Class-D Audio Amplifier Makes It From Breadboard To PCB

May 21, 2011 by Mike Szczys 17 Comments

[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.

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DIY Hidden Bookshelf Speakers

May 11, 2011 by Mike Nathan 10 Comments

hidden_speakers

[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.

LM386 Altoids Tin Amp

May 1, 2011 by Mike Nathan 30 Comments

altoids_amp

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.

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Baking Pan Tube Amp Sounds Better Than You’d Expect

April 6, 2011 by Mike Nathan 32 Comments

baking_pan_tube_amp

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]

Don’t Buy An Amp, Build One To Suit

March 21, 2011 by Mike Szczys 22 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.

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A Trio Of Last-minute 555 Timer Projects

February 28, 2011 by Mike Nathan 5 Comments

[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.

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More 555 Projects To Enjoy

February 7, 2011 by James Munns 9 Comments

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.

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