Introduction: The Process of Building a Cigar Box Guitar Amp - Little Gem or the $5 Crackerbox Amp

Picture of The Process of Building a Cigar Box Guitar Amp - Little Gem or the $5 Crackerbox Amp

I have been an electronics hobbiest for several years, and there is something special about making musical toys. The most fun that I have is making Cigar Box Amps to sell locally, on Etsy.com, and sometimes eBay. I also run a website, tech-tut.com, that I try my best to describe what I'm doing and building. I'm finally attempting a highly detailed process that I can't exactly publish on my site, so here I am on Instructables. This is my first Instructable ever, and I value any feedback to make it the best it can be.

Building a Cigar Box Guitar Amp is not difficult, but it can be time consuming, especially if you want it to be near-perfect. Some things that don't always work out for me are the hole diameters and the occasional scratch in the soft wood of the cigar boxes. Even some of the nicer, tougher cigar boxes give way easily if your fingernail slides across the grains.

The time frame to complete a Cigar Box Amp ranges from a little over an hour to four hours depending on whether you have an assembly line or not. It also depends on the cigar box. If you have a thin box, it won't take you as long. Thick wooden boxes take longer to file the holes (unless you have potentiometers and jacks with long threads).

Overall, you will enjoy your Cigar Box Amp. Whether you buy one pre-assembled or built it from scratch in your favorite cigar box, you can expect that people will be impressed.

Step 1: Gather the Necessary Parts

Picture of Gather the Necessary Parts

This is the toughest part. You need to decide what you want to install your amplifier in. The easy choice for me is to use a cigar box, but Make magazine ran an article that used cracker boxes.

Next, you need to go shopping for parts. There are kits that you can buy with nice printed circuit boards out there. I've never used one because I like the "from scratch" method.

These are the parts from my latest Jameco.com order:

Quantitiy---Part Number----------Description
1-------------24133-------------------LM386-3 700mw opamp
1-------------140514-----------------100 ohm pot
1-------------29197-------------------5k ohm pot
1-------------281746-----------------stereo Switchcraft 1/4" jack
2-------------102788-----------------chickenhead knobs 
1-------------2006764----------------5mm blue LED (Everyone likes blue, right?)
1-------------23077--------------------5mm LED holder
1-------------216452------------------Battery snap
1-------------1954818----------------speaker, 4-inch, 5w
1-------------690380------------------10ohm resistor (has to be bought in qty 100)
1-------------690865------------------1k ohm resistor for LED
1-------------1947351----------------.047uF capacitor
1-------------15229--------------------.01uF capacitor
1-------------30496--------------------220uF Electrolytic capacitor
1-------------93761--------------------100uF Electrolytic capacitor
1-------------151590-------------------voltage jack
1-------------43140---------------------perfboard or other circuit board
Grill cloth (Optional...find scraps of fabric locally) 

Wire, solder, soldering iron, wire strippers, wet sponge, spray glue, hot glue gun, hot glue sticks, sand paper (220 grit works fine), rotary cutoff tool, drill and bits, hole saw (3-3.5"), drill press (optional), files, pliers, tape measure, calipers (optional), pencil.

The original circuit was labeled the "$5 Crackerbox Amp" in Make Magazine volume 9, but the parts order above is just under $30 buying the minimum quantities. You still have to find a cigar box and pay for shipping. :)

You may be able to find some of the above parts cheaper locally. Half the fun is shopping around for parts. 

Step 2: Drill and Sand Your Enclosure

Picture of Drill and Sand Your Enclosure

Your Cigar Box Guitar Amp is about to be born.

I'm going to describe my method using an imaginary 7"L x 7"H x 2.5"D cigar box. These dimensions won't exactly match the photos. Every cigar box is different, and the measurements that I make will not be the same.

Do a dry layout! Make sire that the parts will fit the cigar box.You also want to make sure that the controls and parts do not interfere with the closing of the cigar box.

I always start with the speaker location and work my way from there. I like to have the speaker at the "bottom" of the amp like most traditional, store bought amps. We are using a 4" speaker, so the center of the speaker is 2" from any edge. We will mount the speaker with the center 2.5" from the bottom of the cigar box (Be sure to factor in the thickness of the box side wood and add that to the measurement). The thickness of the wood on my imaginary box is .25", so I am going to make a dot at 2.75" (Measurement A in my drawing). Then find the center of your box. The center of my imaginary cigar box is 3.5" (Measurement B in my drawing). If the bottom left of the cigar box is the origin of an xy plane, the xy coordinates for this hole would be (3.5",2.75"). Use a punch or the tip of your pencil to bore a small divot so that your drill doesn't travel. Using a hole saw, drill a hole here.

The next holes to drill are for the LED, potentiometers, input jack, and voltage jack. In the drawing I have everything but the voltage jack on the "front" of the cigar box. I usually call the actual bottom of the cigar box the front. I evenly space them across the top edge of the front. Each hole is 1.4" (about 1 7/16") from each other. The outside holes are 1.4" from the edge. These holes are 1 - 1.5" from the top of the amp. You can be creative and put your parts wherever you'd like.

The final part to be drilled for is the power jack. You can put it on the side. Simply center it and drill wherever you please. Again, every cigar box is different, and giving you an exact measurement probably wouldn't work. For my imaginary cigar box, I will drill a hole that is at (3.5",1.25") with the corner of the side being drilled as the origin. 

Drill each hole so that the parts fit using various drill bits. I use a stepper bit and then file the hole with a round file to get the final diameter. Dry fit all of these parts before continuing. Once the parts fit into their holes, sand the speaker hole so that it looks nice.Start heating up your glue gun!

Note: Be careful not to sand the outside of the cigar box. You only want to knock off the burrs left from the drilling process.

Step 3: Install the Speaker and Controls Into the Cigar Box

Picture of Install the Speaker and Controls Into the Cigar Box

Dry fit all of the parts one more time before continuing. Visually inspect the box to make sure that the lid will close. If everything acts like it's going to fit, then set everything aside except for the box and the speaker.

If you choose to use a speaker cloth, now is the time to attach it. Spray a layer of glue inside the enclosure around the speaker hole. Cut a circle of cloth, and place it over the hole (on the inside of the box). Stretch it out so that it dries tight.

Next, put some hot glue on the corners of the speaker frame (on the speaker cone side) [Be sure not to get any glue on the speaker!], and press it to the box. Once it cools for a few seconds, apply more glue to the corners to get a good bond to the box. Once this glue cools, your speaker should not move.

Next, insert your potentiometers and tighten the nuts. Use a rotary cutoff tool to trim the 100 ohm trim pot shaft. It is too long. Insert your input jack and the voltage jack, and tighten the nuts. Finally, press in the LED holder. Insert the LED from the inside, and hot glue the LED into place.

Now, you are ready to make the circuit.

Step 4: Time to Make the Circuit and Connections

Picture of Time to Make the Circuit and Connections

First, you'll need the schematic and layout. http://runoffgroove.com/littlegem.html

Start by placing the LM386-3 into the perfboard. Then populate and solder the parts around it in accordance with the schematic and the wiring diagrams. My drawing below shows you pretty much what connects to where.

Then follow the wiring diagram that I published on my website Adding a power supply to a Cigar Box Amp (REVISED) or the one at GeneralGuitarGadgets. Looking at both will provide some insight into the wiring of these circuits. I also drew a picture to give one more view to the wiring diagram and layout. The drawing below is exactly how I install my circuits.

If you want a printed circuit board, GeneralGuitarGadgets.com has one for $8. That's a little steep for me since I can populate and solder a circuit onto perfboard in under ten minutes. It's the wire connecting that will take a little longer. They do sell a 9v regulated power supply for $11 that is worth having.

After you solder the circuit board together you can make the individual connections to the controls. Following the various wiring diagrams that I've linked to should make it fairly easy.

[I feel as though this is cheating you! After publishing I realized that figuring out the wiring is still tricky! The next set of instructions is going to be full of step by step photos.]

Step 5: Step by Step Photos of the Installation (Wiring Diagram in Real Life)

Picture of Step by Step Photos of the Installation (Wiring Diagram in Real Life)

The colors that you use to make this circuit don't really matter, but I am going to describe the colors to help make following this process a little easier.

Picture 1: The first step is to solder the negative battery wire (A) and a long black wire (B) to the tip terminal of the voltage jack.

Picture 2: Solder the positive battery wire (C) to the contact terminal of the voltage jack.

Picture 3: Solder a long red wire (D) to the sleeve terminal of the voltage jack.

Picture 4: Solder the long black wire (B) from picture 2 to the sleeve contact terminal.

Picture 5: Solder a 1k resistor to the LED's cathode. This is the end with the small indentation.

Picture 6: Solder a long black wire (E) to the other side of the 1k resistor.

Picture 7: Trim the long black wire (E) from picture 6 to the third terminal of the 100 ohm pot. Then solder two long black wires (F and G) to the same contact. Take notice of the pot's orientation.

Picture 8: Solder a blue wire (H) to the positive terminal of the speaker.

Picture 9: Solder the other end of the blue wire (H) from picture 8 to the middle terminal of the 100 ohm pot.

Picture 10: Solder a long green wire (I) to the first terminal of the 100 ohm pot.

Picture 11: Solder  the long red wire (D) from picture 3 to the anode of the LED. Then solder another long red wire (J) to the same spot.

Picture 12: Solder the other end of the black wire (F) from picture 7 and another long black wire (K) to the negative speaker terminal. Next, solder the other end of the long black wire (K) to the ring terminal of the input jack. Finally, solder a long yellow wire (L) to the tip terminal of the input jack.

Picture 13: Solder a wire (M and N) to pins 1 and 3 of the LM386-3 IC.

Picture 14: Solder the white wires from picture 13 to the terminals of the 5k ohm pot. Solder wire (N) to the right terminal, and solder wire (M) to both the middle and left terminals.

Picture 15: Solder the long yellow wire (L) from picture 12 to the .01uF capacitor on the circuit board.

Picture 16: Solder the other end of the long green wire (I) from picture 10 to the negative end of the 220uF capacitor.

Picture 17: Solder the other end of the long red wire (J) from picture 11 to pin 6 of the LM386.

Picture 18: Solder the long black wire (G) from picture 7 to pins 3 and 4 of the LM386.

At this point, all of the wires should have a home.The next step should really make you happy.




Step 6: Finishing Up

Picture of Finishing Up


Connect a battery to the battery snap, and plug in a guitar. The LED should light up.

If the LED lights, turn the volume and gain all the way up and play something. Does it sound right? Play with the volume knobs and make sure they work correctly. If it sounds great, then put a dab of hot glue on the circuit board, and glue it down so it doesn't flop around.

I used a piece of magnet wire to tie up the wires coming from inside the box to the lid.


Step 7: Plug It in and Play

Picture of Plug It in and Play
By this point you should have a working amp.

You can add features like handles and decorations at this point. Search Google for cigar box amp photos. Join CigarBoxNation.com, and chat with other cigar box hackers. The Cigar Box Amp is just the beginning.

This is a video of me demonstrating my first 3/4w Cigar Box Guitar Amp. You can also check Etsy.com if you have decided that pre-made is the route for you.

Comments

XxBiohazardxX (author)2011-09-04

awesome....but, can I use other model of Jack DC? for example this...

tech-tut (author)XxBiohazardxX2011-09-05

Yes. Any DC jack is fine. If you have three contacts they will fit perfectly wihout any modifications.

SheinnaF (author)tech-tut2017-02-10

what modifications should i do if i will use a mono jack ?

phoxfire5 (author)2016-01-11

What's the biggest, highest watt/ohm speaker this thing can drive? And how would one increase the capacity for such? I have an old italian wine box, and it can fit a ten incher.

ArthurJ5 (author)phoxfire52016-12-04

Size doesn't matter. You could drive a Marshall stack with this amp, it won't get loud though. This amp will drive any 8 ohm loudspeaker, but it will only output 3/4 of a watt. So, what you are looking for in a speaker is lots of decibels per watt. Look for a high efficiency speaker one that puts out 95-100db per watt. Whether you use a 5 watt or 50 watt speaker with this amp simply won't matter.

If, on the other hand, you want to increase the power output of the amp I suggest you look at other projects. This little amp really can't be modified for higher output.

phoxfire5 (author)phoxfire52016-01-11

Also yes I realize this is a very old post and I realize I may not get an answer, but I'm hoping :3

GabrielS7 (author)2014-11-05

Worked perfectly!! The only problem is that it's making a lot of static noise. I believe is because I didn't ground it properly, how can I ground the board??

Shwephioo (author)GabrielS72015-10-26

U can solve it by making your circuit as short as u can.

robert.carlson.3304 (author)2015-04-10

Thanks, just purchased an e book from amazon and this is better than that.

runolorun (author)2015-02-14

Hello, the used pots are linear or logarithmic?

sbrittain3 (author)2014-09-04

The link didn't work is this the one? http://www.jameco.com/webapp/wcs/stores/servlet/P...

Thank you Tech-Tut for your help I assume I wire it the same way correct Thanks again.

tech-tut (author)sbrittain32014-09-04

Shoot. After a few clicks your link worked. Yes, that will do fine.

sbrittain3 (author)tech-tut2014-09-04

Thank you so much Tech you are awesome. So sorry I didn't see this reply I just asked about another lot they appear the same. You have saved me a lot of money and helped out greatly. Thanks again for your kindness in helping me

tech-tut (author)sbrittain32014-09-04

Absolutely. If you need assistance, you can contact me directly: robbie <at> tech-tut.com

God bless ya.

sbrittain3 (author)tech-tut2014-09-04

Will this work too just different solder points?

sbrittain3 (author)sbrittain32014-09-04

Links aren't working ugh.

tech-tut (author)sbrittain32014-09-04

Links don't seem to be working. Here's the Jameco part number: 255485
Manufacturer part number: RV24AF-10-15R1-B13

It's a $1.55 pot. In quantity of ten you can get it for $13.90USD.

Hope this helps!

sbrittain3 (author)2014-09-03

Is that a 100k ohm A potentiometer or B I know this is old hoping for answer. Thanks

tech-tut (author)sbrittain32014-09-04

You could check eBay for alternatives. Anything from 100 ohms to 1000 ohms would probably work. Look for some lots on there.
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_255477_-1
Hope this helps. The 1k are about half the cost of the 100 ohms.

tech-tut (author)sbrittain32014-09-04

It is a 100 ohm linear pot. Here's the datasheet from Jameco.com

http://www.jameco.com/Jameco/Products/ProdDS/140514.pdf

sbrittain3 (author)tech-tut2014-09-04

Thank you very much I appreciate it. Do you know where I can get it in bulk for a very good price? I am doing these amps for giveaways to soldiers overseas and cost is a factor. I am disabled and trying to give back to our boys and girls still there. I am limited on funds. Up until now I have been making them with the gain only but want to add a volume pot to make it a little nicer. Thanks again

ThumperCastle (author)2014-04-06

I'm having trouble trying to find the 5W rotary potentiometer in the UK. I'm using the Farnell website (RS Components doesn't seem to have anything here). The closest I can find are 3W, but they cost about £15 each (approx. $20), which doesn't seem right. How much effect would a 3W have on the rest of the circuit? There are also some 6W ones. And some are available with different resistances.

tech-tut (author)ThumperCastle2014-04-06

You don't need a high watt pot. Look for 1/2 watt.

BurningBlades (author)2013-11-04

Dude, do you know how hard it's been to find an amp instructible on this site that actually goes into detail about the wiring instead of just posting a link to the little gem site? Thanks for this, it's really helpful.

justasking (author)2013-05-19

I want to ask about the Voltage for 0.1 & 0.47 capacitors? Can i use LM386 N1 in cigar box amp? Im hoping for your response. Thank you.

celtictrinityknot (author)2013-01-15

Can I leave the voltage jack out if I dont want to use a wall wart, or does the circuit still need it? I just want the amp to turn on when the cord is plugged in instead of the battery. thanks!

tentwistle (author)2011-11-21

can anyone tell me what a voltage jack is, what its for and where to get one please?

lentzell (author)2011-10-02

Great job, man, but really, the star in the video is your kid. A lot of fun. Mine were that little not long ago...

jmantelli (author)2011-09-20

This is the best instructions Ive seen for this!going to try my hand at this one this weekend for my cbg! Did you fix the drawing? As someone mention the drawing inputs were wrong but picture was right???

tech-tut (author)jmantelli2011-09-20

I only reference the schematic from http://runoffgroove.com/littlegem.html. I've built about 30 amps using these very steps with no issues. If the exact link to the schematic in question can be supplied I'll be happy to look at it if it was something that I created.

If you run into issues I can be contacted at 'robbie [ at ] tech-tut.com'. I usually answer back quickly (within 2 hours) if it is a question I can answer.

boekamp87 (author)2011-08-19

Forgot to add a pic of my build.

boekamp87 (author)2011-08-19

This was a fun build, thanks. I made a Heineken Mini-keg amp out of it.

Only thing, I think your hand drawn schematic might be wrong--specifically the input section. I did it completely to the schematic, and the unit worked but the speaker (a decent one) sounded awful. So I desoldered everything and went by your picture instead (really just switched the position of a few wires on the input) and it works perfectly now.

Anyway, thanks again. My build came out great and I'd have never figured this stuff out myself.

andrezfen (author)2011-07-30

mine is here too..

pquin3 (author)2011-03-14

Okay, cool, that was a fun build, kind of like figuring out a code, but those electronics are REEELY SMALL! Love it with my CBG, but I can't say its working exactly right yet, and I'm not an electronics wizard at all. Problem is, with the gain turned down, I get almost no volume, even with the volume turned all the way up. With the gain turned even a little up (say 25%) the feedback is really over the top. So what say you, electronics wizards? Did I screw up the circuitry? Could it be the Piezo pickup? Would a solenoid pickup work better? Or is this the consequence of wandering around blind without really knowing what I'm doing?

chuckw68 (author)2011-03-01

I just finnished mine.You can see it on my You Tube channel. seach chuckwier on You Tube.
It was fun and easy to build. I have no electonics expirence. This was a great instructable.

dirtyroger (author)2010-10-11

Well this is an amazing build, its gonna have to be my new project after i've finsihed my CBG.

I've started a blog for my first CBG build here dirtyguitarguide.com

radiorahim (author)2010-08-22

Cool. I'm glad you decided to use a 4" speaker for the second one, I was going to say the 2" speaker was too small. I made a cigar box amplifier too. I didn't have a hole saw or access to a jig saw so I had to trace the hole with a 1/4 drill bit and join the individual holes together. I'll upload some pics soon.

radiorahim (author)radiorahim2010-09-19

Here's mine.

F-17 (author)2010-08-16

Thats pretty Cool man, its like one of those tiny clip on amps

About This Instructable

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Bio: I am a college student studying Electronics Technology. Someday, perhaps when I grow up, I hope to be an engineer.
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