home entertainment hacks

752 Articles

Prison TV Gets Simple Speaker Mod

April 13, 2023 by 20 Comments

American prisons are strict about television use. Typically they’re only to be used with headphones, and their enclosures need to be transparent so they can’t be used to smuggle goods. ClearTech makes TVs that meet these specifications, and when [Steve Pietras] got his hands on just such a unit, he set about modding it for use in the free world.

Getting into the TV isn’t easy; ClearTech built the units using special security fasteners unlike any we’ve seen before. [Steve] found a way to deal with these, though declines to share his technique in his video. Once inside though, his task is relatively straightforward. He steps through where to install speakers in the TV’s housing, and how to hook them up to the right spots on the main circuit board. With the case closed back up, [Steve] is able to use the TV without headphones, and without the threat of getting shanked by a fellow inmate who really doesn’t want to hear Jeopardy while they’re trying to read.

It’s not every day we get to look at a piece of obscure hardware like this. We’d never seen a prison TV before, and now we feel like experts on the topic. Of course, we’re no strangers to esoterica at Hackaday.

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No Home Cinema Is Complete Without A Motorized Projector

April 5, 2023 by 5 Comments

In the home of the future, everything is automated. Some of us are already there, in dwellings fully tricked-out with IoT and smart home devices. But they don’t somehow look as futuristic as a home in which everything is motorized. We don’t know whether this was the intention, but we certainly get a futuristic vibe from [Sam Baker]’s home cinema projector mount. It’s no mere bracket, instead on command the projector descends from concealment in the ceiling on a custom scissor lift mechanism.

A scissor lift is a simple enough mechanism, but since he was 3D printing one that had to withstand the weight of the projector, it took him a while to get it right. Even the lead screw which drives it is also printed, turned by a stepper motor. As the brains of the unit needn’t be particularly accomplished, an Arduino Nano does the job well enough.

It’s fair to say that his projector isn’t the heaviest of models, but the result glides smoothly down from the ceiling for a perfect home cinema experience. We like it.

It’s Difficult To Read An Audiophile Guide As An Analogue Engineer

March 28, 2023 by 138 Comments

Sitting on a train leaving the Hackaday Berlin conference, and Hacker News pops up Julian Shapiro with a guide to HiFi. What Hackaday scribe wouldn’t give it a click, to while away the endless kilometres of North European Plain!

It’s very easy as an analogue electronic engineer, to become frustrated while reading audiophile tracts, after all they have a tendency to blur superficial engineering talk with pseudoscience. There’s a rich vein of parody to be found in them, but nevertheless it’s interesting to read them because just sometimes the writer gets it and doesn’t descend into the world of make-believe. Continue reading “It’s Difficult To Read An Audiophile Guide As An Analogue Engineer” →

A Look At Zweikanalton Stereo Audio And Comparison With NICAM

March 19, 2023 by 1 Comment

With how we take stereo sound for granted, there was a very long period where broadcast audio and television with accompanying audio track were in mono. Over the decades, multiple standards were developed that provide a way to transmit and receive two mono tracks, as a proper stereo transmission. In a recent video, [Matt] over at [Matt’s Tech Barn] takes a look at the German Zweikanalton (also known as A2 Stereo) standard, and compares it with the NICAM standard that was used elsewhere in the world.

Zweikanalton is quite simple compared to NICAM (which we covered previously), being purely analog with a second channel transmitted alongside the first. Since it didn’t really make much of a splash outside of the German-speaking countries, equipment for it is more limited. In this video [Matt] looks at the Philips PM 5588 and Rohde & Schwarz 392, analyzing the different modulations for FM, Zweikanalton and NICAM transmissions and the basic operation of the modulator and demodulator equipment.

An interesting aspect of these modulations are the visible sidebands, and the detection of which modulation is used. Ultimately NICAM’s only disadvantage compared to Zweikanalton was the higher cost of the hardware, but with increased technological development single-chip NICAM solutions like the Philips SAA7283 (1995) began to reduce total system cost and by the early 2000s NICAM was a standard feature of TV chipsets, just in time for analog broadcast television to essentially become irrelevant.

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How To Make A Larger Air-Cored Inductor

March 8, 2023 by 20 Comments

Radio amateurs often have a love-hate relationship with home-made inductors, sharing all kinds of tips and tricks as to how the most stable nanohenry inductor can be wound. But there’s another group in the world of electronics with an interest in high-quality inductors, namely the audio enthusiasts. They need good quality inductors with a values in the millihenries, to use in loudspeaker crossover networks. [Homemade Audio] takes us through their manufacturing process for these coils, and the result is a watchable video resulting in some very well-made components.

The adjustable former is a machined aluminium affair of which we’re treated to the full manufacture. It’s likely the same results could be achieved with a 3D printed reel. The free-as-in-beer Coil64 on Windows is used to calculate the dimensions and number of turns, and it’s set up on a jig with a cordless screwdriver doing the winding. The best technique for flat layers of turns is explained, and a coat of varnish is put on each completed layer. We’re guessing this is to stop the coil “singing” at audio frequencies.

With a set of cable ties holding it together the result is a very tidy component. It’s adjusted a few turns to get the right value with an LCR meter, however experience tells us that a tiny percentage either way won’t harm the resulting network too much. If you make your own speakers, the video below the break could be extremely useful.

Need a loudspeaker primer? We have just the article for you.

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A CRT Audio Visualiser For When LEDs Just Won’t Do

March 4, 2023 by 17 Comments

It has been a recurring feature of consumer audio gear since the first magic eye tube blinked into life, to have some kind of visualization of the sound being played. Most recently this has meant an LED array or an OLED screen, but [Thomas] has gone one better than this with a CRT television converted to perform as a rudimentary oscilloscope.

The last generation of commonly available monochrome televisions were small 5″ CRT models made in China. They never received digital tuners, so as digital TV has become the norm they are now useless to most people. Thus they can often be found for pennies on the second-hand market.

[Thomas]’s hack involves gutting such a TV and retaining its circuitry, but disconnecting the line driver from the deflection yoke. This would normally leave a vertical line on the screen as it would then be moved only by the frame driver at 50 Hz for PAL or 60 Hz for NTSC. By connecting an audio loudspeaker amplifier to the line deflection yoke he gets that low quality oscilloscope. It would be of limited use as an instrument, but few others will have such a cool audio visualizer. He’s viewing the screen in a portrait orientation, we’d be tempted to rotate the yoke for a landscape view.

It’s worth pointing out as always that CRT TVs contain high voltages, so we’d suggest reading up on how to treat them with respect.

Continue reading “A CRT Audio Visualiser For When LEDs Just Won’t Do” →

What’s Old Is New Again: A Linux PC From A Set Top Box

February 15, 2023 by 37 Comments

There was a time around two decades ago, when the new hotness was taking control of home routers to use as small Linux computers. An echo of this era lives on in the name of the OpenWrt minimal Linux distribution, in reference to the Linksys WRT54G router which started it all. Routers as small computers were displaced by small cheap Linux machines from the likes of Raspberry Pi, and the promise of discarded home network gear doing interesting stuff receded. Now it might just be back, as [Jasper Devreker] shows us an Android TV set-top box from a mobile carrier repurposed as a Linux computer that can even run a desktop environment.

The method starts as you might expect, by identifying a mystery connector as a debug serial port. This outputs all sorts of interesting boot information, but can be dropped into a uBoot shell. From here with a bit of effort the eMMC storage could be dumped, and from that the nature of the machine could be deduced. The CPU is an Amlogic quad core ARM Cortex-A53 SoC, which by a stroke of luck is a target for which an Armbian build is available. From there a Linux installation could be assembled, and even an AFCE desktop.

These boxes are handed out in the hundreds of thousands by home connectivity providers, so there’s value in this type of hack as they become available for experimenters. Perhaps it’s more useful as a small headless Linux machine than as a desktop, but we sense there are more machines to come in this line.

If you’d like a little bit of history on hackable Linux devices, have a read of one of our earliest posts featuring the Linksys WRT54G.