Portable audio rig that turned out great

December 25, 2012 By 19 Comments

portable-audio-rig

[Michael] wanted a stereo that he could use outside, be it at the beach, beside the pool, or while tailgating. He decided to build this boom box himself, and didn’t cut any corners when it came to a professional looking finish.

Because of the locale in which he plans to use the stereo he went with a set of marine speakers. They’ll have no problem standing up to water, and since they’re used in boats they should also be able to take a beating during transport. To feed it he uses a Lepai T amp which is seen above.

After cutting each piece of the case out of MDF he started working on the openings to receive the components. This involved quite a number of layout lines and some work with a compass to map out the circular openings. He built a recessed panel on the back to interface the power cord for charging. Inside is an 18 Ah battery. A set of switches lets him turn on the charger and choose between powering the amp from battery or from the power cord.

[via Reddit]

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A pair of briefcase boombox builds

November 23, 2012 By 6 Comments

Here are two different briefcase speaker projects. [Dale] built the offering on the right back in high school and the upgraded version 2.0 more recently. He was inspired to send in a tip for the projects after seeing yesterday’s suitcase full of tunes.

The first version uses a pair of speakers pulled out of a car at the junkyard. They’re mounted on some particle board which beefs up the side of the plastic briefcase. The amplifier that drives it is mounted inside the case along with a battery to power the system. [Dale] included a crude storage bracket for the input cable and since the amp can drive four speakers there are connectors on the outside for two more.

Version two has quite a bit more polish. He doesn’t show that one off quite as much, but you can see there is a LED strip on the case that serves as a VU meter, as well as a numeric display which might be battery voltage? He mentions that this blows away any commercially available systems his coworkers have brought to the job site.

Video of both rigs can be found after the break.

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Repairing a VFD driver on a car stereo

September 24, 2012 By 29 Comments

We love seeing repairs and always marvel at the ability to track down the problem. [Todd] seems to have a knack for this. He was met with a lot of adversity when trying to get the Vacuum Fluorescent Display working on his car stereo. A lot of persistence, and a little bit of taking the easier way out let him accomplish his goal.

The head unit is out of his 1994 Jeep. He knew the radio functionality still worked, but the display was completely dark. After getting it out of the dashboard he connected it to a bench supply and started probing around. He established that the data lines were still working by setting the radio to auto scan mode and testing with a multimeter. When he went to measure the cathode pins he didn’t get any reading. It seems the driver which supplies that signal is burnt out.

One easy fix would be to replace the parts from a scavenged unit. [Todd] hit the junkyard and picked up one from a Jeep that was just one model year apart from his. Alas, they weren’t exactly the same, and although he swapped out a chip (using a neat heated solder sucker) it didn’t work. In the end he simply dropped in a power resistor to use the 12V rail as a 1V at 0.1A source for the filament.

You can see his repair extravaganza in the video after the break. If you’re looking for tips on scavenging these types of displays check out this post.

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Wireless stereo add-on turns on receiver and pipes in some music

September 5, 2012 By 2 Comments

[PC486] wanted to add Bluetooth to a simple shelf stereo system. But if you’re going to go wireless, why not develop an all-in-one solution. His adapter turns on the stereo and feeds it audio all from a smart phone.

This is his roommate’s hardware so cracking it open and grabbing an iron wasn’t really an option. He needed a way to control the system without any permanent alterations. Since the unit has IR remote control capabilities that’s the most obvious way to go. But the original remote is long gone so he had to hit the Internet. Luckily the remote control codes are in the LIRC repository. He grabbed a small microcontroller, an ATtiny25, and wired up an IR led to send commands to the unit.

Next he examined the Bluetooth audio receiver board he planned to used in the project. It’s got an LED that lights up when connected to another Bluetooth device. The microcontroller knows when to turn the stereo on and when to shut it off again by monitoring that LED with a pin interrupt. Check out the final results in the clip after the break.

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A laser audio transmitter

August 31, 2012 By 38 Comments

Here’s a way of transmitting audio that makes it virtually impossible for someone else to listen in. Instead of sending radio waves bouncing all over creation, this uses the focused light of a laser to transmit audio. In the image above you can see the silver cylinder which houses the laser diode. It is focusing the beam on a light dependent resistor to the right which looks almost like a red LED due to the intensity of the light.

The simplicity of this circuit is fascinating. On the receiving end there is no more than the LDR, a 1.5V power source, and a headphone jack. The transmitter is not much more complicated than that. It includes an audio output transformer which boosts the resistance of the audio signal. This increase in resistance ensures that the laser diode modulates enough to affect the LDR on the receiving end. The transmitter uses a 3.3V supply. Check out the video after the break to hear the high quality of audio coming through the setup.

Once you’re done playing around with the transmitter you might try turning the laser into a remote control for your stereo.

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Resurrecting a Hi-Fi cabinet

July 7, 2012 By 25 Comments

[VintagePC] pulled this old stereo out of a barn. It was in pretty shabby shape, but he managed get it running again and make it look great as well.

While it had been protected from the elements, it had not been protected from the rodents. Mice had chewed their way through the fiberboard backing and made a nice home inside. He mentions that they chewed the string which operates the tuning dial, and we’re sure they were the cause of other problems as well. He gives the wise advice of not powering on an old set like this until you have a chance to assess the situation.

The insides of the amplifier were about as disorderly as the last radio repair we looked at. But after carefully working his way through the circuits, replacing capacitors and resistors as needed, he started to make some progress. The receiver coil needed to be rewound and he used wire from an old CRT monitor for this purpose. The loop antenna was remounted and the record player arm was given a new cartridge and balanced using a clever LEGO apparatus. Some veneer work and wood finishing brought the case itself back to its original beauty. We’d say the hard work was well worth it. He’s got a big piece of furniture he can always be proud of!

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Outdoor stereo helps your neighbors learn to issue noise complaints

June 6, 2012 By 23 Comments

Backyard parties are going to rock over at [Effin_dead_again's] house. That’s because he just finished building this outdoor stereo. It carries its own power supply so you can take it on the road with you, and we don’t think you’ll have trouble hearing it with the 240 Watt amplifier hidden inside.

He shared the equipment details in his Reddit conversation. A 12V lawn mower battery sits in the base of the wooden enclosure. One of the commenters mentioned the dangers of hydrogen off-gassing from that power source, but [Effin_dead_again] thought of that and included venting around the lid. The subwoofer is an 8″ Alpine, and speakers are out of a Hyundai car. The head unit has Bluetooth built in for easy connection to your smart phone. It of course has the ability to play CDs and MP3s too, and we’d bet you can tune the radio if there’s an antenna connected.

Need similar power but a bit more portability? Check out this stereo built into a cooler.

Filed Under: digital audio hacks Tagged With: , , , , , ,
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