DIY 9v Snap to Barrel Jack Adapter

A simple, easy to make adapter to power pedals from a battery.

It’s often nice to have the ability to power a pedal with a battery instead of plugging it in to a power supply. Some pedals even work better when powered with a battery. The problem is that many pedals aren’t equipped with 9V battery snaps. So years ago (when I was a teenager), I started making these little battery snaps because back then these things weren’t as easy to come by as they are now. Now you can buy them online, but why spend money and wait for shipping when you have all the parts to make one yourself. All you need is a 9V battery (dead or alive) and an old wall wart with the proper sized barrel jack.

  1. The first step is to extract the terminal clip from the 9 volt battery. I do this by peeling back the metal casing with some snips. The terminals are attached by some very thin sheet metal to the battery array inside the casing…this can easily be clipped off.

2. The next step is to cut the barrel jack from wall wart power adapter. You can decide how long you want the length of the wire to be. But you need at least an inch or two so there is enough wire to solder it to the terminals. I usually make it around 3 inches long.

3. Now we need to find out the polarity of the barrel jack. A continuity test will tell us which wire is connected to the center of the barrel jack, and which wire is connected to the sleeve. Often times the wires on wall warts can be differentiated by a series of ridges along the length of one wire. Sometimes one wire has a stripe on it. Either way, make note of which wire is attached to the center pin and which wire is attached to the outside sleeve of the barrel jack.

4. Next we need to make note of which battery snap terminal will be attached to the is positive side of the actual battery, and vice versa. I usually remind myself of the polarity of a battery by looking at a different 9V battery. The positive (+) side is always labeled. Snap the extracted terminal clip onto the battery and note which side is connected to the positive terminal…it’s the bigger one.

5. Now we just need to solder the wire attached to the sleeve of the barrel jack to the positive battery terminal; and solder the wire attached to the center of the barrel jack to the negative battery terminal…as is the standard with modern pedal power jacks.

6. Double check that the polarity is correct by using a continuity test. The center of the barrel jack should be connected to the negative terminal and the sleeve of the barrel jack should be connected to the positive terminal.

7. The next step is to cover the solder joints with hot melt glue. I like to use black glue because I think it looks nice, but looks don’t matter as much as the fact that the solder joints are electrically isolated from possible shorts. Once the back of the battery clip is covered with hot glue, you might need to trim of any excess that runs over the edge.

8. The last step is to test it on a real pedal…it works!

That’s it! Enjoy powering your pedals with a battery!

About Brach

Brach has always had a deep fascination with how and why things work. He has been tinkering with technology since he was 4 years old when, with overwhelming curiosity, learned how to pry apart his mechanical and electrical toys with a flat head screwdriver. He has been repairing technical devices since he learned how to put those toys back together again a few years later.