Electric Cigar-Box Guitar W/ Built in Amplifier

I was tired of carrying around heavy guitars and amplifiers whenever I went on holiday or camping and needed something to play while I was away. That's why I made this. This is a light, portable, strat-style guitar that I take with me whenever I go away from home and want a guitar with me. It has two built-in speakers that, while certainly not loud enough to perform with, are definitely loud enough to practice with and can match the volume of an acoustic guitar, but with the tone and sound of a stratocaster. This project cost me £80 in total to build, cost of tools not included, and uses an amp circuit designed by the good folks over at 'runoffgroove'. It's called the RubyAmp, and is easy and cheap to make and gives a nice, crunchy, Fender-ish tone. I also included an output socket so that I can flick the inbuilt amp off and plug it into a proper amplifier for performances.

And I know that having pickups and an amp circuit in such close proximity isn't ideal, but this is just something for practising. I've noticed that, since I put the amp circuit in the top left, at high gain the neck pickup starts squealing since it's so close to the amp circuit. This isn't much of a problem though, and the other pickups are fine. Also, since the box is stuffed with electronics and I used electric strings instead of acoustic, this CBG doesn't sound great acoustically. But that's not a problem when the amp circuit is flicked on. It just means that if the battery goes dead I'm stuck with a quiet-sounding guitar until I can pick up another 9v battery.

The biggest challenge was designing something that could withstand the tension of the 6 strings, as the cigar box itself is very flimsy. I used a strat neck from Ebay as I really didn't want to build a neck, and designed the structure so that none of the tension is on the flimsy box.

This is a great project for someone getting into electronics, soldering and basic woodworking. It's actually pretty easy to make and the result is very satisfying and impressive. Don't be intimidated by the thought of building a neck, just buy one like I did. They come pretty cheap.

Take into account that you'll need to use some initiative to make one of your own. I can't provide dimensions of the parts you need to cut out or the size of holes or anything because this all really depends on your individual cigar box, guitar parts and taste. But read on to find out how I made mine, and apply it to your own cigar box!

Step 1: What You'll Need

I used Ebay to buy all the parts for the guitar itself. For the components for the amp circuit, I used Bitsbox.com (UK). In the USA I'm sure that something like Radioshack would be fine. I salvaged the speakers from a pair of computer speakers I had lying around. Don't go out and buy expensive speakers for this, look around and see what you can find. If you can't find anything suitable, get some cheaper second-hand speakers. It's not really worth putting a really expensive, high-quality speaker into this.

Parts list:

Guitar neck - I used an unfinished strat neck with an unfinished headstock, as you can see above (the headstock hasn't been cut out yet. Make sure that it has a truss rod, which can be used to adjust the angle of the neck.
Pickups - You can get pickups of your choosing. If you want something easy and simple like me get a pre-wired pickguard, or a pickup kit. I went for strat-style, but tele style and other pickup configurations are fine too. If you want to shell out for expensive pups (pickups) go right ahead, but I just went for cheap, unbranded ones. For me, this guitar is for practice while on holiday so it doesn't need to be amazing. diydonut has found pre-wired pickup sets for cheap on Amazon.
Bridge - Now I went for a tremolo bridge, which has a whammy bar/vibrato bar. Basically, only the front end of the bridge is actually connected, the back end is held down by springs. You can push on the whammy bar to bend the notes and do vibrato. There's a demonstration of this at the end of the video. This makes it more fun to play, but is significantly more difficult to put together. It took me a long time to fit it in place. Go for a fixed bridge if you want something simple, but don't be afraid of attempting to put a tremolo bridge in place, it's a nice challenge.
Potentiometers for the pickups - If you get a pre-wired pickguard or a pickup kit these should come with it. Potentiometers are the dials for tone and volume. And if you have multiple pickups like me you'll need a pickup selector too. If you decide to go for a kit or pre-wired guard, don't worry getting these, but bear in mind if you get individual pickups that you may have to get some pots and a pickup selector.
Cigar box - I got mine for free from a tobacco store. Doesn't have to be a cigar box, see what you can find.
Strings - get electric guitar strings, not acoustic strings, they're lighter.
Springs - get the right ones, look for 'tremolo bridge springs', they should come with the bridge though

Parts for the amp circuit:

If you've never built a circuit before, don't worry, this is really easy and I'll guide you through it.

LM386 IC - make sure you get the right one
9v battery
MPF102 or 2N5457 or J201 transistor
100 uF capacitor - get non-polarised ones if you can so you don't have to worry about which way round to put them. This applies to the other capacitors
220 uF capacitor
2 x 47n capacitor
100n capacitor
1.5M resistor - same as 1M5
3.9k resistor - same as 3k9
10 ohm resistor - sometimes written 10r
10k potentiometer (linear) - for the volume dial
1k potentiometer (linear) - for the gain dial
2 x pot caps - choose ones that you like the look of, these are plastic dials that go on the pots
1 x switch - again, get one that you like the look of
Wires - get a bundle of wires
A mono 6.5mm socket
9v battery clip

Tools

Drill - fairly essential
Some sort of power sander - I use a sheet sander - optional, but takes less effort than filing
Files - very useful
Dremel - extremely useful, versatile tool. Not essential but I would highly recommend it
Coping saw - essential, especially for cutting holes in the cigar box
Vice/clamps - essential
Soldering iron - essential
Screwdriver
Multimeter - useful

If you do go with a pre-wired pickup set then make sure to take a picture of it! This is useful if you need to lengthen some of the wires or re-solder anything.

My speakers faced down, they wouldn't fit any other way but have yours facing up if you can.

Step 2: Overall Design

Before even starting your guitar, think through exactly what you're going to make. I'll go though my design. It's useful to have all of the necessary parts at hand for measuring.

My design, pictured above, focuses on keeping the string tension away from the cigar box, which would definitely not be able to withstand the tension. It also uses a pre-made guitar neck off Ebay. Basically, the neck bolts onto a piece of wood that runs through the box where it is connected to the bridge through the box lid. As shown above, an extra piece of wood with a hole for the bridge pickup is bolted onto the length of wood to give the height required to meet the lid of the box. For the tremolo system to work, a channel has to be dremelled out of the main length of wood to fit the springs.

This structure is able to withstand the string and spring tension fine, and the box doesn't take any of it.

Study the images above, measure out your box and design something similar.

Important - The placement of the bridge (where the end of the strings attach) is very important. It needs to be in the right place so that the scale length is correct. If it is too far forwards or backwards, the guitar will not play in tune. Generally, the bridge should be twice the distance from the nut to the 12th fret. The nut is at the top of the neck and the 12th fret is where the two dots are.

Go ahead and saw out the main piece of wood. It should be protrude from the edge of the box and go up to the start of the bridge if you're using a tremolo bridge. If your bridge is fixed it should go underneath the whole bridge. Don't worry about making it perfect, this is just a prototype so that you know where and how everything fits.

Picture 5 is just to show how the tremolo bridge works - this isn't how I built it

Step 3: Making Holes in the Cigar Box

You now need to make holes for the pickups, potentiometers, strap nuts, bridge, neck, output jack and sound holes.

I did the pickup holes first. Since I bought a pre-wired pickguard I could lay the pickguard over the cigar box and trace out the positions of the pickups. If you don't have a pickguard you can easily find templates online. Be careful when making the holes, you don't want to make a wrong move and put a hole in the box where there shouldn't be one. To make the pickup holes, I drilled a hole big enough for the coping saw to get in through, inserted the coping saw by taking the blade off then re-attaching the blade through the box, sawing out the hole then filing/sanding the hole down. Drill two holes either side for the pickup screws.

The holes for the pots could just be drilled. Remember to drill small holes for the little extrusion on the pot to fit into. I had to widen the top of the pot holes so that the hex nut would actually fit onto the pot to secure it in place. Drill holes for the switches, the output jack and the strap nuts in the same way. There should be one strap nut on the bottom of the box and one on the left of the top surface where the neck goes in.

I made the channel for the pickup selector by drilling a series of small holes and filing them into a single channel.

The hole for the bridge must be smaller that the bridge itself. For a tremolo bridge, it only needs to be big enough so that the part that extends downwards from the bridge can rock back and forth freely.

Don't worry about the neck hole being perfect, there needs to be a little room so that the lid can be opened and closed once the neck has been attached. It should be slightly less deep than the depth of the wood plus the depth of the neck.

Make sure that there are sound holes. I actually forgot to do them and had to add them at the end. You can do anything you like, f holes look quite good. You can find templates online. The last picture shows the sound holes at the bottom of my box.

Step 4: Cutting the Headstock

Fairly simple. Print off a template of your choosing and cut around it.

When attaching the machine heads, make sure that you don't tighten the screw too tightly as the head can snap off.

Step 5: The Amp Circuit

Sorry that I don't have many pictures for this.

The amp circuit I use is designed by runoffgroove, here's a link:

http://www.runoffgroove.com/ruby.html

It's a great little amplifier run off a 9v battery with a volume and tone control, plus it's really easy to build. If this is your first time reading a schematic don't get disheartened, it's actually pretty simple.

The symbol with the 3 horizontal lines means 'ground', and all of the grounds are connected together. It's just more convenient to use the symbol than to draw lines to them all. The negative battery terminal is also connected to ground, and the negative terminals of the input jack and the speakers are connected to ground.

You don't have to worry about actually understanding the schematic too much, you just have to be able to solder the components onto a stripboard. A stripboard has strips off copper underneath running from left to right. Here's a link to a nice, compact stripboard layout:

http://www.paulinthelab.com/2014/07/ruby-amplifier...

The red squares mean that the copper strip has to be broken at that point. I just use a drill and make an indentation so that the copper no longer touches. Have a look at the picture above. To make sure that you do it right take a multimeter, set it to measure resistance and touch it on either side of the indentation. If the figure is 1, you did it right. If it's less than 1, you need to drill more.

The blue lines mean that wires have to be put onto the board. I use chopped-off resistor legs for this. Just solder them in after you've drilled the indentations.

Next solder in the LM386, then the resistors, then the capacitors and the transistor.

On this stripboard, a wire needs to be soldered to each of the holes on the left and two of the holes on the right. The 'GND' is ground, VR1 refers to the volume pot and VR2 refers to the gain pot. VR1-1 means that a wire has to go from that hole to the 1st pin of the volume pot. Notice that two of the gain pots are connected (VR2-1,2). You can use a resistor leg to connect them. You should be able to find datasheets for your pots which tell you which pin is which number.

Put a switch in between the positive terminal of the battery and the '9V' hole on the stripboard.

Whether you wired your pickups yourself or you have pre-wired pickups, there should be a positive and negative wire coming from the pickup/pot assembly. The positive wire should be attached to both the output socket (see below) and the 'IN' hole on the stripboard and the negative wire should be attached to ground. There may be an extra grounding wire which you can just solder to the bridge/spring assembly later.

Note that in pre-wired setups, anything soldered to the casing of a pot is ground.

Your salvaged speakers should have a positive and negative terminal. Solder the positive speaker wire to the 'Out speaker+' hole on the stripboard. Then connect the negative speaker wire to ground.

The output socket has a positive tip and a negative sleeve. Follow the tip down to the positive lug and solder the positive pickup wire to it. The sleeve lug can be soldered to ground.

Once you're done, you can test if it works by hooking up a 9v battery and touching the round metal part of a pickup gently. If everything's correct, you should here a pop from the speakers. Bear in mind that only the pickup selected by the pickup selector will do this, so make sure to test all pickups by moving the pickup selector as you test them. Also, if you don't hear anything, make sure that all the pots are turned all the way up.

If it all works go ahead and attach everything to the inside of the box. I made sure that I used more wire than needed so that the wooden assembly could easily be fitted in.

When attaching the pickups, technically there should be springs in between the box lid and the pickups, however, I needed to raise the pickups more to be closer to the strings so I left them out. You'll have to experiment.

Step 6: Putting It All Together

First, check that the smaller piece of wood fits around the bridge pickup. Adjust as necessary, then attach it to the longer piece of wood. Be careful not to split the wood when drilling. There's also a thing square of wood underneath for the springs to attach to.

No pictures of this sorry, but mark out 6 holes in the lid for the 6 bridge screws to go into, and drill them.

Fit the wooden assembly into the box, leaving enough for the neck to attach to, then drill the bridge into place. Make sure that it is centred.

Step 7: Attaching the Neck

Pretty easy but it is vital that the neck goes on straight. Measure carefully, and drill the neck in. Make sure to remember to include the metal back plate. I had to make a couple of holes in the box to drill the bottom two screws in.

Step 8: Attaching Strings and Springs

This part is fiddly. I found that 2 springs was enough to hold the bridge in place. I attached one spring, wound up 3 strings, then attached the other spring, then the last 3 strings.

To attach the strings, first feed them through the bottom of the bridge then wind them into the machine heads. Make sure that you put the right ones in the right places. They go from thinnest to thickest, right to left (bottom to top).

I attached the springs by hooking the loop onto the metal plate then stretching the hook into the bridge-hole with a pair of pliers.

You may have to deepen the channel you made for the springs if they don't stay in.

Remember to attach the string retainers, shown above, as you wind up the last 4 strings.

Tune them up. It may take a little time to break them in, as an equilibrium between string and spring tension has to be reached.

Adjust the saddle height first with an alan/hex key. Make the strings sit fairly low over the fingerboard.

Next, tighten the pickup screws to bring them up so that they're close to the strings.

Finally, if necessary, tighten up the truss rod to adjust the neck.

To improve intonation, you can move the saddles back and forward with a screwdriver. If the 12th fret is sharp, move them back by tightening the screw, and vice versa.