Simple, Powered Pocket Amplifier

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Introduction: Simple, Powered Pocket Amplifier

This is a small powered amplifier that plugs into a 1/8" stereo jack and accepts the same. Many people know nothing about amplifier circuits and would have no idea how to make one, so why don't we let a company make the circuit, and then just tweak it to meet our needs (So admittedly one does need to know a little about electrical circuits, speakers, and soldering).

This is the perfect thing to provide the extra energy needed to power larger speakers with a portable audio device without severely draining battery power. This pocket amp also allows for louder audio through headphones or small speakers. Time to blow out those voice coils!

Step 1: Hunt and Gather Supplies

For this project you will need:
-A small hearing amplifier, often called a personal amplifier or advertised as spy hearing (I used a
Radioshack brand "amplified listener" )
- Stereo headphone cable with 1/8" jack
-Screwdriver
-Solder
-Soldering iron
-2X AAA batteries (or whatever your particular model requires)
Not shown
-Connecting wire, scrap wire
-Electrical tape
-Hot glue, silicone or epoxy
-Drill and bit slightly larger than the the width of your headphone cable
-Audio source and headphones to check your progress.

Step 2: Void the Warranty

Using a screwdriver, unscrew all the necessary screws and pry the case open, remove the battery cover and get rid of any shielding (this does reduce audio quality but we need that space for some wires.)

Step 3: Check the Microphones

Identify what parts are which and what wires go where. You will need to remove the microphones and use the wires leading to them as your input source

Step 4: Identiy Your Connections

After severing your left and right microphones, mark which connections go with which microphone: left or right.

Step 5: Wire the Connections

Since someone else made the circuit, all we care about are the input and outputs, the output is already wired as a 1/8" headphone jack, and by soldering together the leads to the (now removed) microphones, red to red and black to black, we can then wire the circuit to our own input source

Here some of the wires attached to the board were too short, so I used a piece of scrap wire (yellow) to connect them.

Step 6: Strip Your Headphone Cable and Solder

Solder the red wire from your headphone cable to the combined red cables soldered to the amp circuit, and then do the same with the black wire (in my case white). the third wire may require some tweaking: put the batteries in, turn on the amp and plug some headphones or speakers into the jack. Then with the volume set low, plug an audio source into the headphone cable and listen to some music. Touch the third wire (in my case, bare copper) to different points around the circuit, then solder it to the one that makes the music sound the best. In my case it was where the black wire from the batteries was soldered to the headphone input.

Step 7: Tape

Put a tiny piece of electrical tape over any bare connections or bare wire, this will prevent short circuiting when you put it all back together.

Step 8: Exit Strategy

Drill a hole the same diameter as your headphone cable in the case of the amplifier, now all your wiring will have a way out of the box.

Step 9: Reseal and Enjoy.

lay down all the wiring and replace the cover. Then seal any gaps with the hot glue. I prefer hot glue over epoxy or other serious glues, because I can easily get back inside the case in case I need to make repairs.

Step 10: Why?

This was actually a sub-project in a larger project that had many components. I needed to make an amplifier so that I could provide two speakers (a 6.5" woofer and a public address horn) with enough power to produce a decent volume without draining the batteries from my iPod. I needed some kind of powered amplifier so that the speakers would draw power from the amp rather than the iPod; However, I needed the amp to be battery powered and small enough to be hidden in a breast pocket of a suit. I found a "amplified listener" at Radioshack and realized that it's essentially an amplifier circuit with a battery pack, all that needed to change was the input source.

The full project which I have just finished with the completion of the pocket amplifier took me over six months to make. "Max Treble" is a standalone speaker system and iPod dock.

The amp fits perfectly in his breast pocket.

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    user

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    47 Comments

    U can get one that splits it into three and dubles the power for 5 more at radio shack

    For the beginners in circuitry, the reason it sounded best was the ground wire from the headphone wire got connected to the ground of the circuit. If it sounded better connected anywhere else I would be surprised.

    can u plug in as many speakers u want or can u only have 1 or 2...?

    1 reply

    this amplifier is wired for mono and I have been able to drive two speakers, a public address horn, and a 6.5 in. sub. i honestly have no idea how many speakers it can handle

    this amplifier is $24.99
    www.radioshack.com/product/index.jsp?productId=2104056

    a lm386 alone is like almost 3 bucks but u have to do the rest yourself its like a chip but it amps it up

    Just checked on Radio Shack's web site and they have it for $24.99. I'm trying this today.

    user

    I've just buyed this radioshack appliance and i've been researching for a while. Wiring like that will make it MONO, The "stereo way" should be: Red cables: don't put them together, one cable is left and one is right channel. Just do your own tests before soldering. In the next step must be: Red with red from the jack cable and Red with White from the jack cable. Black cables: Negative for each channel so these must be put together, In the next step they must be soldered together with the "bare cooper" cable. sorry for my English. it's not my native language

    1 reply

    thanks for pointing that out. i was only wiring it for mono, so i wasn't concerned.

    my old earphone cable, which will work well for an input, doesn't have a red and a black cable, but both are unshielded. does it matter which new cable I solder onto which old mic cable? great Instructable btw

    2 replies

    No. I wired mine for mono, so i can't notice a difference

    kool! thanks heaps.

    Wouldn't wiring it like this make it mono?

    By "microphone," do you mean "speaker?" You tagged them in one of the early images as microphones.

    2 replies

    You are correct those are indeed microphones

    Oh, I'm sorry. I was unclear on what this device originally did, it would be nice if you could build that into the tutorial; just a line at the beginning that says: "In this Instructable, you'll be turning a device originally used to take in the sounds around you and output them to headphones louder than they came in to a device that can input sound from anything with a headphone jack and output it louder." That's all ramble, right there, but you can trim it down.

    It was one of my lucky thrift store finds