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Editor's note, July 16, 2017: We updated this story with new illustrations and new tips and tricks.

So you just need to open the box of your new entertainment device, connect everything together, and you will hear hum, whine, hiss, chatter, or any other annoying noise that is known to plague audio devices. You may even see some stripes or waves on the TV. So you take it all back to the store and only see the salesperson plug it in and make everything work. what……?

I would love to tell you that you did nothing wrong, but you may have, at least inadvertently. Again, it could be poor wiring, defective equipment, or just a noisy electronic environment. No matter what type of noise you hear—regardless of the cause—here is the way to get rid of it.

Note: Some noises are inherent, such as tape hiss, or hiss when you increase the input gain. It is part of the equipment, and usually the only treatment is...better equipment.

The number one cause of abnormal audio noise and strange video is ground loops because it is very easy to create. The most common manifestations are loud buzzing or buzzing from speakers, or scroll bars on the TV screen. It may also be a quieter but equally annoying buzzing or buzzing sound that can only be heard when the room is quiet.

When one or more parts of your entertainment system are plugged into AC (alternating current) at different locations and then connected together through electrical (and optical) signal cables (RCA, HDMI, composite, components), a ground loop usually occurs. The shielding layer is grounded. In the simplest terms, this creates a single loop antenna that likes to absorb various types of noise through electromagnetic induction. You can see how to create a loop in the image below.

Anything that breaks the loop will eliminate the noise, and the easiest way is to power all devices through an AC power outlet. As shown below, just plug all your devices into a single power strip, surge protector or power center, and then plug them into the wall. The problem is solved. Most multimedia settings can be easily handled by a single 10 amp circuit, and most household circuits can at least handle it.

In some cases, you may not be able to use one device to reach the same outlet. Self-powered speakers and subwoofers come to mind. You can "pull the ground" by using a three-prong to two-prong adapter, but this represents a potential electric shock hazard. Find an extreme example of Lee Harvey and Stone the Crows that illustrates what happens when using high-power devices.

If it is impractical to use an extension cord, you can purchase a hum eliminator, such as Ebtech's Hum X. But it costs $70. There are other products with roughly the same function, some of which interrupt the loop in the signal cable, but they are also very expensive. If you have the relevant skills, you can build your own silencer for about $10 or $15. You will find a lot of information on the Internet to show you how to do it, but this task requires moderate skills with a soldering iron and similar tools.

Ebtech's Hum X can safely eliminate ground loop noise. If you have the skills, there are also online DIY solutions that are cheaper.

If these methods do not solve the problem, the problem may lie in the over-the-air (OTA) antenna or the cable television coaxial cable with its own ground path. When dealing with the coaxial signal splitter, I received some very annoying vibrations. Usually—due to the isolation built into cable modems, cable boxes, and similar devices—this happens only when you connect directly to a TV or VCR.

If you have traced the problem to the TV signal cable connected to a cable modem or similar device (disconnect it and see if the problem disappears), replace the device-it has a problem. If you connect directly to the TV, you can use a ground loop isolator for $20 to $30.

Ground loop isolator for coaxial (antenna and cable television) cables.

Ground loops are not the only cause of electrical noise. Almost any device with a motor (such as hair dryers and blenders) as well as dimmers and failed fluorescent lights can cause this interference. It may be heard through your audio equipment or visible on your TV, or it may not. The obvious solution to this noise is not to use these types of devices while you are watching TV or listening to music. If you live alone, you may be able to do this. If there are other people under the same roof, maybe not. 

If you are willing to be separated from several Benjamins, you can ensure that you get the original AC power without ground loop noise by using an online UPS (uninterruptible power supply) or an isolation transformer. On-line UPS is a battery backup system whose battery is always used between input AC power and output AC power (online). This requires the power supply to be converted to DC (direct current) and then to AC, which will eliminate all noise. This is also called double conversion.

Tripplite's SU1000XLCD is priced at US$630, but it does a better job of regulating power than so-called audiophile units that are 10 times more expensive. If you are not worried about ground loops, you can spend more than $100 to find a UPS that can eliminate AC noise (look for a sinusoidal output).

Real online UPS is expensive. The SU1000XLCD UPS sent to me by Tripplite is used to clean up the super dirty air conditioner in my apartment. For example, the cost is about US$630. It is also heavy, about the size of a small dehumidifier, and has some functions that are not related to noise elimination (such as USB monitoring so that the connected computer can be shut down normally in the event of a power failure). However, if it is not 100% effective and comfortable protection against power surges and power failures, it is damned.

It is also much cheaper than the high-end power conditioners you see sold to scam-prone audiophiles. If you are not worried about eliminating ground loop noise, you can buy a UPS that advertises sine wave output for no more than $100.

It is a bit cheaper than online UPS, but it is the isolation transformer that is absolutely effective against various line noises. Tripplite also sent me one of them: an excellent 1000 watt IS1000HG (hospital grade) with four sockets. It is about US$500, but you can easily buy a lower wattage (500 or 250) model for less than US$250. Please note that I have seen much cheaper on Amazon, but not from well-known suppliers, so I cannot guarantee them.

The isolation transformer is one of the products whose name describes the tee-it uses a special shielding transformer to turn dirty AC power into clean AC power through electromagnetic induction-yes, this is the same thing that causes ground loop noise.

Isolation transformers are designed for use in sophisticated diagnostic equipment, in which even extremely noisy alternating current can cause false readings. This means that they are sufficient for multimedia settings.

The back of the IS1000HG isolation transformer is designed to eliminate all AC noise that may affect sensitive test equipment. It is also suitable for entertainment systems.

For cables and noise, there are actually only one or two hard and fast rules. The first is to never pass the power cord through or close to audio or video signal lines, including antenna lines. Modern signal cables are well shielded, but if you hear a buzzing sound and it is not a ground loop, this is most likely the cause. Please note that the cable connected to the self-powered speaker (non-Wi-Fi) is an audio signal cable, not an output cable.

Also note that compared to a two-wire cable, a three-wire balanced signal cable (transmitting two signals, one with opposite polarity—just like the famous humbucker pickup) has a much smaller effect on power line hum and other noise . If your device allows you to choose to use balanced output or input, XLR or TRS (Tip/Ring/Sleeve), please do so.

Speaker cables, because the signals transmitted through them are much stronger, they should not be affected by hearing. But for safety's sake, please isolate the AC power cord as much as possible.

The red circle is the balanced input of this Yamaha HS7 speaker. Many high-end DACs and audio interfaces have corresponding outputs. The balanced connection eliminates any noise caused in the cable transmission signal.

Another rule of wires is not loop antenna signal cables (two-leads), which tend to cause the same noise by making them into antennas themselves. Electromagnetic induction; this is a blessing and a curse. (If you don’t know)

Regarding the quality of the cables: Inferior cables can cause noise problems, but there is no real benefit to spending a lot of money on cables. A common misconception is that the more expensive the metal, the better the cable. Incorrect. Gold is used in connectors because it does not oxidize, not because it is the best electrical conductor. Quite good, better than nickel and chromium, but actually a bit worse than silver and copper. Forget platinum-it sounds sexy, but it ranks about 20th on the conductivity list.

Copper wire and gold connector are the best combination; but again, don't listen to the sales promotion of high-quality audio. There are many cables that cost $10 to $20 (or even lower) as well.

One thing you can check is that although this is mainly an issue in high impedance (higher gain/voltage, aka Hi-Z) applications, such as guitar cables, they are not microphones. Poor or loose shielding and other factors can actually convert physical shocks into audio signals. I'm not kidding. I have encountered this situation in my life using only component connection cables, which are used for turntables. However, if you notice strange noises that seem to be synchronized with bass or vibration, tap the signal cable with your finger (with the device turned on) to see if there is a problem.

There is also a wire problem: size. Although when driving speakers by reducing the cable impedance (resistivity), larger wires can actually help the amplifier work more easily and cooler, but the impact on the signal cable is negligible. In other words, for those who have not paid a lot for the thick line and need to hear the difference, this is inaudible.

Ever wondered why the walls of your stereo receiver and other electronic devices are metal, while everything else in the world seems to be made of plastic? It is not for tensile strength, but to prevent incoming and outgoing RFI (Radio Frequency Interference). Any conductive material will block the radio frequency signal and shunt its charge to its surface. In fact, the shield on the cable is like a Faraday cage.

But the actual implementation of Faraday cages (for example, not lining your TV room with a copper sheath) can only do so much, so you may need to reduce the signal strength they must handle. I'm talking about portable phones, cell phones, Wi-Fi devices, and even computers.

If the Faraday cage can prevent this, then the radio frequency around the multimedia device should be no problem.

Computers can generate a lot of radio frequency, which is why I avoid the fancy transparent plastic side, which allows it to get in and out. I have also heard that wireless peripherals, such as mice, can cause interference. This is a malfunction or improper design, and the only solution is to replace them.

Back to the topic: Don’t be too paranoid about this, but it’s not a bad idea to keep your RF transmitter as far away as possible from your multimedia settings. If it is a device close to your settings, make sure it is sufficiently shielded.

I use external USB and Thunderbolt audio interfaces because they sound much better than anything you find on the motherboard. Believe me, if my old ears can hear the difference-it is the difference. But when I first started using it, I occasionally heard very weak static electricity. Due to quite complicated reasons, current may leak into the shielding layer of the USB cable, thereby affecting the signal. This is annoying.

There are three ways to eliminate USB (and HDMI) cable noise. One is to use a cable with a ferrite noise suppressor sleeve (a large round piece at one end. You can also buy a clip-on ferrite noise suppressor). These are sometimes called ferrite beads.

HDMI cable with ferrite noise filter to prevent stray current passing through the shielding layer.

The second method is to use a wire with a lower resistance than the USB/HDMI cable to shield the shell of the USB audio interface or the audio component of the HDMI connection to the shell of your computer. The speaker wire is working properly. Electricity always flows along the path of least resistance, so stray current flows along the ground wire instead of the cable shield. This is also called a ground shunt, or simply shunt.

The third method is to get a USB noise filter (I have never seen a filter for HDMI, but an HDMI adapter can work), which is actually a USB repeater with a split shield connection. These costs are about $50, and it is said that they can indeed eliminate noise. I have never used it, because the first and second methods are much cheaper and have never let me down.

Another reason I use external USB and Thunderbolt interfaces is that they are not affected by too much RFI. Internal audio solutions, especially those located on the motherboard, are susceptible to various line noises and electromagnetic interference that cannot be eliminated. You may have noticed that I just provided you with a solution-use external USB or Thunderbolt. In other words, PCI and PCIe cards can also solve this problem and provide more output for games and surround.

Using the above method, you should be able to eliminate all noises that are not inherent in the audio system, and some noises that you might think are inherent. However, if you encounter a noise that I have not covered, or have an effective homemade solution, please share with us by commenting on our Facebook page and/or sending an email to jjacobi@pcworld. com.

Jon is a musician trained by the Juilliard School of Music, a former x86/6800 programmer, and a long-term (late 70s) computer enthusiast, living in the San Francisco Bay Area. jjacobi@pcworld.com

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