I picked up a cheap, wooden jewelry box from a local craft store for around $5 a while back, and it's been collecting dust on my desk ever since. Lately I've grown tired of looking at it and have decided that it's time to do something with it. One of my hobbies is building guitar effects pedals and thought it would be nice to have a small amp for testing purposes in my project room.
The circuit design comes from runoffgroove.com and is a great beginner electronic project. The amp has few parts, is inexpensive, sounds great and has impressive power, considering it runs on a 9V battery. It will even power my 4 x 12" guitar cabinet! (Not at gig levels, but great for practice)
Step 1: Materials and Tools
Wood Jewelry Box
Rubber Feet (4)
Small Piece of burlap or speaker cloth
3" Speakers (2)
Scrap of 1/4" Wood
Paint Brush or Sponge
10 ohm resistor (1)
3.9K resistor (1)
1.5M resistor (1)
1K Linear Potentiometer (1)
10K Linear Potentiometer (1)
MPF102 or 2N5457 Transistor (1)
LM386 or JRC386 IC (1)
.047uF Film or Ceramic Capacitor (2)
.1uF Film or Ceramic Capacitor (1)
100uF Aluminum Electrolytic Capacitor (1)
220uF Aluminum Electrolytic Capacitor (1)
Stereo 1/4" Jack (1)
9v Snaps and Battery Holder (1)
Perf Board (1)
24 Gauge Stranded Wire (1)
Toggle Switch (1)
(Optional) LED and 1K Resistor (1)
Router with Trim Bit
Carving Tools (Rotary tools, CNC, knives, etc)
Step 2: Design
I was inspired by some photos that I saw of some vintage intercom speaker enclosures that had interesting speaker openings. The jewelry box that I have is made out of a light colored wood (Bass wood I think) So I wanted to either paint the box a dark color, or apply a dark-colored veneer and carve though to the light wood to contrast the design.
I took the measurements of the box to use as a template and drew the design in Adobe Illustrator. Here is a link to my vector design if you would like to use it for your own amp project, but please only use it for non-commercial purposes. Thanks!
Step 3: Wood Veneer Application
I got some dark scraps of veneer from a local wood shop (Padauk I believe). Apply a generous amount of hide glue to the box and apply the veneer with care, as it is very fragile. Cover the veneer with a sheet of plastic, as the glue may seap through. Clamp it, or put something heavy on top of it while it dries. (Don't crush it!)
Fun Fact: Hide glue smells like death.
Let the glue dry over night, then trim the excess veneer using a router and trim bit.
Step 4: Filling and Sanding
If there are any cracks or dents, fill them with appropriate-colored wood filler and sand the whole box until completely smooth. It might be easiest to unscrew the hardware on the box while doing this step.
Step 5: Design Application
I carved the design using a CNC machine, but alternatively could be applied with a wood burning iron, carved with rotary tools, good ol' fashioned blades, etc. You could also apply the design using the transfer method outlined in my coffee table instructable.
Step 6: Wood Finish
I wanted to try using Tung Oil on this project, it was easy to apply and I am pleased with the result. Make sure the box is free of dust and apply a generous amount of Tung Oil with a brush. Wait 10-15 minutes and buff with a clean rag. Let dry over night and repeat a second coat the next day.
Step 7: Hardware
I made the speaker baffle out of a scrap of bead board that I found, cut small enough to fit inside of the enclosure. Mount the speakers to the baffle and wrap the front with a scrap burlap or speaker cloth. I didn't have to screw the baffle to the box, because it fit very snugly with the burlap in place.
Next attach the rubber feet. I chose to put them on the side with the hinges, because when the latch is open, the door stays partially ajar, giving the option of having either closed or open-backed cabinet.
Plan and mark the layout of the controls. When drilling, I like to use a bit of painters tape for cleaner holes in the wood.
Step 8: Electronics
Please note that I did not design the circuit in this project, it comes from runoffgroove.com, and is called the "Ruby." You can find the official layouts and information on their website:
I used their veroboard layout. I like to position the components with the wires through the board and bend the leads on the reverse side, so that they stay in place while soldering.
Another helpful resource if generalguitargadgets.com, they have an alternate circuit layout and a very helpful wiring diagram here:
Where to purchase parts
I always tend to buy parts locally if you can find them, here are a couple other suppliers that I have bought from:
Small Bear Electronics: Easy to navigate, fair prices and they have pre-assembled kits available
Mouser: Huge inventory with good prices, sometimes difficult to find what you need due to sheer quantity of products.
Futurlec: Easy to navigate, great bargains, but company is based overseas and could take around a month to arrive.
Step 9: Troubleshooting and Conclusion
Cross your fingers and fire it up... if it doesn't work right away don't worry, go back and trace your connections and make sure that everything is connected properly. Also check your solder joints and make sure that everything looks good. Let me know if you have any questions or suggestions for this instructable. Thank you for reading, go forth and rawk!
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