This instructable is for a cigar box guitar amp, powered by a 9V battery, that I built around the MintyAmp circuit board found on MintyAmps.com. The entire cost was under $30, but could be less depending on what parts you already have laying around.
Step 1: Materials
-1- Cigar Box (mine was about 9x9x2 inches with walls thick enough to stay sturdy) ($3)
-1- MintyAmps Base Model (assembled) from mintyamps.com/store/index.php (7.45 + shipping)
-2- small speakers (mine were about 2.5 inches in diameter taken from a cheap set of computer speakers) ($1)
-1- SPSD on/off toggle switch ($2 or so?)
-1- Volume knob/ potentiometer with as low resistance as possible (free because I already had it)
-1- mono 1/4 inch jack ($2 or so ?)
-1- 9 volt battery connector ($2 for a pack of 5)
-1- 9 volt battery (free with circuit board)
-2- 9 volt battery holders ($1.50 for pack of 2)
- extra wires (free, take them from anything)
Step 2: Tools
-Drill bits in sizes matching that of jack, knob, and switch and a smaller bit for speaker grill
-Soldering iron + Solder
-Hot Glue Gun + Glue that will work on wood
Step 3: Box
You'll want to plan where everything will go in your box before building anything. Make sure that your knob, switch, and jack will have clearance inside the box when the cover is closed and everything is installed. The walls of my box were also a bit thick for the depth of the jack and knob, so you may have to do some counter-sinking to get the nuts to fit onto the threads.
When you have figured out everything's placement, holes can be drilled.
For the speaker grilles, I traced a circle around the speakers, then used a ruler to draw a 1/4 inch grid inside these circles, then drilled a small hole at each intersection of this grid. I don't have any pictures of this but I hope that this description makes some sense. =P
Around this time I also mounted the Battery holders inside the box. I chose to put 2 in so that one can hold a spare battery, since I had extra space anyway.
To attach the speakers to the lid of the box, I put a few dabs of hot glue on the rim of each speaker, stuck them down, and then added more than enough glue all the way around the outside of the speaker.
Step 4: Wiring
If I try to explain the wiring for this I can only imagine I'd end up causing more confusion. =P
The site I purchased the circuit board from, Mintyamps.com has a free downloadable PDF file with schematics, pictures and descriptions explaining how to put together all of the electronics.
I am in no way affiliated with with this site, they were just very helpful and friendly during my purchase from them, and even included a free battery and battery hook-up.
Step 5: Play!
I'm really happy with how my amp came out. The sound is surprisingly good and loud, and the battery life seems to be holding up well. After over an hour of continuous use, I used a battery meter to check the power remaining and it had barely gone down. I plan on buying some rechargeable batteries this week for the amp.
My only problem is with the knob I used. For one thing, it was originally a balance knob from a stereo, so it is backwards (counter-clockwise to turn the volume up). The real problem is that the knob produces zero volume for 90% of it's full rotation and the sound only comes on in the last couple degrees of turning.
I'll probably replace it with a more suited potentiometer and be good.
Thanks for reading and feel free to comment with any questions!