[Samimy's] latest project is a little strange, but one man’s weird is another man’s wonderful so we’re not about to start criticizing his work. Nope, we’re here to praise the fact that his rotary phone turned reading light and audio amp is very well constructed.

He started by removing the phone housing. Those old enough to have used one of these devices will remember their bulk, and there’s a lot of unused space in both the handset and body housing. [Samimy] started by removing the speaker and microphone from the handset, and drilling a ring of holes to receive white LEDs. The circuit was wired so that lifting the handset turns on the lights.

But he didn’t stop there. A set of speakers and the audio amplifier circuitry from an old tape deck are also hiding inside the base of the phone. If you look closely in the image above you can see that he’s connected his cellphone and is listening to some tunes through the antique hardware. Take a gander at the video after the break to see construction and use of the project.

Normally when we hear of a Champ guitar amp, we think of a sweet-sounding rig that puts out 6 Watts through an 8-inch speaker. [John Chambers] of Champ Electronics wanted to build a true champion for the field of battle and came up with The Champ 1000 Watt Tube Amp, an amplifier that probably puts out enough heat to keep an igloo warm.

The amp is based on 807 valves. With some clever engineering [John] managed to coax 100 watts out of a pair of 807s, so the entire amp “only” requires 20 power tubes. The build log shows some pretty impressive examples of electrical prowess. We can’t recall the last time we featured a build with point-to-point wiring on tagboard, and [John]‘s work is some of the best we’ve ever seen.

[John] has been working on this amp off and on for a few years now, but he should be wrapping up the build sometime soon. We haven’t seen this amp in action, but we imagine it would look something like this 36×10 monstrosity. Send us a message or post a comment if you can find a video and we’ll put it up.

[Dino Segovis] wrote in to tell us about his “hack”, making an AB Audio Amplifier. The advantage of this particular amp is that the transistors never turn off, which would cause distortion. A full schematic is given in the article as well as a parts list. A complete “bill of materials” makes any circuit building project easier, especially for the beginner.

Although this is by no means a new circuit design, (a similar setup is used in car audio equipment) [Dino] does a great job of explaining how things work in the article itself and in the video after the break. He also gives some great tips about transferring your drawn circuit to a breadboard in a neat and organized way at around 5:00 in the video.

[Dino] tries to come up with something like this every week, so be sure to check back on his aptly-named site, Hackaweek.com for more fun stuff like this. Also, he mentions using the “free music archive” for his videos. This looks like a good resource for those that want to make other videos like this and need some music that legally doesn’t have to be paid for.

[Dino Segovis] wrote in to share yet another installment of his Hack a Week series, though this one is quite timely.

It was 131 years ago today that [Alexander Graham Bell] unveiled the Photophone to the world. A precursor to fiber optic technology, [Bell’s] incredibly important invention can be easily replicated in your garage, as [Dino] shows us.

The original Photophone was constructed using a megaphone and crystalline selenium cells at the focal point of the receiver, however this version can be made with easy to obtain parts. [Dino] rigged his laptop up to a speaker on which he mounted a mirror, before setting it out in the sun. The vibrations of the mirror modulate the sunlight, reflecting it onto a solar cell positioned at the end of a long, black PVC tube. The solar cell’s leads are fed into an amplifier followed by a speaker, which broadcasts the audio.

The demonstration goes off without a hitch, and while some might be underwhelmed by the technolgy, imagine how incredible it would have looked 131 years ago!

[Ben Laskowski's] been working on a Class-D audio amplifier for several months. What you see above is the most recent version of the amp. A class-D amplifier uses transistor switching (or in this case MOSFET switching) to generate the pulse-width-modulated signal that drives the speaker. This is different from common amplifiers as it doesn’t generate the kind of heat that traditional amplifiers do, making it much more efficient.

After the break you can hear it demonstrated. It’s operating off of a single-supply laptop brick and we do hear a bit of a hum coming through the system. Still, we’re quite pleased at the power and quality the small board can put out. Take a look at a post from November to get a handle on what went into development. If you still hunger for more details, [Ben's] shared the bulk of his prototyping materials in the github repository.

[Steve] was tired of looking at the speakers in his workshop and began searching around for something a little more aesthetically pleasing. Having recently received a set of hollowed out books used for hiding things as a gift, he thought that he might be able to solve his speaker issue in a similar fashion.

He grabbed a couple of books from a local thrift store and promptly removed the pages. They were replaced with cloth-covered plywood to make the device more sturdy while simulating the look of pages.

He mounted his speaker inside one of the books, and in a second installed a small 7W Class A amplifier. A third book houses a padded compartment to hold his iPod, completing the set.

[Steve] reports that the speakers are pretty much undetectable, and the sound quality is decent too. In fact, we’ve started looking for some old books to re-purpose in our workshop as well.

Hacker [Dino Segovis] is back again with the fifth installment in his “Hack a Week” series. This time around he has put together a 1/2 watt audio amplifier that would make for a great weekend project. He’s a big fan of the LM386 amplifier chip because it does so much in such a small package. Since it is so versatile, he used it as the centerpiece of his Altoids tin amplifier.

Now an audio amp inside an Altoids tin isn’t exactly a new concept, but [Dino] takes the time to discuss the circuit in detail, which is great for any beginners out there who are looking for a fun and relatively easy project. After a high-speed video of the assembly process he walks us through the completed amp, then treats us to a couple of short demos.

One thing that makes his amp different than others we have seen in the past is the addition of a 1/4” guitar jack, which allows him to use his amplifier as a combo amp/distortion effect box.

It’s another job well done, so be sure to keep reading if you’d like to watch the latest Hack a Week episode in its entirety.

A few years back, [Gio] decided to try his hand at building a couple of tube amplifiers.

The first amp was more of an experiment to see how well a DIY single-ended tube amp would sound. The amp is based off the 6T9 design created by Spare Time Gizmos, and incorporates a pair of 6T9 vacuum tubes, hence the name.  He wired things up in an afternoon, then got busy drilling holes in a baking pan, where he mounted the amp. Bear with us for a second, it’s not as bad as it sounds. The amp actually looks pretty good mounted in the dark black steel, and this sort of enclosure is far cheaper than most DIY amp enclosures. He says that he was sure to be extra careful in isolating all of the electronic components from the metal chassis.

The second amp was built to test the performance differences between Pentode-mode and Ultra-Linear mode configurations. While both amps share a substantial amount of the same components, his UL amp benefits from slightly better capacitors and an uprated power supply, not to mention a more conventional case.

Both amps sound great, according to [Gio], but should be paired with efficient speakers for the best experience. He does note that the ultra-linear amp is the better choice, mounting options aside.

[Thanks, Philippe]

[via RetroThing]

In need of an amplifier for his home entertainment system [Afroman] decided to build an amp rather than buying one. If nothing else, doing it himself allowed for a form factor that can’t just go out and buy.

He designed the project on two separate boards, one for the power supply and the other for the amplifier circuit. Both are of his own design, and although he doesn’t share the schematic, we know he’s based his work on a National Semiconductor reference design for the LM4780 audio amplifier chip. There’s a few other clues, like his mention of the toroidal transformer seen at the left in the image above and hi-res photos of the unpopulated board that has component values printed in the silk screen.

The final design allows him to get great performance out of his speakers with a very clean look. You’ll need to be logged to the forum linked above to view all of the images, but we’ve embedded three more of them after the break to whet your appetite.

Oh, and cost? This gets up there, just sneaking past the $500 mark.

[Thanks AB]

[Bob] has been busy lately putting the finishing touches on three different projects that he plans on entering into the 555 Design Contest.

His first entry is a low-power H-bridge, which can be used to drive small servos. While he admits that it is a bit odd to build use a 555 timer to construct an H-bridge, they are cheap and plentiful enough to justify their use. Check out the video below to see the simple H-bridge controlling a servo.

[Bob's] second entry is quite a bit more complex than his H-bridge. His secret knock detector listens for a pattern of knocks, triggering a relay if the proper cadence is detected. If a knock is heard, the first 555 timer starts, listening for another knock within a specific time range. If a knock is heard during this period, the next timer is triggered, and the process is repeated. Subsequent knocks must be timed correctly, or the circuit halts, waiting for a reset timer to expire before listening is resumed. It’s a bit hard to get the knocks just right, but that should be fixable with a few small tweaks.

The third entry he sent us is a project that is pretty common, though with a somewhat uncommon implementation. Class D amplifiers are often built as low-power headphone amps for personal audio applications. He liked the idea of a Class D amplifier, but wanted to build something with enough power to listen to his music in a small room. To accomplish this task, he looked over the internal block schematics of a 555 timer and constructed a pair of high-power 555 timers himself, using discrete components to mimic those usually found in the 555 package. His results were decent, though admittedly not of the highest quality, and could be tweaked a bit to provide better sound fidelity.

Continue reading to see videos of each project in action.

We love all of the projects that are coming out for the 555 design contest, so we thought we would share a couple more that have caught our collective eye.  Have a 555 project of your own? Be sure to share it with us, and keep an eye out for the contest submission dates. Read on for a few of our project picks.

A wonderful combination of a number of commonly used ICs, this amplifier with built in visualizations features the LM3915 as a circular VU meter, a TDA2003 audio amp chip, as well as a 555 to control an LED “breathing” light. Sure the role of the 555 is limited as of now, but there is plenty of time to beef up any designs before the contest is over.

A follow up to a previous project we covered, this revamped low cost fuel injection tester, this build by [Dino] has taken in to account some of the suggestions by Hackaday commentors to step up the submission. Be sure to check out the explanation video, as well as a video in action.

This odd looking perforated disk acts similarly to a record, however it uses optical sensors in place of a needle to sense notes of a “song”. Using 555 timers to generate the audio signals, this project definitely has a distinctive sound to it. Right now it is hand turned, and the resolution seems a bit low, but a quick servo or stepper add on and some more fine tuning could yield a very unique music box build.

[Tristan Chambers] picked up an old speaker box some friends acquired at a yard sale. It didn’t have any inputs, and there weren’t any tuning knobs like a radio would have, so it’s a mystery what this was originally used for. [Tristan] traced out the circuit and figured out where he could input audio signals which allowed him to hook up an iPod, but it was mono and not very loud. He ended building his own vacuum tube preamp from a schematic he found on the Internet so that he could use it with an electric guitar. As the video after the break shows, the box not only puts out some pretty good sound but it’s nice and loud too.

[Nikita] made a great find while cleaning out his garage: a set of audio amplifiers from a 1986 Volvo. After a bit of testing, he dislodged a stuck relay and set out to use these amps for a home audio system. He grabbed some left over brackets from his TV mount and used them as rail mounts. On the back he wired standard speaker connectors and RCA connectors to the wiring harness for the amplifiers. The final aspect is powering up the device, for which he used his ATX psu previously modified as a bench supply. 130-Watts of power for the cost of a few connectors.

We surprise to find we haven’t covered this common ATX bench-supply conversion before. What we have seen is an adapter to use one as a bench supply.

It’s pretty creative to use a 9v battery as an enclosure. That’s what [Osgeld] did when building this amplifier. There are several advantages; they’re easy to find, it keeps a bit of the dead battery out of the landfill, and this method provides a built-in connector for a 9v power source. In this case the circuit is built around a LM386 audio amplifier. It’s glued to the back of a potentiometer and wired up with the other components for a package smaller than a quarter. A stereo jack reside in the side of the battery case with a cable and alligator clips for connection with a speaker. Now the amp can be quickly connect to any 4-8 ohm speaker.

A few weeks ago we saw [Jaroslaw's] universal credit card spoofer. Now he’s sent in a project that incorporates an amplifier into a center speaker for use with an iPod or any device with an audio jack.

The build has two main components; an LM4950 audio amplifier and a center channel speaker he picked up for $3 at Goodwill. The circuit used is straight from the datasheet and he’s provided the four necessary resistor values for you in his writeup. An old set of headphones was butchered for the audio connector and DC power can be provided by any 6-12V source.

The final circuit was built on some protoboard. The speaker housing has plenty of room to fit everything in for a nice finished look. Pretty simple, and except for the IC, this should be an easy salvage project for most folks.