Audio Playground You Didn’t Know You Had

An Audio Precision APx525 audio analyser.
An Audio Precision APx525 audio analyser. Bradp723 (CC-BY-SA 3.0)

Sadly Hackaday is not an audio magazine, and if Mike bought me an Audio Precision he’d have to satisfy all the other writers’ test equipment desires too, and who knows where that would end! So there will be no Hackaday audio lab — for now. But that doesn’t mean I can’t play around with audio analysis.

Last month we carried a write-up of a Supercon talk from Kate Temkin and Michael Ossmann, in which they reminded us that we have a cracking general purpose DSP playground right under our noses; GNU Radio isn’t just for radio. Once I’d seen the talk my audio analysis horizons were opened up considerably. Maybe that audio analyser wouldn’t be mine, but I could do some of the same job with GNU Radio.

It’s important to stress at this point that anything I can do on my bench will not remotely approach the quality of a professional audio analyser. But even if I can’t measure infinitesimal differences between very high-end audio circuitry, I can still measure enough to tell a good audio product from a bad one.

Continue reading “Gold Cables Really Do Work The Best”

ESP8266 Adds Web Control To Old Home Theater

There was a time when you could hold onto a TV or A/V receiver for the better part of the decade and not feel as though you were missing out on the latest and greatest features. But today you’re lucky to get three years out of a “smart” TV before it’s either supplanted by a vastly improved version, or falls victim to some weird issue that (surprise, surprise) means you need to buy a new one.

A simple touch interface hosted on the ESP8266

Not content with the status quo of planned obsolescence, [aamarioneta] recently set out to add a sprinkling of modern convenience to a circa 2008 Denon AVR 2308 home theater receiver. Like any good A/V receiver, the AVR 2308 features a dizzying array of ports on the back panel, one of which happens to be for an external infrared receiver. This turned out to be the perfect place to jack in an ESP8266, earning this 12 year old receiver an honorary membership into the Internet of Things.

The interesting thing about this hack is that there’s actually no IR involved. Sure, the code could be used to drive an IR LED attached to the ESP8266’s GPIO pins, and the AVR 2308 would respond as if the original remote was being used; but where’s the fun in that? Thanks to the receiver port, they’re able to inject the IR codes directly into the device. It’s the same protocol, just without the photons.

With a simple web-interface running on the ESP8266, they can control the AVR 2308 from a smartphone’s browser anywhere in the house. From here it would only take a few more lines of code to tie it into an existing home automation system or add in support for Alexa voice control.

We love seeing projects that add modern features to older hardware, as that’s one less piece of gear sent to an early grave because its owner felt they were behind the curve. It’s getting a bit unfriendly out there for consumers, and anything that puts the power back into the owner’s hands is a step in the right direction.

Make A Set Of Headphones From Scratch

There are a variety of ways to enjoy your audio, of which headphones are one. Making a set of headphones is a straightforward enough project, but [madaeon] has taken the art to a new level by building the headphone drivers from scratch rather than using an off-the-shelf pair.

The result is a set of moving coil drivers with a construction technique involving using the semi-opaque thin window from an envelope as a diaphragm and as a former for the coil. Cyanoacrylate adhesive holds everything in place. The diaphragm is suspended across the mouth of a cardboard tube with the coil positioned above a magnet, resulting in the minimum moving mass necessary for as good a sound reproduction as possible. Judge for yourself, there’s a video that we’ve placed below the break.

The drivers are placed in a set of 3D-printed on-ear holders, and while they probably won’t match an expensive set of commercial headphones, we’d hazard a guess that they won’t have too bad quality. At the very least, it’s an interesting design to base further experimentation on.

Surprisingly few home made speaker or headphone drivers have made it onto these pages, probably because of the ubiquity of the ready-made article. An exception is this flexible PCB speaker, and of course we’ve also talked about home made electrostatic speakers. Continue reading “Make A Set Of Headphones From Scratch”

The Red Dwarf Talkie Toaster Made Real

It’s cold outside, there’s no kind of atmosphere, you’re all alone, more or less. More or less meaning that you share the gigantic mining ship that is your home on the other side of the galaxy with an ineffectual android, a humanoid descended from your cat, a holographic representation of your dead colleague who’s a complete smeghead, and a really annoying sentient toaster that’s obsessed with bread products. If all this rings a bell, then maybe you’re familiar with the cult BBC TV series, Red Dwarf.  It’s a show that evidently [Bill Dudley] has spent too much time watching, because he’s created a really convincing replica of that talking toaster.

The base toaster is a toy appliance with a little clockwork ejector for toy toast, that comes with plenty of space inside and is easy to accessories for the classic Talkie Toaster look. Inside is an off-the-shelf MP3 player board and a home-made PCB which drives a set of LEDs behind the speaker grille in time with the audio. The result won’t make any toast, waffles, or even crumpets, but it will delight any Red Dwarf fans who might be passing, whether someone has smoked them a kipper or not.

Surprisingly this is not the first Talkie Toaster build we’ve seen. If they met, would they have a harmonious conversation about bagels?

Sniffing Signals To Teach Old Speakers New Tricks

Like many of the stories you’ll find on these pages, this one starts with a user being annoyed about their device’s inability to perform a simple task. All [Jay Tavares] wanted was for his Bose Cinemate speakers to turn themselves on and off as needed. It seems like a reasonable enough request, and indeed, is exactly the point of HDMI’s Consumer Electronic Control (CEC) feature. But in this case, it would take a bit of custom hardware to get similar functionality.

Unfortunately, the speakers [Jay] has only support optical audio; so any interoperability with HDMI-CEC (hacked or otherwise) was immediately out the window. Still, he reasoned that he should be able to detect when the TOSLINK audio source is actually active or not, and give the speaker system the appropriate signal to either power on or shut down. You might think this would require some kind of separate stand-alone device, but as it turns out, all the necessary information was available by reverse engineering the connection between the receiver and the subwoofer.

After some investigation, [Jay] found that not only was the content of the TOSLINK audio source being sent over this DB9 cable, but so were the control signals required to turn the system on and off. So he designed a simple pass-through device with an ATtiny85 and a couple passives that latches onto the relevant lines in the cable.

When audio is detected over the optical connection, the MCU will inject the appropriate signals on the control line to simulate the user pressing the “Power” button the remote. When the chip hasn’t detected audio after 10 seconds, it sends the signal to shut the speakers off.

While [Jay] notes he can’t guarantee this works on anything other than the particular Bose Cinemate GS Series II system he has, we’d be willing to bet the concept could be adapted to other models or even brands that use a similar cable to link their principle components. If all else fails, you could always add an ESP8266 to your sound system and control it over WiFi.

THAT Preamp

It is easy to cobble together projects these days. ICs make it simple and microcontrollers even easier. However, we always respect a project that really goes from concept to finished product and that’s what we liked about [Curt Yengst’s] “THAT” Thing microphone preamp.

In part 1 of his post about it, he talks about the basic ideas including the chips from THAT — a small but high-end audio chipmaker — he uses. The first chip is a low-noise audio preamp and the other is a balanced line driver.

In part 2, we get to see [Curt] go from breadboard testing to PCB fabrication all the way to the finished rack-mounted device with a good looking front panel. It worked, but like all designers, [Curt] was already thinking about the next version.

Continue reading “THAT Preamp”