Lately I've been working on a few analog audio circuits. I was sitting around admiring my finely soldered boards (sarcasm) and thought, "Hey! Why don't I put this crap in a box or something?" I looked around the house, but alas, there were no box-like objects to be found. I then proceeded to destroy my garage, and Voila! I found an old hollow book box, and this project was born.
You can pretty much do this entire project with the following items:
Soldering Iron and Solder
Hot Glue Gun
Drill (optional but handy)
Hollow Book Box (I got mine at a junk store, but you can buy an ugly version here )
4-8 ohm 4" Speaker (I got mine from an old police radio attachment)
Speaker cover (left over from a car stereo install)
9-volt battery x2
1M x3 ohm
2.2k ohm(if using a power led)
3.3uf (I used a 4.7 because I couldn't find a 3.3)
25 ohm Rheostat
5k Linear pot
100k audio taper
The components listed above will make the following boards (which I'll explain how to make):
Little Gem Amp Circuit (http://www.runoffgroove.com/littlegem.html )
Mini-Booster Effects Pedal (http://www.muzique.com/tech/miniboo1.htm )
Step 1: Circuitry!
The basis of this amp is two simple audio circuits.
*Remember that it's always easier to breadboard a circuit first. On audio circuits you can exchange capacitor size values for different tonal and reactive effects*
First, assemble the mini-booster schematic found (here ).
Below you'll see that I've posted the vero board layout for both. I'm sure my layout isn't the most efficient or compressed, but it does work. Make sure that you leave yourself plenty of wire on all your external leads. This will be handy for moving the boards around inside the hollow book.
Next, assemble the "Little Gem" schematic. This is the simpler of the two circuits. You can look (here ) for more information.
*note* On my veroboard layout below, you'll notice some red scribbley lines. This indicates where you need to sever the trace on the board. You can also test each individual circuit since they are individually powered.
After the assembly of both circuits, simply attach the output of the mini-booster to the input of the little gem. You can cut the ground wire from your 9v batteries and attach both ends to an On/Off switch (pictured below) The two battery grounds to the 'OFF' and the two board grounds to the 'ON' of the switch.
The complete circuit can be found (here ).
*Note on the Pots* The 25 ohm Rheostat acts as a volume control (knob 1), while the other to pots act as gain controls for the individual circuits.
Step 2: The Finish Work
After assembling your circuits, all that's left is to drill some holes in your book! I used a cup to trace about a 4" hole, and then cut a series of lines with a box knife. I then used a dremel tool to sand the sides of the hole, and widened it to the point that my speaker would fit. I used drill bits for the volume pots, guitar input, and the on/off switch. I would have been smarter if i would have used velcro to hold the batteries in place....but i'm not....so I didn't. Cram everything else in, and BAMMO! Amp in a book.
Way to go, Starfox.