[Ynze] has built an audio amplifier that looks and sounds great. His amplifier uses a National Instruments (now TI) LM3886 Overture series 68 Watt power amp. The LM3886 places [Ynze’s] amp squarely in the “Gainclone” catagory. Gainclone or Chipamp are terms long used by the DIY community to describe audio amps based upon highly integrated semiconductor amplifiers. The Gainclone name stems from the original Gaincard audio amplifier sold by 47 labs. The Gaincard used less than $100 USD of parts when it was introduced in 1999. It sounded good enough to command a $3300 USD price tag on the audiophile market. The low parts count and simple construction spawned the audio DIY community to build their own versions of the Gaincard. Hundreds of variants exist now, and wading through the different versions can be a bit of a daunting task. [Ynze] found a basic design that works, and built from there.
One of the interesting things about [Ynze’s] amp, as well as many of the Gainclones, is the fact that they use no circuit board. All wiring is done point to point. resistors are soldered directly to the pins of the amplifier chip. This can be some tricky soldering for beginners, but several PCB kits are available. [Ynze] built his amp in two cases. One case holds the power supply, and the other contains the amplifier itself. [Ynze] is using a large toroid transformer to drop his local 230V mains down to +25V and -25V. The amplifier circuit itself is simple – a few discrete components surround the LM3886 and it’s heat sink. [Ynze] also did some very nice carpentry work on his wood chassis. The resulting amp looks like it’s right out of the 1960’s – but hides 1990’s electronics inside.
Continue reading “Build a Simple Audio Amp”
This Bluetooth Audio Adapter is meant to connect a Bluetooth audio source (like a smartphone or tablet) to a speaker system with a plain old line-in connection. It has the ability to automatically connection when the Bluetooth device comes into range. Sounds convenient until [Andreas Pösch] points out that he still has to switch the speakers on and off manually. This hack automates the entire thing using a bit of additional hardware.
If you look closely you’ll see that the black cables have barrel jacks. This is a power pass-through rig that he whipped up. The protoboard includes a 7805 linear regulator which feeds power to the green circuit board in lieu of it’s original power adapter. A MOSFET switches outbound power headed for the speakers. All of it fits inside of the original enclosure, and he only had to add one port for the AC adapter.
This would be absolutely perfect for an antique radio retrofit. One of these adapters can be had for just over thirty bucks!
It’s an understatement that [Troy] is not impressed with the distortion circuitry built into this guitar amp. He picked it up for $40 on Kijiji (basically local classified ads run by eBay) so he wasn’t afraid to get elbow deep in its inner workings to see what was going on. It only took him a few minutes to solder together the distortion circuitry that fixed it. Figuring out what needed fixing is another story.
[Troy] uses some colorful language and metaphors to illustrate his disdain for the sound of the overdrive option. He hooked it up to an oscilloscope and his trained eye immediately tells him that it’s not working as it should. After studying the PCB and working out a schematic he reworked the circuit with this pair of diodes and a resistor. It still uses a bit of filtering on the board, but does away with all of the other cruft. What remains is a cheap amp, but one that actually functions.
This AM radio looks a bit like it did coming out of the factory. But there are a lot of changes under the hood and that faceplate is a completely new addition. The project really is a restoration with some augmentation and [Michael Ross] did a great job of documenting the project.
The Kenyon radio was built in 1946 and uses vacuum tubes for the amplifier. Considering its age this was in relatively good shape and the first thing that [Michael] set out to do was to get the electronics working again. It involved replacing the messy collection of capacitors inside. He then cleaned up the tubes, checking for any problems, and put the electronics back together to find they work great!
He cleaned up the chassis and gave it a new coat of finish. The original dial plate was missing so he built a wood frame to match a dial scale he ordered. The bell-shaped brass cover hides the light that illuminates the dial.
He could have stopped there but how much do people really listen to AM radio these days? To make sure he would actually use the thing he added an Arduino with an MP3 shield. It patches into the antenna port via a relay, injecting modern tunes into the old amplifier circuit. Catch a glimpse of the final project in the video after the break.
Continue reading “AM tube radio restored and given MP3 playback too”
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.
Continue reading “A pair of briefcase boombox builds”
Take the party with you by building your own boomcase. It’s an amplifier and set of speakers built into luggage. It uses an audio jack to connect to your favorite music player, and with a bit of added protection — like grills for those speakers — it could still be gently used to transport your wardrobe.
A 1960’s suitcase was mutilated for this build. [Jay] must have already had it on hand because combined with some used parts he claims to have only spent $50 total. After trying out a few different speaker orientations on a piece of cardboard he covered the outside of the case in blue painter’s tape and started cutting holes. The amp he chose has a nice face plate which happens to fit nicely on the top side of the case. For now he’s powering it with a 10,000 mAh (ie: 10 Ah) portable device recharging battery. But as you can hear in the demo after the break this seems to have no problem supplying the system with enough power.
Continue reading “A suitcase full of tunes”
[Quinn Dunki] is adding wireless audio to all of the rooms in her home. She’s going with Airplay, snatching up used or refurbished Airport Express units because of their ability to work with both her existing WiFi and the Airplay protocol. The last piece in the puzzle is to get an Amp and she chose the small unit seen above. The problem is that it was dead on arrival and she couldn’t get the company to respond to her issue. So she cracked it open and fixed it right up.
The offenders are the three electrolytic capacitors at the top of the picture. She took some close-up images of each and you can’t miss the fact that they’re blown out. These are often among the higher price-per-unit parts and manufactures try to pinch the penny as much as possible. Add to it the heat in a small enclosure like this one and you’ve got a failure. [Quinn] dug through her junk bin but the size of the replacement had to be a perfect match so she ended up putting in a parts order. The new caps fit and work perfectly as you can hear in the clip after the break.
Continue reading “[Quinn] resurrects an amplifier that experienced death-by-capacitor”