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Briefcase Boombox

Page history last edited by Jonathan McKinley 10 years ago

I wanted to make a personal soundsystem to be able to walk around with. I decided the briefcase was the perfect starting point for a boombox project. I began designing the briefcase boombox by making rough sketches on the back of a scrap piece of wood.

Briefcase Boombox sketch


I began by gutting the briefcase to allow for more usable space.


Next I made a paneling system to line the inside of the briefcase with quarter inch aspen.


I made the aspen lining in such a way that it all snapped together without screws or other fasteners. This process took a long time because little adjustments were constantly needed to get the pieces to fit properly. The lining fit perfectly under tension. The floor boards and the ceiling boards were made in order to allow them to spring together and therefore hold each other in place.

I then gutted a karaoke machine that was bulky and unattractive. This machine gave me a main amplifier board and battery pack pieces.

In addition to the amplifier board I salvaged a smaller amplifier board to use as a pre-amp. This pre-amp proceeds the main amplifier board and prepares the sound to be further amplified. I then began building housings to protect these amplifier boards. I decided to use the same aspen material to make hand dovetailed boxes.

After completing the boxes, I secured the amplifier boards.

I desoldered the potentiometers from the main amplifier board and reorganized them in a square configuration instead of a linear configuration.

This picture shows the finished pre-amp box.

I then drilled out the exsisting lock holes to make room for the eight inch jack and the power button. The plug and the button allow me to operate the breifcase boombox while it is closed.

These pictures show the lock hole and the eight inch jack which is used to connect to the music player on the right side of the briefcase.



These pictures show the drilled out lock hole and the main power button and the left side of the briefcase.


Next, I began work on the custom battery pack. I first cut PVC pipe to the right length to hold four D batteries. I made three of these tubes in order to fit 12 batteries to get 18 volts. Two of the tubes would be partitioned off for the main amplifier board and the third tube would be used to power the pre-amp.

I made truss shaped wooden brackets to make sure the tubes would not move. These tubes were plugged at one end with a wooden circle and a screw to carry the positive current. The other ends of the tubes were left open to allow for a spring to touch the negative side of the d batteries. I made the battery tubes so they would simply pop into place while inside the briefcase.

This picture shows the battery tubes with their plugged ends.


Next I routed the wires from the battery tubes underneath the floor boards. In order to allow the floor boards to fit flush I cut little path ways on the underside of the boards that looked like little ant colonies.


I then cut a hole in the ceiling of the briefcase to fit the speaker.


After cutting the hole I protected the aspen boards and boxes with polyurethane. Once the wood was finished I placed all the paneling back in the briefcase and I wired the speaker and the battery tubes to the amplifier board and the pre-amp. Unfortunately, the wiring process did not go smoothly because I had several problems with the power supply. It turned out that several screws that were used to pass the current from the positive side of the battery tubes, were touching the metal on the briefcase and shorting out. This problem made the batteries drain very quickly. After correcting the wiring problem I signed and stamped the floor boards.





This project was very interesting because it was a combination of both woodworking and electrical engineering. I was very happy with the outcome because I managed make an elegant custom sound system which successfully concealed amplifier boards and many feet of wiring while still looking like a casual briefcase. 









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