Introduction: Portable Guitar Amplifier

Electric guitars are fun instruments to play and without an amplifier is hard for anyone to hear the sounds coming out of the guitar. Electric guitars provide very unique sounds compared to an acoustic and distortion and tone options make it a more versatile instrument. Unfortunately we don't see much electric guitar playing while camping or in the beach because hauling a guitar amp around is hard and a source of electricity is hard to obtain at such places. 

To remedy the amplification problem a portable amplifier can be build for very little money and effort. This method that will be described here requires no electronic soldering skills, which makes this project very easy to build. The amp will not be build from scratch, instead we will be re-purposing a portable battery powered radio. We can take any battery power radio and modify it. For this project I went to goodwill store and bought a battery power radio that costed $2. If you were to build a portable amplifier from scratch it will cost you $59.99 in parts, and you still have the the assembly. AM/FM radios can be obtained for less than $5 in ebay
If you feel comfortable with a hot glue gun then you should be able to build this project without any trouble. If you do not play the guitar you could build this for someone who does. It is a very inexpensive gift.

If you attempt to recreate this project, please do so with a battery powered radio. You may get killed if you attempt to do this with radio that connects to the house electricity line.

Please read and familiarize your self with all the steps. It would be a shame to stop in the middle and not complete the project. It should take about 4 work hours to complete the project once you have all the tools and parts.

Do you want to hear hear what it sounds like?

Step 1: Items Needed

Here is a list of items needed along with a description.

You will need a battery operated radio. When you purchase the radio make sure it is the type that uses a dial to turn the volume up and down.  You can also modify a wallkman or similar type of cassette player but you will only get sound via headphones, which is great when you want to jam in the middle of the night without disturbing those that are sleeping.

One 1/4" mono jack. This is where the guitar cable will plug into the radio. I recommend you buy the barrel type since it can be screw down onto the plastic. Price is $3.01 for 1 unit at digikey Other places might call this connector a phono plug.

You will need a glue gun and glue sticks. If you're comfortable soldering electronics then you may substitute this with a soldering iron. 

Wire is the last item we need.  Make sure is not very thick a gauge 24 or28 would be nice. 
here is an image giving an idea of the gauge sizes. The bigger the gauge the smaller the wire and vice versa.

Two wires leads with mini alligator clips 

One screw driver, either phillips or flathead. It all depends on the radio you buy.

A knife, a swiss army knife is recommended.

Optional Items:
electric wire striper

Step 2: Tuner or No Tuner.

Okay, so I assume you have the radio with you and you turned it on to make sure it works. Now you must decide whether you want to keep the radio functionality or not. If you decide that you still want to use it as a radio then you will need to tune the radio to a place in the dial where there is no noise. Play with the tuning dial until all you hear is silence. This is very important or you will hear radio noise while playing the guitar, or maybe you want to jam your guitar on top of the radio songs. If you do not care about the radio then later on we will disconnect the antenna rendering the tuning part useless. A switch can be added to connect and disconnect the tuning part, but I'll not be including those instructions this tutorial.

Step 3: Opening the Radio

If you bought an old radio they  are easily serviceable and easy to open. Since I do not know what radio you got then you will be on your own finding and removing the screw to see the internals of the radio. One the radio is open our electronics should be very similar. Be careful while removing the case and make sure no wires get disconnected. 

Step 4: Removing the Radio Signal

If you decided to keep the tuner part skip to step 5.

With you radio open you should be able to locate the anthena part going into the radio. Is a tube witha long wire coil wrapped around the tube. Locate the leads and follow them to where they connect into the board and cut them. After this the radio should be silent and get no more radio noise.

Step 5: Testing Where to Input the Signal

The volume know in the radio is nothing more than a variable resistor, and it goes by the name of potentiometer. The job of that resistor is to reduce how much signal gets passed to the transistor for amplification. It just resists signals. If you wish to know more of how a resistor work see this video.

Notice the ends in the potentiometer? You should have something similar in your radio in the same mount where your volume know is. There is more connectors but the ones we are looking for are the 3 contacts and the ones at the edge is where we will introduce our signal. If they don't work then we will test more points through the radio until you hear sound. Please see the video for demonstration.

Step 6: More Testing

Here is a video of me doing some more testing with my radio. It should aid you if you haven't done this step.

Step 7: Gluing Stuff Into Place.

Now we just need to put everything together. We know where the wires will plug in and we just need to strip the wires and glue or solder them into place. 

Cut about 2 inches of wire and strip about 1/4" from the ends. You need to do this with a second wire. The positive and negative.

Bend the wire out of one of the edges and hook it through the holes of the 1/4" connector and hot glue or solder the wire into place. See img 1.1 above.

On the radio's pontentiometer try to push the exposed wires from underneath the metal tab, and wrap. After wrapping the wire around hot glue or solder the wire into place. See img 2.2 

Step 8: Drilling Holes.

Now that we have everything connected we need to decide what to do with the connector. You can leave it outside and glue the connector externally. However I would recommend that you use the existing antenna hole and and use that as an input.

I used a blade and turned it in circles to widen the antenna hole. Once I was done making the hole big enough for the guitar's plug to fit. I hot glued the 1/4 in the inside of the radio casing.

Close the radio and put all the screws back into place.

And you're ready to rock! That is it, unless you want to add decorations. Check out the picture of me with the radio clipped onto my pants. I can go into a city corner trow my hat on the ground and play for money.