Yep, that’s a picture of a Laptop rocking out on an electric guitar. In what can only be described as a truly bizarre hack [CNLohr] discovered that the RF noise from the computer can be used to play music through the guitar’s pickup.

Check out the clip after the break to hear an annoying, but very discernible rendition of Jingle Bells. Once [CNLohr] stumbled onto the fact that changes in what the graphic processing unit is doing was affecting the pitch detected by the pickup he started writing some code. Now he’s got a program that automatically calculates the size of the window, and produces a white square on a black background to dial in the GPU at the right frequencies.

He mentions in the notes accompanying his video that he had to turn off Vsync to get this to work right. We don’t understand why but we’d love to hear what you think in the comments.

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]

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.

Hard at work on making this 1960′s Fleetwood audio console usable again, [Travis] packed a lot of power into the retro case. Both the radio and turn table had stopped working but the cabinet looks great and the speakers still work. In the lower center cavity you’ll now find a full computer motherboard and replacement amplifier. A new turntable has been added with an interesting vibration-dampening shelf to support it. [Travis] built the shelf with a void in between two layers of wood which he filled with sand to help with isolation. The remote control for the amp also needed some work as the receiver is pointed to the back of the unit. To fix that a second IR receiver found a home behind the fabric for one of the speaker grates. That receiver is monitored by an ATmega168 microcontroller and signals are repeated back to an IR LED mounted near the amplifier.

This vintage radio can play AM, FM, and MP3, all with a classic sound. Inside you’ll find a new AM radio tube-amp, providing the functionality you’d expect from the device. The rest of it comes from a conglomeration of parts; an FM receiver board from another radio and an MP3 player with remote control and USB connector. The classic sound we mentioned above comes from an AM modulator. That’s right, the auxiliary audio boards aren’t connected directly, but are broadcast on the AM band so that your latest MC Lars album has the same sound quality as the traffic report.

Check out this similar project from last year that adds RDS to a vintage radio.

[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.

[Billy] wanted to use the audio connector on his MacBook Pro for input and output at the same time. He knew it could be done because Apple sells headphones with built-in microphones that work with the computer. He set out to build a breakout box so that he could connect the components of his choice to the single port. Using a scart-RCA adaptor box he scrapped the scart plug and wired the RCA jacks to the Apple headphone wires. He can now patch the pickup of his guitar to the mic connector, send it through the MacBook, and run the output back to his guitar amp.

[Alessandro Lambardi] had some vacuum flourescent displays that he pulled from junked VCRs. His latest project is an experiment to use one of the VFDs as a headphone amplifier. This means he’s trying to use them as vacuum triode amplifiers, aka vacuum tubes. He did get it to work but as he suspected, the output is fairly low power. It may be possible to use this setup as a preamp and build an actual tube amp to use along with it.

Update: Thanks to [Fallen] for mentioning that we’ve covered this concept in the past.

[Thanks Muris]

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.

[Hydronic] did some tests to make his own current sensor using a c-clamp wrapped with wire. He tried several different cores including an aluminum carabiner, the C-clamp, and what he calls a u-lock (removable chain link). There is some success here that could be improved with cleaner winding and by adjusting readings based on the length of wire used in the wrapping.

This did make us perk up a bit right off the bat. Reader [Mure], who tipped us off about this, suggested that this could be used to make your own Kill-a-Watt without including it in the circuit. We made the jump to house monitoring. We’d love to have a data tracker for our home circuits to curb wasteful energy use. Perhaps we’ll try to make our own sensors and produce a diy Cent-a-Meter.

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.

[Niclas] sent us his home made tube amplifier. For the case he used a computer power supply unit, took out the guts and replaced them with the amplifier board. He based this build off of an existing design but took a more minimalist approach. The wooden face plate has an on/off switch, an audio jack, and volume control. Apparently, the tubes are floating loose inside of the case. We’d recommend a more secure mounting method for these delicate parts.

Having the right tools and workspace are key to successful soldering. The actual technique is pretty simple. We will cover all the basic tools you need, the key to good soldering, and how to undo your mistakes or harvest components from old hardware.

The first thing you’ll need is a decent soldering iron. Weller makes a decent product, but RadioShack’s are dirt cheap if you’re in a hurry. My favorite iron was a temperature controlled Tenma with LED temp display (sadly lost from a crappy storage unit along with my oscilloscope).

Most soldering stations come with a sponge; they get lost and they tend to hold onto bits of solder. I actually prefer to use a paper towel instead. Either way, wet it down and give it a squeeze so it’s not sopping wet. If it dries out, it’ll burn when you wipe your iron on it.

Buying the right kind of solder is just as important. It comes in various thicknesses, metal alloys, and core types. I won’t get very deep into the alloys. Generally, you want 60/40 (60% tin, 40% lead). Most modern electronics are lead free, but for hobby work lead is fine. Just wash your hands when you’re done! The solder produced for plumbing work is usually very thick (left hand side) and has a solid metal core (or worse: acid core). For electronics work, you’ll definitely need rosin core. The rosin acts as flux for the solder, allowing it to flow onto and attach to the metal. You can certainly use liquid flux/rosin, but it’s usually not easy to find locally. For thickness, I always buy the thinnest rosin core I can find. To sum up: you want thin, rosin core, 60/40 solder.

Not all iron tips are created equal. For fine work, I always reach for my 15 watt Weller pencil iron. It has the smallest tip I could find, and I ground an even finer point on the tip with my rotary tool. The bigger iron is an inexpensive RadioShack station that I keep in my office to handle favors for coworkers.

Every so often, the tip of a soldering iron needs a little maintenance. If the end of the iron isn’t tinned, as in bright and shiny when you wipe it down, you’ll have a hard time getting solder to melt. Think of this stuff as a sort of pumice stone for your iron. Heat the iron up and rub the tip in the cleaner. The cleaner will melt a bit and your soldering iron should work better than ever.

Securely holding the work piece is important, but your hands will be busy with the iron and solder. My current favorite tool is this Panavise Jr. which runs about $25. Props to Ladyada for unknowingly turning me onto Panavise products. If you need something cheaper, you can score a set of helping hands – it’s set of alligator clips connected to a weighted base. They work great and I still use them for smaller soldering projects.

Some projects require extra fine attention to detail. A giant magnifying glass lamp comes in handy when visually inspecting for shorts and dealing with surface mount problems (I inherited this one one from my grandmother). You’ll be fine without one, but they’re great when you need to work on really small components or when your eyes are getting tired.

For one-off projects, prototyping boards from RadioShack are handy. They’re cheap, easy to get, and making a connection is as simple as bridging your solder across the copper pads.

Before investing your time soldering parts together, it’s a good idea to prototype your circuit. Breadboards like these are great for preventing frustration later on. When I tried to buy my first one, I was about 10 years old. Nobody knew what the hell I was talking about and the local RadioShack apparently didn’t keep them in stock. People at RadioShack kept trying to sell me kitchen cutting boards. After about a year of wondering if [Forrest Mims] was insane, I finally visited another RadioShack that actually had them.

Don’t bake your bits. Passive components like resistors or small ceramic capacitors don’t usually suffer any problems from being heated up, but you should still pay attention to how long you’ve been cooking them with your soldering iron. If you’re having problems getting a solder joint just right, let the parts rest for a few minutes so they have a chance to cool off between soldering rounds.

Integrated circuits like this logic chip are usually far more sensitive to heat and static than passive components. Sockets are cheap insurance against blowing a chip.

RadioShack sells the small red handled clip as a heat sink. It’s okay, but a generic hemostat like the one above works and holds on even better. They’re also great for saving your finger tips from burns by holding wires in place while you solder them.

To successfully solder a component, don’t melt the solder on the iron. Put the iron against the copper on the board (solder pad) and the component you want to attach. Give the iron a moment to heat up both of them. Then melt the solder on the component and, if needed the copper pad.

Do not melt the solder on the tip of the iron. Sometimes it’s necessary to melt a small amount on the iron to facilitate heat transfer, but to achieve a good connection, you want the solder to melt and flow onto the component leads.

Heat up the component with the iron just before applying solder!

Once the joint is good, the soldering iron can be used to remove small amou
nts of excess solder from the joint.

Wipe the solder and burn rosin off by pulling the tip across your wet sponge or paper towel.

The joint should be good if the solder flowed onto both the copper pad and the wire lead of the component.

Now you’ll need to trim down the excess wire lead of the component. If you use diagonal cutters, the piece you cut off will probably fly through the air. These flat cutters are my favorite: the metal wire stays still and the resulting edge isn’t nearly as sharp.

Nobody’s perfect. Sometimes we need to remove a bad component or undo a mistake. Desoldering braid works sort of like a sponge for excess solder.

To desolder something, just place the braid over the target and apply your soldering iron over the top. The heat should transfer through the braid and the melted solder will flow onto the the copper like oil though a wick. For larger amounts of solder, I normally pull out my bigger iron. For small amounts, even the pencil iron does the trick.

For larger desoldering jobs, like recovering components, a desoldering iron works wonders. The hotter the better, so let it warm up for a while before using it.

Compress the bulb with your thumb before you touch the board with the iron.

Once it’s in position, give it a moment the heat the solder and release the bulb. The bulb with suck up the solder through the hollow tip. Larger components might take a few hits, but smaller ones usually only take a single pull.

We’ve covered all the basics: the tools, soldering and desoldering. If you’re looking for a good starter project, I highly suggest taking a shot at making your own headphone amplifier. I built this one from RadioShack parts (I had some high end opamps in my parts bin). It’s a rewarding, low cost project. If you want an even more illustrated guide, check out these basic videos from NASA or even this collection of videos from Solder.net.

When you need a rigid, vibration-free chassis for your amplifier, look no further than a roasting pan. I’ve used cast cement for subwoofers, but using a cooking pan bolted to a heavy wooden chopping board is a cheap way to get a rigid surface on which to build audio gear. The amp circuitry used by [Mark] is not complex, but it gets the job done. The “oxygen free copper cable” and “pure silver wire” are not needed, just make sure you have a solid mechanical connection. In other words, just tin your wires, bend small “u” shapes at each end, hook them together, and apply solder to the heated ends. Alternatively, hold the ends of stranded wires parallel to each other and twist the ends together before tinning, then solder. Test everything with a multimeter while moving wire joints to make sure you have no weak connections. Now you won’t waste your money on hyped-up cabling materials.

Thanks to [Gio] (who seems to have some personal audio projects as well) for the tip.