Frankenstein, an all-tube home theater amplifier

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Here’s an exercise in excess if we’ve ever seen one. While working on his undergrad at Michigan State, [Gregory] thought it would be a great idea to build an all-tube home theater system. He calls his seven-foot tall rack of amplifiers ‘Frankenstein,’ and we’ve got to agree this build is an impressive monstrosity of engineering prowess.

[Gregory]’s Frankenstein is a complete 5.1 home theater system. In the interests of sanity, the majority of the equipment in the rack is off-the-shelf gear including a CD player, surround sound processor, and a beautiful McIntosh solid state preamp. The power amps, though, are where this build really shines.

For the sub, [Gregory] built a wonderful monoblock tube amp, able to push nearly 300 watts into a subwoofer. The other channels for this home theater system are amplified with a huge four channel tube amp providing 480 watts per channel. In total, there are 23 tubes in [Gregory]’s amplifier system, enough to consume 20 amps of filament current.

You can check out [Gregory]’s demo video of his system after the break.

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Cute little amplifier has a tube pre

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While you won’t catch us in an argument with an audiophile regarding the sound quality of tube vs. solid state amps, there is a general consensus that tube amplifiers sound much better than their transistorized brethren. Actually building an all-tube amplifier, though, is a bit harder than one built around common ICs – there are transformers to deal with and of course very high voltages. One solution to get the sound of tubes easily but still retaining the simplicity of integrated circuits is a hybrid amp, or a tube preamplifier combined with a solid state power section. They’re easy enough to build as [Danilo] shows us with his hybrid tube amp design (Italian, translation).

[Danilo]’s design uses two ECC86 for the left and right channels powered by a 12 Volt supply. Each channel is sent through a tube and then amplified by a TDA2005 20 Watt power amplifier. After plugging in a CD player, the result is a clear, warm sound that can put a whole lot of power through a speaker.

A pair of briefcase boombox builds

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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A suitcase full of tunes

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.

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[Quinn] resurrects an amplifier that experienced death-by-capacitor

[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.

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70 watt amp uses an ATtiny

If you’re looking for a DIY amplifier project made with a minimum of parts, this is the build for you. [Rouslan] created a 70 watt class D amplifier using an ATtiny45 and just a few dollars worth of additional components.

A class D amplifier simply switches transistors of MOSFETs on and off very rapidly. By passing the signal produced by these MOSFETs through a low pass filter and connecting a speaker, a class D amp is able to amplify a signal very efficiently. Usually, these sort of amp builds use somewhat esoteric components, but [Rouslan] figured out how to use a simple ATtiny microcontroller to drive a set of MOSFETs.

In [Rouslan]’s circuit, the audio signal is passed into the analog input of an ATtiny45. Inside this microcontroller, these analog values are sent to the MOSFETs through a PWM output. [Rouslan] threw in a few software tricks (explained in revision 2 of his build) to improve the sound quality, but the circuit remains incredibly simple.

[Rouslan] posted a video going over the function of his ATtiny amp, and from the audio demo (available after the break), we’re thinking it sounds pretty good. Amazingly good, even, if you consider how minimalistic this 70 watt amp actually is.

Thanks [Alec] for sending this one in.

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Outdoor stereo helps your neighbors learn to issue noise complaints

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.