Free formed circuit protected by a brick of crystal clear resin

The look of this crystal clear resin brick is pretty amazing. [Rupert Hirst] decided to encase his amplifier circuit in a block of polyester resin. We just hope he got everything in his circuit right because there’s no way to replace any of those parts now!

He deserves a lot of credit for working out a visually pleasing way to mount each component. There wasn’t any type of substrate used, but a few lower gauge wires were picked as the rails and they add some mounting stability. Before casting, he took the case of each of the three jacks apart and sealed the seams with some of the casting resin to prevent the final pour from filling them up.

Eagle CAD was used to design the mold. He printed it out on some card stock, then used a hobby knife to cut the pieces out and super glue to assemble them. A second layer of super glue was run on each seam to ensure they’re water tight. After the casting was made [Rupert] spent plenty of time sanding, routing, and polishing the brick to achieve this look.

This makes us wonder about heat dissipation. Do you think it will be a problem? Tells us what your opinion by leaving a comment.

SpeechJammer puts an end to annoying speakers

If you’ve ever had to deal with people disturbing your peace and quiet by yammering on with their cell phones, you might be interested in the SpeechJammer.

The idea behind the SpeechJammer is fairly simple: It’s very hard to speak if your words are recorded and played back to you a fraction of a second later. This is a real psychological phenomenon known as delayed audio feedback that also has a beneficial effect on stuttering.

According to the researcher’s writeup (PDF warning), the SpeechJammer works by measuring the distance to the ‘target’ with an ultrasonic distance sensor and records the speaker’s voice with a shotgun mic. The recording of the spearker’s voice is delayed for about a fifth of a second and then played on a speaker on the front of the gun.

The researchers tested two conditions: ‘reading news aloud’ and a ”spontaneous monologue.’ Subjects who were reading news aloud had their speech jammed more often than those with the monologue, but the results look fairly promising. There’s only one video of the SpeechJammer in action (available after the break), so we’d like to see a few Hackaday readers build their own ‘shut up gun’ and send in a demo with an annoying talker to validate the results.

[Read more...]

Rotary phone-light-amp could be filed under bizarre

[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.

[Read more...]

High Voltage Hacks: A 1000 Watt tube amp

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.

Build Your Own Class AB Audio Amplifier

[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. [Read more...]

[Dino] celebrates the 131st anniversary of the Photophone

photophone_demonstration

[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!

Class-D audio amplifier makes it from breadboard to PCB

[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.

[Read more...]

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