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Portable Music Amplifier

A powerful portable amplified speaker with built in rechargeable battery.

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I love listening to music on the go, but commercial portable amplifiers are too pricy and some aren't nearly loud enough. I designed this project with a few goals in mind: To make something inexpensive, powerful, reliable and small.

This device is based around the PAM8403 Class-D amplifier. It's a stereo amplifier with 3W of output power per channel. The device is powered by a 2200mAh lithium polymer cell. The battery is charged with a USB cable. An AtTiny88 AVR manages the system and protects the lithium battery from damage. The case will be 3D printed with ABS plastic, and then smoothed using an acetone vapor bath. 

I've bought enough parts to make 10 units of this design, so I can sell these to anyone who is interested.

  • Constant Improvement

    Adam Oakley09/16/2014 at 21:01 0 comments

    As I solder more of these PCBs together and assemble cases, I keep learning better ways to do things. I've made some minor changes to the case design which help it print more reliably, as well as to make it easier to remove a PCB if it needs servicing. 

    I have also experimented with adding a port hole to the rear of the speaker box. I did a lot of reading on speaker port theory and figured I'd give it a go. With a port hole on the rear of the box, bass came out somewhat less distorted, but at the same time certain parts of songs now had horrible distortion at high volume. I decided to go back to the original design. I ended up modifying the speaker grille to allow better airflow and now I'm fully satisfied with the case design.

    I've added a picture which shows the latest version of the speaker case. To make it like that it was sanded flat after printing and then smoothed out with an acetone vapor setup which you can take a look at here.

    On another note, the battery life of this device is amazing. I had initially wanted 6-8 hours of battery life but I've ended up with much more than that. I've been testing the first unit I built which so far has lasted around 20 hours from a full charge. It's not even telling me the battery is low yet, so I'm not sure how much longer it will last. It seems the class-D amplifier I used is quite efficient.

    If you have any questions about this project and how I made it, feel free to ask. I'd be happy to answer.

  • Design Complete!

    Adam Oakley07/27/2014 at 06:54 0 comments

    I can now say I'm satisfied with the design of the case and the firmware. I pulled out all the power-saving tricks I could, and the AVR system monitor draws very little current when the device is off. I've also been tweaking and finalizing the case design. Both pieces of the two piece assembly now fit together snugly and the PCB lines up perfectly with the rear holes. All that's left to do now is to start building these things, and smoothing the cases with acetone vapor.

  • Status Update

    Adam Oakley07/17/2014 at 22:11 0 comments

    I've been working on this project for a while now, and most of the hard work is already done. I designed the circuit and layed out the PCB. I had the PCBs manufactured by DirtyPCBs. All the components have been purchased and are ready to go. As you can see from the pictures, I've been testing designs for the 3D printed case. I've also soldered one PCB and verified that the design works.

    There are still a few things that need to be finished. I need to write the software for the AVR and test it. I also need to finalize the model for the case. After that I can begin printing cases and build a few finished units.

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