Car radios have been in existence since 1930. Back then, you could get an AM radio added to your car for $130, roughly $1,500 in today’s money. Thankfully, you don’t have to spend extra money to get a car radio today. Better yet, you can plug a phone, tablet, or MP3 player into your speakers, or connect via Bluetooth. This is way better than the tape decks and CD players we all grew up with. However, the sound isn’t always good quality. Depending on your vehicle, you might experience some hissing or static when listening.
A ground loop noise isolator is one solution to this problem. You plug your Bluetooth aux adapter into it, and plug the isolator into your car’s 3.5mm jack. Suddenly, all the signal noise is gone, as if by magic. Ground loop noise isolators aren’t just for cars, either. You can also use them with your home stereo system, to get a better signal on your Bluetooth speaker. And they’re not just for Bluetooth. You can also use them to connect your headphones, or anything that connects via 3.5mm aux. But as with most electronic equipment, not all ground loop noise isolators are not created equal.
Today, we’re going to review three of the best ground loop noise isolators on the market. We’ll look at all of their features, and see how they stack up to each other. The first option on our list is the BESIGN Ground Loop Noise Isolator. This is a robust, beefy noise isolator, with a short, 8.5-inch cable. The next one we’ll look at is the AUKEY Ground Loop Noise Isolator. This is a very compact device, and sports a 24-inch cord. Finally, we’ll check out the Mpow Ground Loop Noise Isolator. This is a mid-sized device, with a long, 3.3-foot cord. Which one is the best of the bunch? Let’s take a closer look, and find out.
What Causes Ground Loop Noise?
So, what causes static when you plug into an aux jack? For our purposes, we’ll be talking primarily about automotive stereo systems. But the same principles apply in a home stereo system.
The first thing you need to understand is that noise is caused by an interference in the electrical signal. Because stereo systems are full of electronic components, noise is actually inevitable. Manufacturers have known this for years, and install a noise cancelling circuit on the audio input circuit. These circuits work by measuring the signal from the RCA cable’s center conductor. The signal is then compared to the signal on the RCA’s shield, which is called a “reference” in electrical jargon. The difference between the signals is then amplified, which eliminates the noise.
At least, this is true in theory. However, there are a few things that can go wrong with this. First off, the audio cable’s ground needs to be completely isolated from the amplifier’s internal chassis ground. A cheaply-manufactured amplifier – or one with a defect – might not fully isolate the grounds. This creates what’s called a “ground loop”, where some voltage flows from the chassis ground to the RCA ground. This creates noise in the signal after it’s already gone through the noise cancelling circuit.
There are additional problems that pop up when you install an audio signal in a car. In most vehicles, the amplifier is located in the back of the car. Some manufacturers use the amplifier ground as a reference, instead of the head unit. The problem is that as the RCA cable runs from the rear of the car to the head unit, the noise changes. As a result, the noise cancelling circuitry has the wrong reference. As they say in computer programming, “garbage in, garbage out”. It’s not going to work properly.
Okay, that sounds pretty complicated. Let’s simplify it by using an everyday example: the humble bicycle. Picture a brake cable. It consists of two parts: an outer casing and a center cable. In this example, the cable is the main RCA signal, and the outer casing is the reference. When the inner cable moves relative to the casing, it moves on the other end, where the caliper is. It doesn’t matter how far apart the opposite ends of the casing are. When you turn the handlebars, your brake calipers remain open.
Now, imagine a brake cable that has no outer casing. It’s just a bare cable connected from the lever to the brake caliper. In this case, the brakes would only work when the handlebars were perfectly straight. If you turned the handlebars one way, the cable would slacken. When you squeezed the brake lever, the calipers wouldn’t tighten because of the slack. If you turned the other way, the cable would tighten, and the brakes would engage, causing you to crash. Without a reference, there would be noise in the signal.
Now, let’s imagine you wrap a huge rubber band around the brake lever and the rear caliper. You adjust the brakes so that they work correctly when the bike is going straight ahead. Then, when you turned the handlebars, the brakes still wouldn’t work correctly. They’d work to some extent, but the rubber band would still be exerting some control over the braking. This is analogous to a ground loop, and the noise it creates in your system.
How Does a Ground Loop Noise Isolator Work?
So, how does a ground loop isolator correct for the noise? A ground loop noise isolator has a separate isolation transformer on each channel. The transformer magnetically transfers the audio, but will not transfer electricity. As a result, the DC noise caused by the ground loop is eliminated. Of course, this assumes that there’s no interference introduced after the signal passes through the transformer.
Unfortunately, most ground loop noise isolators require installation inside of the electrical system. If you run a Google search, most of the results you see will be RCA devices. This means you have to tear your car apart and perform a complex physical installation. It works, but it can be a pain. The options we’ve chosen plug directly into your car’s 3.5mm aux port. On the one hand, they won’t remove noise from devices that don’t input through your aux port. For example, you might still get ground loop noise from your radio. But when you’re using an aux input, the signal will be crisp and clear. Moreover, installation is as easy as it gets. Just plug them in, and you’re ready to go.
BESIGN Ground Loop Noise Isolator
The BESIGN Ground Loop Noise Isolator consists of a fob attached to an 8-inch 3.5mm cable. It’s designed to be as light as possible, and tips the scales at only 0.81 ounces. The fob itself is also compact, measuring only 3.5 inches long, 1.5 inches wide, and 1 inch thick. This compact size and light weight make it ideal for automotive use. Plug it into your aux jack, and you won’t have a long cable flapping around in your vehicle.
The design of the fob is attractive. It has soft, rounded corners that won’t hurt if you bang into it. The shell is a glossy black ABS plastic that’s attractive to look at. On the top, there’s a white BESIGN logo on an oval plate that looks like black stained wood. The design is also nice and sturdy. Where the cable connects, there’s a flexible rubber reinforcement that prevents damage from twisting.
Like all the ground loop noise isolators on our list, the BESIGN isolator is bi-directional. This means that it can pass a signal in both directions. As a result, you’re not just limited to listening to music. You can also use a Bluetooth fob to connect your phone for hands-free calling. The noise isolating system is very effective. You won’t hear any static, pops, or other unwanted artifacts.
AUKEY Ground Loop Noise Isolator
The AUKEY Ground Loop Noise Isolator has a similar design to the BESIGN isolator. It consists of a fob on the end of a 24-inch 3.5mm aux cable. This cable is a double-edged sword. On the one hand, it’s probably more cord than you want to deal with in your car. On the other hand, it makes the AUKEY isolator more versatile. For example, you can use it in your home stereo system. With a shorter cable, placement on a home stereo system might be difficult or inconvenient.
The fob itself measures 2.3 inches long, 0.8 inches wide, and 0.8 inches thick. And at 1.58 ounces, it’s fairly lightweight. But why does it weigh almost twice as much as the BESIGN fob? The difference is that it has more robust internal electronics. The transistors are of a higher quality, and do a better job at noise isolation. That said, for some reason, it seems to cut out some of the bass. It’s not terrible, but it’s noticeable if you’re an audiophile. Then again, you can just adjust your stereo’s EQ to compensate.
The fob is sturdy and attractive, with a satin black ABS plastic shell. The edges are all rounded, which makes it safer as well as more attractive. There’s a glossy AUKEY logo on the top, and a reinforced cable to prevent damage. Best of all, if it does get damaged, you’re protected by AUKEY’s 24-month manufacturer’s warranty. If anything goes wrong, just file a claim for a free replacement.
Mpow Ground Loop Noise Isolator
In most respects, the Mpow Ground Loop Noise Isolator is virtually identical to the BESIGN isolator. It’s a bit more compact, measuring 2.01 inches long, 0.59 inches wide, and 0.59 inches thick. It’s also lightweight, weighing in at just under an ounce. The fob is a glossy black ABS plastic, with a rectangular form factor. On the front face, there’s a white Mpow logo, and the cable is reinforced where it joins the fob. In addition to an impressive 24-month warranty, you also get a 45-day money back guarantee. During that period, if you don’t like it, just send it back.
The noise isolation is very good, reducing almost all the noise in the signal. Popping, crackling, and static are all virtually completely removed. However, the cable is 3.3 feet long. This might be a bit longer than is ideal for automotive use. On the other hand, it’s great for home use. You can plug it into your stereo system. Even if you plug into the back of the stereo, you can still wrap it around to the front with no issues.
As you can see, there’s not really very much difference between these devices in terms of quality. They all come from well-regarded manufacturers, and you’re not going to be disappointed with any of them. This is to be expected. A ground loop noise isolator is a pretty simple device. It might be tough to explain how they work, but they utilize well-understood principles of electronics. Unless there’s a manufacturing defect, it’s going to get the job done. There’s one exception to this, which is the AUKEY Ground Loop Noise Isolator. This option offers slightly better noise isolation at the expense of some loss in bass output. As a result, it’s better for phone calls and not as good for music. But the difference is minute.
The BESIGN Ground Loop Noise Isolator and the Mpow Ground Loop Noise Isolator are basically identical. At least, this is true in terms of audio quality. However, there are still a couple of differences in terms of physical design. The BESIGN Ground Loop Noise Isolator has a fairly short cable. At first, this might not seem like a good thing. But it’s very useful for automotive use. You won’t have to worry about what to do with a long cable. By contrast, the Mpow Ground Loop Noise Isolator has a longer cable. This makes it better suited for home stereo systems, especially if the aux jack is located on the back.