Lesson: Learn How to Build an Amp from an Old Radio
Looking for a new project and a sick way to add some spice to your music gear? Learn how to build an amp from an old radio!
This interview originally appeared in She Shreds Magazine Issue #19, released December 2019.
Learning how to build an amp from an old radio is not only a sweet upcycling project, but it’s also so easy that it blew my mind. The coolest thing is how unique each radio can look and sound: an older radio might offer a vintage or low-fidelity tone, while a newer radio might offer more portability or a cleaner sound. Your new amp will be one of a kind!
Here’s everything you’ll need to complete this project:
- Soldering iron*
- Soldering wire*
- 22 AWG silicone wire
- 1⁄4” mono female jack
- Phillips head screwdriver
- Flathead screwdriver (or something flat)
- Wire cutter (or scissors)
- Guitar & instrument cable
- Drill (optional)
*If you’ve never soldered anything before, here’s a link to a cool video to help you get started.
Step One: Choosing Your Radio
Finding your perfect radio could be as easy as taking a trip to the local thrift store or doing a quick search on eBay. When on the lookout, try keeping in mind which features are most important to you. Some radios have tone, equalizer, or squelch knobs that would allow you to have more control of your final sound. Some are battery-powered, have a built-in handle, or a headphone jack—all of which would make them a sweet travel companion.
Step Two: Rip That Machine Open
Once you’ve found your dream radio, it’s time to rip it open (as gently as possible).
To start, you’ll need to remove any knobs or switches from the radio. This can be done by placing a flathead screwdriver in the space between the knob and body of the radio and lifting it up.
Next, you’ll need to remove any screws holding the outer casing together. These will usually be found in the corners on the back of the radio, and sometimes there may be one or two hidden in the battery tray.
Once you’ve removed all of the screws, opening up your radio could be as simple as pulling one side apart from the other, but you might need to stick your flathead screwdriver in the lip between each side for leverage. (Similar to the knobs.)
Now that your future amp is ripped open, it’s time to locate the circuit board. Mine was protected under my radio’s control plate. They’re pretty easy to recognize, but yours might be flipped over or protected like mine, so you’ll need to remove any screws holding it or its cover in place to gain access.
Step Three: Prepare Your Jack
Now you’ll need to get your quarter-inch jack ready for the job of its lifetime… Start by cutting yourself a couple pieces of wire. Make sure to give yourself enough slack for when it’s time to decide where your jack will rest. Next, you’ll need to strip both ends of each wire to expose them. I used scissors to do this, but a wire cutter or wire stripper would be the better option.
Now that your wires are prepared, you’ll need to solder them onto your jack. When looking at your jack, you’ll notice two small pieces sticking out across from each other. These are called solder lugs. One will be connected to the center of the jack and slightly shorter; this part of the jack is called the sleeve and will be for your ground wire. The other will be more towards the outside and slightly longer; this part of the jack is called the tip and will be for your hot wire. To understand the difference between the tip and the sleeve, take a look at your instrument cable. It also has a tip and sleeve that are usually separated by a thin black line. On the cable, the tip is hot and provides the sound coming from your guitar and the sleeve acts as a ground signal that helps contain any unwanted noise coming from the guitar. The jack conducts these signals when your cable is plugged in.
If you have multi-colored wire, this makes the organization of this step much simpler. I used my black wire as my ground wire and soldered it to the center lug of my jack. Then I used my red wire as my hot wire and soldered it to the outer lug of my jack.
Step Four: Locating the Volume Pot
With your jack prepared, it’s time to figure out where to connect it on the circuit board. You’re looking for the piece called the volume pot. It’s pretty easy to find because it’s what your volume knob attaches to. It’s also easily recognizable because it will have multiple solder lugs. Here’s what mine looks like:
To find out which lug you’ll be attaching your wire to, you’ll need to do a little experimenting. Start by plugging your instrument into your jack.
Next, you’ll need to find a negative point on your radio to solder your ground wire to. The easiest spot to find is the negative terminal used for the radio’s battery case. Something should already be soldered there, so you’ll just need to solder your wire to the same spot.
Now you’ll need to power on your radio. With your hot wire in hand, locate the volume knob and start placing the tip of your wire on each lug while strumming your guitar or playing your instrument. You’re looking for the lug that not only amplifies your instrument, but also allows the volume knob on the radio to control your instrument’s volume. Once you’ve found it, turn your radio off and solder your hot wire onto it.
Step Five: Putting It Back Together Again
Now that you’ve got the amp working, it’s time to put it back together again.
First, you’ll need to find a home for your jack. Unplug your instrument cable and experiment with different spots on the amp. You’ll need to make sure your jack has enough room to not interfere with the other parts coming from the circuit board, and that you’ll be able to close your radio completely.
Once you’ve found your spot, cut a hole into the casing of the radio that’s big enough to place the tip of your jack into. After removing the washer and nut from your jack, cut your hole using a drill or sharp object. When your jack fits through, reattach the washer and nut to secure your jack in place.
Next, you’ll need to reattach your circuit board and/or cover if you removed them. Following that, close your radio up and reattach the screws and knobs that were removed at the beginning.
If you’ve made it this far, then you should be the proud new owner of a sick guitar amp that you put together yourself! Pretty sweet, right?