Ground loop isolators are used to break the DC circuit path for the audio shield ground circuit.
Note: This next paragraph will become agonizingly redundant. It is an attempt to make the concept clear to those who are new to car audio.
Ground Loops: Every piece of car audio equipment has some type of noise canceling circuit on the audio input circuit. These input circuits will, ideally, completely isolate the audio’s shield ground from the amplifier’s internal connection chassis ground. The amplifier’s input shield connection (if properly designed) will have virtually no connection to the amplifier’s power ground. It should take the signal from the RCA cable’s center conductor, compare the center conductor’s signal to the RCA’s shield (the reference) and amplify the difference between the two. Remember the voltage generated in the body (voltage drop across the chassis from other electrical accessories)? Well if the amplifier used the ground in the rear of the vehicle (where the amplifier is mounted) as the audio reference instead of the shield ground (which is referenced to ground at the head unit’s mounting position) as a reference, the voltage generated through the body would become part of the amplified signal. The amplifier would amplify the difference between the signal on the center conductor of the RCA cable and the amplifier’s ground (in the rear of the vehicle). Some manufacturers use poorly designed input circuitry which allows the equipment’s power ground to have too much of an influence on the signal (not enough isolation). This causes a small amount of fluctuating DC current to flow through the audio shield which allows noise (from the voltage drop across the chassis) to enter the signal path. The 2 ground paths create a ground loop.
Lame Analogy: For those of you who are more mechanically inclined, try to think of it as a brake cable for the rear brakes on a bicycle. You know that there’s an outer casing and a center cable. If there was no outer casing (only a cable connected to the brake lever). The brakes would work properly only when the handle bars were in precisely the right position (straight ahead for this example). If the handle bars were turned a little to one side (let’s say left), the cable would get slack and could not possibly tighten the calipers onto the rear wheel. If the handle bars were turned sufficiently to the right, the cable would tighten and the brakes would be applied no matter whether the brake lever was pulled or not. The brake cable’s outer casing acts as a reference for the braking system. If the inner cable at the brake lever end moves 1 inch with reference to the casing, it will do the same thing on the other end (the caliper end of the cable). It does not matter how much the two opposite ends of the cable (as a whole) are moved (with reference to each other). The RCA cable provides a reference along with the signal to make sure that the signal is accurate when it reaches the other end. If you want add a ‘ground loop’ to the braking system, imagine a stiff rubber band connecting the brake lever to the rear caliper. If you adjusted the brakes to operate properly with the handle bars straight, the braking would not work precisely the same when you turned the bars to either side. The brake cable would dominate the braking operation and the brakes would probably work fairly well, but not perfectly because there would be 2 different forces trying to control the rear caliper. This would form the mechanical version of the ground loop.
Construction: A ground loop isolator uses an isolation transformer for each channel. The transformers generally have a 1:1 ratio which neither boosts nor cuts the audio level. They are typically bi-directional (either end can be and input or an output) but there are some that have and input and an output. When you see the jacks/plugs marked as input/output, connect it as indicated. In the isolation transformer, the audio is magnetically coupled through the transformer’s core. Since DC cannot flow the transformer, the DC path is cut and the noise is eliminated (if the noise was caused by a ground loop).
The following is an example of a generic ground loop isolator.
Юрий Семендяев
АВТОРСКИЙ БЛОГ
Как изготовить простейший «изолятор земли»:
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Здравствуйте, я Юрий Семендяев. Мои интересы: электроника, фотография, комнатные растения. Буду рад всем читателям моего журнала.
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Июль, 15, 2012
Как изготовить простейший «изолятор земли» @ 20:15
После подключения антенного входа компьютерного ТВ-тюнера к свободному выводу сплиттера, распределяющего сигнал кабельного провайдера между тремя телевизорами, обнаружился неприятный момент. Изображение на мониторе стало мерцать с неприятной для глаз частотой. Что характерно, мерцало изображение не только отображаемого телеканала, но и любое другое, формируемое видеокартой компьютера.
«Изолятор земли» промышленного изготовления
К сожалению, в городе готовое устройство отыскать не удалось, а платить китайцам на e-bay примерно 40-50$ было неприемлемо, попытался сделать «Изолятор земли» самостоятельно по такой схеме.
Были приобретены два «F-разъема, гнездо на корпус с фаской» по цене 10 рублей за штуку,
«F-разъем, гнездо на корпус с фаской»
конденсаторы выпаяны из старого советского телика,
а в качестве корпуса использована пластиковая баночка для цветной фотоплёнки ORWO (была такая в СССР, если кто помнит).
Встречались плёнки в алюминиевых баночках с пластмассовой крышкой. Они больше подходят для изготовления, потому что алюминиевый корпус играет роль экрана, правда, внутри нужно будет предусмотреть какую-либо изоляцию, чтобы после сборки элементы схемы не замкнули на корпус.
Вот, что получилось после соединения всех деталей. Лепестки вырезал из консервной банки.
«Изолятор земли» внутри
Готовый«Изолятор земли»
Готовый«Изолятор земли» с прикручеными гайками для телевизионного кабеля
ground loop isolator
1 ground loop
bypass loop — байпасный контур; байпасная петля
2 unit ground loop
Тематики
3 unit ground-loop
Тематики
4 ground loop
контур заземления заземляющий контур — [Я.Н.Лугинский, М.С.Фези-Жилинская, Ю.С.Кабиров. Англо-русский словарь по электротехнике и электроэнергетике, Москва, 1999 г.]
контур заземления заземлитель Система расположенных в земле неизолированных горизонтальных и вертикальных проводников (электродов), объединенных между собой и обеспечивающих контакт с землей заземляемых конструкций. [Инструкция по заземлению устройств электроснабжения на электрифицированных железных дорогах]
Тематики
Синонимы
5 ground-loop currents
Тематики
6 ground loop impedance
полное сопротивление контура замыкания через землю — [Я.Н.Лугинский, М.С.Фези-Жилинская, Ю.С.Кабиров. Англо-русский словарь по электротехнике и электроэнергетике, Москва, 1999 г.]
Тематики
7 ground loop
8 unit ground loop
9 unit ground loop
10 ground loop
11 ground-loop
12 unit ground loop
13 unit ground-loop
14 ground-loop currents
15 ground loop
16 ground loop impedance
17 ground loop transformer
18 ground-loop
19 ground-loop currents
20 ground-loop impedance test
См. также в других словарях:
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Guide to the Best Ground Loop Noise Isolator
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.
Final Verdict
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.
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