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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:

Tools: 

Soldering Iron and Solder
Dremel Tool
Box Knife
Hot Glue Gun
Drill (optional but handy)

Components:

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

Electrical Components:

Resistors:
2.2M ohm
1M  x3 ohm
1k ohm
100 ohm
2.2k ohm(if using a power led) 
10 ohm

Capacitors:
0.047uf  x2
10pf
10uf
3.3uf (I used a 4.7 because I couldn't find a 3.3)
0.22uf
100uf  x2
220uf
0.01uf

Other:
LM386 
MPF102  x2
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 )
      and
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

Those with weak constitutions should probably look away!  (Because my hot glue work is horrendous)

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.



This is for sale btw.  Message me.  :)
<p>Wow soooo cool.</p>
Great tut!!!<br>I've always loved the Little Gem--you should hear it drive one of my 4x12 cabs. Yes, you read that right!<br>I do have a suggestion. The additional booster circuit is nice, but unnecessary. <br>If you guys have electronics experience--GO FOR IT.<br>But, if you use the LM386-N IC...you just eliminated the need for it. The 386-N puts out about .75 watts RMS, as opposed to the .5 watt typical LM386.<br>What I usually do when building one for a client or friend, is add a tone stack and switchable clipping diodes. <br>The tone stack adds a basic EQ as found on other amps--depending upon the tone stack you build. For noobs--start with the BMP stack.<br>When you get to know your way around a soldering iron--move up to 3-knob tone stacks.<br>For the clipping diodes, that just adds diffetent distortion flavors. Just do a little research.
Can this be done with a real book? <br>(in terms of conductivity, heat, fire safety, etc)
Yes--after you &quot;hollow out&quot; the pages, here's what to do:<br>Get some good wood glue (Titebond works great), and apply a light coating to the &quot;walls&quot; of the hollow pages. Let dry overnight. This secures the pages from flapping around and also gives you a solid and semi-smooth surface for the following steps.<br><br>The circuit will not set fire to the paper. It's always good practice to secure your battery with a clip, but if you don't--at least wrap it in a layer of foam.
would it be possible to substitute the rheostat for another (linear) pot?
Not with good results. Radio Shack carries the rheostat, as well as Mouser, Jameco and Digikey.<br>Always read the IC datasheets for specs and circuit examples--they explain everything you need to know.
very well done. Clean, I would say (:
Finally, a true audio book!
This is brilliant.
This is sexy. And a classic book choice.
You're sexy! haha
This is Awesome!!!
Thanks so much!
The links to little gem amp circuit and mini-boost effects pedal are the same.<br><br>The writing that is linked gives the correct addresses, but both of the hyperlinks are to the mini-boost effects pedal.<br><br>Good instructable although i would like a little more description about assembling the circuits- what all the pots do etc. because there is almost a little too much information at those linked sites for beginners like me, although i did quite a lot of research into mini amp circuits when i wanted to build one earlier this year.
Whoops! I'll fix the link and add some more detail. I just got impatient with my posting, haha. Should be up later today.

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