Introducing the MintyBlaster - a tiny amplified stereo speaker system! Rock the block with 0.5 watts of power per channel!
This is mostly a re-purposing hack - modifying a finished product into something else. Some basic tools and soldering are all it takes.
I built this a about a year ago but all parts used are still available. Where I won't be able to show you actual construction I will go over how to accomplish each step.
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Step 1: Parts
- an Altoids tin, of course. Full-sized.
- a "folding ipod speaker" like the one in the photo below. $0 - $15, depending on if and where you buy it.
These are available all over - buy the cheapest one or you may find one at a thrift store or even already own one. We use it for the amplifier board; the speakers are too big. Mine had a tea2025b amplifier chip - it's like a dual lm386 but rated for 2 x 1 watts into 4 ohms at 6v input. It doesn't matter so long as the board isn't much larger than mine (it's a tight fit in there).
I think you will be hard-pressed to breadboard something like this yourself and make is as small. If you can etch your own boards, then you could use one of the tiny surface-mount chips which do not need DC-blocking caps on the outputs. The DC-blocking caps take up the most room.
- a pair of miniature speakers, Electronic Goldmine G18251 (www.goldmine-elec.com). $1.00/ea at time of writing.
Mine were removed from an old Sun Microsystems thin client, but these are the exact same thing.
- A stereo mini-jack cord. $0
If you've owned a couple of mp3 players you probably have one you don't need. You could also use one from headphones, but the wires might be very thin gauge and hard to use.
- a 4 AA battery holder with switch, Jameco 216187 (www.jameco.com) $1.05 at time of writing.
The one thing I disliked about the folding speakers in their original form was the use of AAA batteries. They just don't last very long. Since we have no room left over in the Altoids tin for much of anything, I went with an external pack and glued it onto the back. Yeah it sorta violates the spirit of an Altoids hack, but it more than doubles the run time and it helps the whole thing stand upright without falling over. You can get this without the switch, but it's useful, as it is hard to mount the board in the tin so you can get to its power switch easily.
Step 2: Tools
You will need the following tools:
- drill (drill press preferable but hand drill OK)
- drill bits
- 0.5" chisel
- hot melt glue gun
- soldering iron
- wire stripper
- wire cutter
- screws and nuts (but I think you can hot-melt glue the speakers on if you're careful and it will work just as well)
- some small wood scraps, to be used to back up/support the tin while drilling or cutting it
Step 3: Liberate the Amp
Unless they've changed things, getting the amp out of mine was just a matter of removing screws until it was free. Make note or take photos of where the speakers and power goes on the board - mine went to little pads on the bottom of the board.
I suppose the speakers are worth saving. Maybe you can cut down the battery compartment and reuse it as well.
Step 4: Prepare the Case
Use the photo below as a guide to measurements when cutting out the speaker holes. I removed the top of the tin from the bottom by bending the little hinge tabs. I then placed the top over a small block of wood on the workbench and used the chisel and hammer to cut along the lines for the speaker holes. With a sharp chisel and a firm tap the chisel will cut right through the thin metal of the tin. This is the neatest method I can think of, unless you own some sort of laser cutter.
Next use the second photo which shows the measurements for where to make holes for the power switch, power LED and external 6v dc jack (optional). Bear in mind your board might be slightly different from mine in terms of layout. Measure twice, cut once! Again, back up the tin with something while you drill to prevent it from buckling and be sure to make a pilot hole (or dimple) before you drill to prevent the bit from wandering.
Step 5: Attach Speakers
Before you attach the speakers you might consider giving your MintyBlaster a speaker grille. A piece of window screen would work. I left it off.
I used screws and nuts in my construction but I think hot melt glue would be just fine.
After attaching the speakers, solder on the wires. Give yourself some extra wire so the case can open and close. I use teflon insulated, silver plated stranded wire. It costs more, but it conducts better and you never have to worry about melting the insulation.
Step 6: Wire and Attach Amp
Feed the power and mini-jack wires through the holes in the case. Then solder the speaker wires, battery pack wires and mini-jack cord wires to the amplifier. You are soldering to little pads so good lighting and a magnifier come in handy.
Now lay down enough hot melt glue to keep the board from shorting against the case and let it partially cool, then apply more hot glue and press the board into place.
Step 7: Attach the Battery Pack
Hot melt glue the battery pack to the back of the Altoids tin. Two-part epoxy might be stronger, but so far hot melt glue is working fine for me.
Squirt a little hot melt glue into each place where a wire enters the tin to provide strain-relief and prevent chafing of the insulation.
Step 8: Listening Test and Conclusion
The MintyBlaster isn't going to win any high fidelity awards. However, it pumps a clean 0.5w into each 8 ohm speaker, and that's plenty for moderately loud listening levels. I use it with an iPod and it's a huge improvement over the built-in speaker.
I think portability over the original has not been sacrificed. It certainly runs a lot longer on AA batteries vs AAA batteries in the original.
The tiny speakers do about as good as they could be hoped to, for the size. You will never get any real bass out of them, unless you mange a folded-horn design in an Altoids tin. Anyone up for that challenge?