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How-to Woodworking

Build a DIY Passive Cell Phone Amplifier

DIY Passive Cell Phone Amplifier

If you have a cell phone and enjoy music, you need one of these. This passive cell phone amplifier delivers an 8-10 decibel boost to your phone, while improving the sound quality. It also serves as a docking station, allowing the phone to be charged while sitting in its cradle.   This simple design has all the attributes of a great “production project”, so if your holiday gift list includes a bunch of cell phone owners, this project might be an option for you.

It will definitely earn you plenty of “oohs and ahhhhs” when the gift wrap is removed from this bad boy.

 

I built this one out of walnut, but you can use whatever wood suits your tastes. It’s doesn’t require a ton of material, so it’s also a great way to clean out the scrap bin.

Cut the parts. Use your table saw to cut the parts to the dimensions shown in the diagram.

 

DIY Passive Cell Phone Amplifier

 

DIY Passive Cell Phone Amplifier

 

Cut the base in half. Draw a line from corner to corner across the face of the base. Then use a bandsaw to carefully cut the line, guiding the cut directly onto the line rather than one side or the other.  Both pieces will be used so it it’s important to divide the piece evenly.

 

DIY Passive Cell Phone Amplifier

 

Make a flat even top. After you’ve sanded the base pieces smooth, set the pieces next to one another and use a block plane to flatten both points and make the even. This will provide a better surface for the phone to rest upon.

 

DIY Passive Cell Phone Amplifier

 

Create a notch for the cord. Using a table saw, nibble away an opening on the bottom of the back panel that will be large enough for the cord to travel through.   Use a chisel to clean up the blade marks and chamfer the edges to minimize wear on the power cord.

 

DIY Passive Cell Phone Amplifier

 

Cut an opening on top for the phone.   Make sure that the opening will accommodate your phone.

I have found that an opening of 5/8” x 3.5” works for most phones and most cases, but there can always be an exception to that so be sure to measure and leave some wiggle room in each direction. Use a bandsaw to remove the waste.

 

DIY Passive Cell Phone Amplifier

 

Assembly time. Because there are only five small parts, assembly is pretty straightforward. Be sure that your cutouts for the cell phone and the cord travel are on the same side of the assembly, or you will have problems later.  

I find that traditional hand screw clamps work best for this assembly because they can dial in the pressure evenly across the faces of the amp. If you don’t have screw clamps you can use bar clamps as an alternative.

 

DIY Passive Cell Phone Amplifier

 

Cut each end to a 45-degree angle. This cut can be made on a miter saw if you have a 12” model, or a bandsaw.   The angled ends help direct the sound out toward the listener.

One of my early prototypes for this project did not have angled ends, and I found that the angles added to both the volume in the room as well as the quality of sound.

 

DIY Passive Cell Phone Amplifier

 

Sand, sand, sand! Make everything as smooth as possible by sanding through 400 grit using a random orbital sander. Also use the sander to round over all the sharp edges.

Do some hand sanding to soften the edges around all of the openings on the amplifier as well.

 

DIY Passive Cell Phone Amplifier

 

Finish line. Apply whatever finish you want for this. I used Walnut Oil, which I generally use for salad bowls, because I was giving this as a gift the next day and I didn’t want the finish to stink.  

Any penetrating oil or surface finish such as polyurethane will do just fine on this project.

 

To watch a video of this project being built, click here.

DIY Passive Cell Phone Amplifier

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