home entertainment hacks

773 Articles

Bringing A Current Dumping Amplifier Back To Life

February 27, 2025 by 1 Comment

Over the years there have been many different audio amplifier designs which have found favour for a while and then been supplanted by newer ideas. One of them has crossed the bench of [Jazzy Jane], it’s a current dumping amplifier from the mid-1980s. A nicely-done home-made project on stripboard mounted on a wooden base board, it sports a power supply, RIAA pre-amp board, and the amplifier itself.

The current dumping amplifier is one that combines a small class A amplifier with a hefty class B one, and through feedback trickery uses the combination to remove the crossover distortion of the class B stage. It’s a simple yet elegant circuit with fewer parts than an equivalent class AB amplifier, and there was a time back in the day when it was all the rage. This one has an op-amp providing the class A part and a complimentary pair of Darlington pairs as the class B.

The video below the break shows the process of bringing the amp back to life, a process mostly concerned with the power supply. There are a set of tantalum capacitors which have failed, and the replacements she’s using turn out to have problems too. They’re a period part for a project of this age, but we might have been tempted to go for another capacitor type here.

The result is an unusual amplifier, brought back to life. You may have seen [Jane] feature here before, with her 1950s signal generator.

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Jeff Dunham next to a Philco Predicta TV

Jeff Dunham Finds A NOS 1958 Philco Predicta

February 8, 2025 by 14 Comments

When you see a ventriloquist like [Jeff Dunham], you probably expect to see him with a puppet. This time – spoilers ahead – you won’t. Besides his fame on stage, [Dunham] is also a collector of vintage tech and a die-hard television enthusiast. In the video below, [Dunham] has gotten his hands on a rarity: an unboxed 1958 Philco Predicta TV. The original tape was still on the box. We get to follow along on his adventure to restore this sleek, retro-futuristic relic!

[Dunham]’s fascination with the Predicta stems from its historical significance and bold design. At a time when television was making its way into American homes, the Predicta dared to be different with its swivel-mounted picture tube and early printed circuit boards. Despite its brave aesthetics, the Predicta’s ambition led to notorious reliability issues. Yet, finding one in pristine condition, sealed and untouched for over six decades, is like unearthing a technological time capsule.

What makes this story unique is [Dunham]’s connection to both broadcasting and his craft. As a ventriloquist inspired by Edgar Bergen — whose radio shows captivated America — [Dunham] delights in restoring a TV from the same brand that first brought his idol’s voice to airwaves. His love for storytelling seamlessly translates into this restoration adventure.

After unboxing, [Dunham’s] team faces several challenges: navigating fragile components, securing the original shipping brace, and cautiously ramping up voltage to breathe life into the Predicta. The suspense peaks in the satisfying crackle of static, and the flicker of a 65-year-old screen finally awakened from slumber.

Have you ever come across an opportunity like this? Tell us about your favorite new old stock find in the comments. Buying these can be a risk, since components have a shelf life. We appreciate when these old TVs play period-appropriate shows. Who wants to watch Game of Thrones on a Predicta?

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RedBox In The 80s: Meet The VHS Vending Behemoth

February 1, 2025 by 15 Comments

Redbox was a company with a moderately interesting business model—it let you rent DVDs from automated kiosks. It’s an idea so simple it’s almost surprising it didn’t appear sooner. Only, it did—all the way back in the VHS age!

Meet the Video Vendor. YouTuber [SpaceTime Junction] was able to track down one of these rare machines, which apparently formerly served an Ohio rental outlet called Kohnen’s. It’s a monstrous thing that stands taller and about three times wider than traditional vending machines, and it could hold up to 320 tapes in its robotic magazine. It’s got lashings of woodgrain, a green-on-black CRT, and the beautiful kind of clicky keys that went away after the 1980s.

[SpaceTime Junction] has a bunch of videos up on the machine, and you even get to see it powered up.  It’s a little difficult to see what’s going on, because the machine is something like nine feet wide and it’s all shot in vertical video. There isn’t a whole lot of content on these obscurities out there, so this is a great place to start. Apparently, there were recently a hundred or more of these found living in a Texas warehouse according to Reddit, so we might see more of these popping up online soon. [SpaceTime Junction] has toured that facility, too.

You can read more about the fall of Redbox, or the cleanup afterwards, in our prior coverage.

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The Audiophile Carrot

December 8, 2024 by 31 Comments

The widely quoted carrot factoid that the vegetable’s orange colour is the result of patriotic Dutch farmers breeding them that way may be an urban myth, but it’s certainly true that they can pass an audio signal in a time of need. [Julian Krause] follows up on a Reddit meme of a carrot being used to join two phono plugs, and appears to find the organic interconnect to be of good quality.

We had to admit a second look at a calendar to be sure that it’s not April 1st, but while his manner is slightly tongue in cheek it seems he’s really characterising the audio performance of a carrot. What he finds is a bit of attenuation, some bass cut, and an intrusion of RF interference pickup, but surprisingly, not a bad distortion figure.

Of course, we’re guessing the real point of the exercise is to poke fun at the world of excessive hi-fi equipment, something we’ve been only too glad to have a go at ourselves from time to time. But if the tests are to be taken at face value it seems that in a pinch, a carrot will do as a means to hook together line level audio cables, no doubt lending a sweet and crunchy overtone to the result. The video is below the break, for your entertainment.

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A Tube Stereo Amplifier, From Scratch

November 20, 2024 by 16 Comments

A conventional tube amplifier has a circuit whose fundamentals were well in place around a hundred years ago, so there are few surprises to be found in building one today. Nevertheless, building one is still a challenge, as [Mike Freda shows us with a stereo amplifier in the video below the break.

The tubes in question are the 12AU7 double triode and 6L6 tetrode, in this case brand new PSVANE parts from China. The design is a very conventional single-ended class A circuit, with both side of the double triode being used for extra gain driving the tetrode. The output uses a tapped transformer with the tap going to the other grid in the tertode, something we dimly remember as being an “ultra-linear” circuit.

There’s an element of workshop entertainment in the video, but aside from that we think it’s the process of characterising the amp and getting its voltages right which is the take-away here. It’s not something many of us do these days, so despite the apparent simplicity of the circuit it’s worth a look.

These modern tubes come from a variety of different sources, we’ve attempted to track them down in the past.

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Redbox Is Dead, But The Machines Are Kind Of Hanging On

October 17, 2024 by 37 Comments

Redbox was a service for renting DVDs from automated kiosks. The business was going well until it wasn’t anymore, and then the company went bankrupt in July this year. And yet… the machines live on. At least, that’s according to YouTuber [Smokin’ Silicon], who spotted some remaining Redbox kiosks out and about. Including at his local Walmart!

Here’s the thing. There’s not one big switch at Redbox that turns all the machines off, and even if there was—nobody hit it the moment the company declared bankruptcy. Thus, when [Smokin’ Silicon] rocked up to Walmart, he was able to flick through the movies and even add one to cart for purchase. However, trying to complete the transaction failed—the kiosk eventually reported itself as out of service. That makes sense—you’d expect payment processing to be the first thing to go down.

However, other Redbox kiosks were different. A kiosk at a Food Lion location actually still worked—and [Smokin’ Silicon] was able to complete the transaction and walk away with a Black Adam disc! On a second trip, he was able to walk away with even more!

The rest of the video dives into Redbox lore and other posts online about the status of the company, software, and hardware. Apparently, someone on Reddit was claiming they had the Redbox kiosk OS available. Meanwhile, some users have had trouble returning their discs because the company is now defunct. However, [Smokin’ Silicon] was able to return his without issue. Ultimately, though, he recommends his viewers to go out and score as many DVDs and Blu Rays as possible from the machines since soon enough, they’ll be gone forever.

The fact is, businesses are big and Kafkaesque, the kiosks are scattered all over the country, and so it’s anybody’s guess if and when they stop working. Back when this website began, a redbox was something different entirely. Video after the break.

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Phoniebox: A Family-Friendly Simple Music Box

October 5, 2024 by 5 Comments

Ever hear of the Phoniebox project? If not – tune in, that’s a hacker’s project your entire family will appreciate. Phoniebox is a software suite and tutorial for building a jukebox controlled through RFID cards, and it can play audio from a wide variety of sources – music and playlists stored locally, online streams like internet radio stations, Spotify, podcasts of your choice, and so on. It’s super easy to build – get a Raspberry Pi board, connect an NFC reader to it, wire up a pair of speakers, and you’re set. You can assemble a PhonieBox together with your kids over the weekend – and many do.

Want some inspiration, or looking to see what makes Phoniebox so popular? Visit the Phoniebox gallery – it’s endearing to see just how many different versions have been built over the six years of project’s existence. Everyone’s Phoniebox build is different in its own special way – you bring the hardware, Phoniebox brings well-tested software and heaps of inspiration.

You already have a case to house a  Phoniebox setup – if you think you don’t, check the gallery, you’ll find that you do. Experiencing a problem? There’s a wealth of troubleshooting advice and tutorials, and a helpful community. Phoniebox is a mature project and its scale is genuinely impressive – build one for your living room, or your hacker’s lair, or your hackerspace. RFID-controlled jukeboxes are a mainstay on Hackaday, so it’s cool to see a project that gives you all the tools to build one.