As an Amazon associate we earn from qualifying purchases. Thanks for your support!                               
×

Best Blu-ray Movie Deals


Best Blu-ray Movie Deals, See All the Deals »
Top deals | New deals  
 All countries United States United Kingdom Canada Germany France Spain Italy Australia Netherlands Japan Mexico
Back to the Future Part II 4K (Blu-ray)
$24.96
3 hrs ago
Back to the Future: The Ultimate Trilogy 4K (Blu-ray)
$44.99
 
The Toxic Avenger 4K (Blu-ray)
$31.13
 
Vikings: The Complete Series (Blu-ray)
$54.49
 
House Party 4K (Blu-ray)
$34.99
1 day ago
The Lord of the Rings: Return of the King 4K (Blu-ray)
$29.96
 
The Breakfast Club 4K (Blu-ray)
$34.99
 
Lawrence of Arabia 4K (Blu-ray)
$30.52
 
Teenage Mutant Ninja Turtles Trilogy 4K (Blu-ray)
$70.00
 
Starship Troopers 4K (Blu-ray)
$26.95
 
Jurassic World Rebirth 4K (Blu-ray)
$29.95
 
Pale Rider 4K (Blu-ray)
$28.24
5 hrs ago
What's your next favorite movie?
Join our movie community to find out


Image from: Life of Pi (2012)

Go Back   Blu-ray Forum > Home Theater > Home Theater General Discussion


Reply
 
Thread Tools Display Modes
Old 05-07-2009, 12:08 AM   #1
Big Daddy Big Daddy is offline
Blu-ray Champion
 
Big Daddy's Avatar
 
Jan 2008
Southern California
79
122
1
Default Ground Hum & Ground Loop Isolators

GROUND HUM
  1. Generally, a ground loop is formed when an electrical system has more than one path to the electrical ground. The path between these points form a loop that works like an antenna and picks up noise. Grounding problems are normally found because you are using 2 prong and 3 prong power cords and plugging them into different wall sources.
  2. You need to find the source of the problem. The only way is to unplug them one by one to see what is causing the hum.
  3. Usually, the most common sources are cable TV boxes and computers that are connected to an A/V receiver. Unplug the cable box and/or the computer and see if it improves the hum.
  4. Sometimes, changing the wall outlets solves the problem.
  5. Don’t run interconnect and speaker cables parallel to power and extension cords.
  6. Don’t coil up the excess length of a cable. If you have excess cables, instead of coiling them, you should make a figure 8 with them.
  7. Use an RG6 digital coaxial subwoofer cable and move it away from the other cables. This may help.
  8. Buy a good power conditioner/surge protector and plug all your equipment into that one, including the subwoofer amp. Make sure the coax cables for the cable TV also go through the conditioner. This may solve your noise problem.
  9. Buy a ground loop isolator.
http://www.partsexpress.com/resources/subwoofer.html
Quote:
  • When I hooked up the RCA cable to my receiver from my subamp, it began to make an audible hum. Is it defective? Likely it is NOT defective. What you are hearing is called a "ground loop" and is caused by uneven ground potentials at various locations in your audio system. These potentials cause small levels of electricity to flow through the ground paths, which will often be amplified as a 60 Hz hum.
  • How do I stop it from humming? One of the first things to try is changing the outlet into which the subwoofer power is plugged. Since often a subwoofer is located away from the rest of the equipment, many times the outlet will be on a different circuit or have a different grounding point. Try connecting the subwoofer to the same outlet as the rest of your equipment via an extension cord or power strip. The next thing to check is the cable TV feed going into your system. While this at first seems like a silly idea, if you consider the web of connections in your A/V system, it begins to make sense. Temporarily unhook the main cable connection and see if the hum stops or is reduced. If it does, the easiest solution is to purchase a coax isolation transformer such as our #180-075. If this does not completely solve the problem, try unhooking the connections of different components in the system and see if the problem stops. If it does, consider using a line-level ground loop isolator in that location. Our #265-012 works well. If nothing seems to quite eliminate all hum, the #265-012 can be used directly on the subwoofer line-level feed and generally will solve most problems.
  • What if the subwoofer hums when it is not plugged into anything but the wall outlet? If there are mechanical hums or consistent loud hums coming from the speaker when nothing is connected, then it is likely defective. Contact customer service for assistance.
  • What if I hear a buzzing noise? This is usually from external sources such a fluorescent lights and light dimmers. Fluorescent lights radiate electro-magnetic interference (EMI) that can get into a bad or cheap RCA patch cable. Low voltage light dimmers often put noise directly onto the house electrical wiring. Test by turning these types of lighting off, making sure that the dimmer has a complete "off" position. Many of the "slider" or "rotary" dimmers do not have a completely off position even when at their lowest setting. If this is determined to be the source of the problem, try changing the circuit into which the subwoofer is plugged. As a last resort a line level ground loop isolator has been seen to improve this problem on occasion.
  • What if I hear a radio station? This is almost always a bad patch cable with leaks in the shield. Replace with a new or known good cable.
http://www.audioholics.com/education...-interconnects
Quote:
First, we want to minimize the common-mode voltage difference between the interconnected devices. If possible, plug everything into the same AC power outlet, or power strip. If that is not possible plug the interconnected equipment into power outlets that are on the same branch circuit (same circuit breaker). Another possibility would be to run an additional heavy gauge (low resistance) ground wire between the chassis of the two devices to divert some of the common-mode cable shield current.

Second, we want to minimize the resistance of the interconnecting cable shields. Use cables with a copper braid (or even spiral copper) shield instead of a foil shield. Use cables with the heaviest shield possible, or with double shields in order to minimize cable shield resistance. Do not use cables with aluminum foil shields, since their resistances are much higher. (Note: A foil-braid combination shield is fine, as long as the low resistance copper braid is present). Also keep cables as short as possible, since this will also reduce the total shield resistance.
http://www.epanorama.net/documents/g...oop/index.html
Quote:
Ground loop problems and how to get rid of them
Written and copyright by Tomi Engdahl 1997-2006

NOTE: The information presented here is believed to be correct and is made available here by the author. The author of this document is not liable for any effect this information or any use thereof may have.

The documents have been used and recommended by many people and are belived to be accurate. So accurate that they have also been featured as GB AUDIO Ground loops DATA SHEET on their web pages (with permission from me).

Basics
The dilemma is that solving "noise" problems is an art within itself. Since it doesn't come up every day, we all have limited practical experience. This has spawned an industry for those who are now specialize in solving noise problems.

A good power distribution system is essential for proper operation of audio system. Professional audio systems just doesn't work well with normal extension cords running hundreds of feet to a stage. Besides the power feed the good grounding of the whole system is essential.

Ground loop is a condition where an unintended connection to ground is made through an interfering electrical conductor. Generally ground loop connection exists when an electrical system is connected through more than one way to the electrical ground.

When two or more devices are connected to a common ground through different paths, a ground loop occurs. Currents flow through these multiple paths and develop voltages which can cause damage, noise or 50Hz/60Hz hum in audio or video equipment. To prevent ground loops, all signal grounds need to go to one common point and when two grounding points cannot be avoided, one side must isolate the signal and grounds from the other.

The bottom line is that a perfect "quiet" ground does not exist. The basics of all noise problems on the grounding system boils down to what is objectionable current. With the exception of hospital systems, the definition is vague at best. The standard electrical grounding system throughout the building isn't designed to have current constantly flowing through it--and yet it does, you cannot stop it. The reason a ground will not and never be perfectly noise free is that the grounding electrode conductor is nothing more than a long wire from point A to point B. And the longer the wire the more noise it will pick up.

Sound and video people are referring to the type of noisy ground with term like ground loops: current running the equipment grounding conductor, metal within the building, and grounding electrode conductor. Use of any of today's standard 120-volt or 230-volt single-phase AC systems mean potential problems for audio equipment. Computer guys have the same problem in their line of work and so forth.

Usually ground loops are an after-the-fact type of problem in which the end-user blames the installer, the installer blames the manufacturer, and actually nobody is at fault. Neither the manufacturer nor the installer can usually predict where a loop will occur. Only after the system is installed can it be determined if a problem will exist.

Ground loop problems can be corrected and avoided. It is important for the dealer, isntallee and the end user to be aware that this problem can occur. It is a good idea to design the system to avoid most obvious source of this kind of problems, and then be prepared still to face some problems when starting to use the system. A ground loop problem may occur at several points in the system, and each occurrence of the problem must be corrected individually.

Why grounding is so important?
Earthing of electrical systems is required for a number of reasons, principally to ensure the safety of people near the system and to prevent damage to the system itself in the event of a fault. The function of the protective conductor, or earth, is to provide a low resistance path for fault current so that the circuit protective devices operate rapidly to disconnect the supply.

The NEC, National Electrical Code defines a ground as: "a conducting connection, whether intentional or accidental between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of the earth." When talking about grounding it is actually two different subjects, earth grounding and equipment grounding. Earth grounding is an intentional connection from a circuit conductor usually the neutral to a ground electrode placed in the earth. Equipment grounding is to ensure that operating equipment within a structure is properly grounded. These two grounding systems are required to be kept separate except for a connection between the two systems to prevent differences in potential from a possible flashover from a lightning strike. The purpose of a ground besides the protection of people plants and equipment is to provide a safe path for the dissipation of Fault Currents, Lightning Strikes, Static Discharges, EMI and RFI signals and Interference.

Improper grounding can create a lethal hazard. Correct grounding is essential for correct operation and safety of electrical equipments. Grounding can solve many problems, but it can also cause new ones. One of the most common problem is called "ground loop".

What causes the humming in audio systems?
Audio and video systems need a reference point for their voltages. Generally referred to as common or ground, although it may not be actually connected with the earth, this reference remains at "zero volts" while other signal voltages "swing" positive (above) and negative (below) it. Physically, the common may be a wire, a trace on a printed-circuit board, a metal chassis, virtually anything that conducts electricity. Ideally it should be a perfect conductor, but in any practical system it is not. As the complexity and size of the system is increased, the imperfect conductivity of the common (ground) conductor inevitably causes problems.

Hum and buzz (50Hz/60Hz and it's harmonics) occur in unbalanced systems when currents flow in the cable shield connections between different pieces of equipment. Hum and buzz can also occur balanced systems even though they are generally much more

The cable shield currents and ground voltage differences are caused by several mechanisms. The second most common source of hum and buzz is the voltage difference between two safety grounds separated by a large distance or the voltage difference between a safety ground and an "Earth" ground (such as a grounded satellite dish or cable TV source). This problem is usually called "ground loop". This is the most common one in severe humming problems.

Hum and buzz can also be magnetically induced or capacitively induced directly into signal cables. Or the noise current can leak from mains input through capacitance between the A.C. power transformer primary and secondary windings which causes that a portion of the A.C. line voltage will ALWAYS be capacitively coupled directly to audio circuit ground. This capacitivly coupled power line signal will usually contain significant harmonics out to 1MHz or more. These signals will cause currents to flow in the cable shields thus adding this noise directly to the audio signal.

Why grounding without problems is do difficult?
Virtually all data and broadcast construction projects run into problems of grounding. These problems occur primarily because there is a conflict between issues of safety (ground- ing to prevent electrical shock) and electronic noise reduction (using "ground" as an electronic "dump" for noise and inter- ference.) These two uses are often not compatible and can sometimes be in direct conflict with one another. The ultimate purpose of good groundind scheme is he preservation and adherence to the safety aspects while obtaining the maximum noise reduction possible. That is not usually an easy task to do.

Why ground loop is a problem?
Ground loops are a mystery to many people. Even college-trained electronic engineers may not know what ground loops actually are. Engineers have either concentrated on power distribution (for the electric company) or on equipment that happens to plug in to the power distribution system. Not much thought has been given to power distribution and equipment as a single entity where ground loops arise.

Ground loops are the most common cause of AC line frequency hum in sound systems. Ground loops can be geenrally identified by a low hum (60Hz in the US, 50Hz in Europe) through the sound system. A ground loop in the power or video signal occurs when some components in the same system are receiving its power from a different ground than other components, or the ground potential between two pieces of equipment is not identical.

Ground loop is a common problem when connecting multiple audio-visual system components together, there is a good change of making a nasty ground loops. Ground loops commonly cause humming noise to audio signals and interference bars to picture. Ground loop makes the system sensitive to pick up interference from mains wiring which can lead to erratic operation of the quipments or even damages to the equipments. Some articles claim that wiring and grounding problems account for up to 80 percent of all power quality related problems related with sensitive electronic equipments like audio/video systems.

The audio/video and power industries have each designed their systems and equipment independently. As a result, there's a degree of incompatibility. Usually which is pwefectly adequate in power distribution and operation safety sense is not good enough for AV-systems. Ground loop interference problem is a consequence of this.

Always when operating with grounding issues remember that there is no absolute ground. There is a certain amount of resistance to electrical current between all grounding points. This resistance can change with humidity, temperature, connected equipment and many other variables. No matter how small, the resistance can always allow an electrical voltage to exist across it when there is any current flowing between those grounding points (and there is some current flowing almost always).

Audio-frequency groundloop problems are typically in the low millivolt range, so it does not have to be much interference in grounding system to cause problems in audio systems.

Remember that there is no absolute ground. There is a certain amount of resistance to electrical current between all grounding points. This resistance can change with humidity, temperature, connected equipment and many other variables. No matter how small, the resistance can always allow an electrical voltage to exist across it. The ground wires between wall sockets and power company transformers are not perfect conductors and neither is the shield of your coaxial video cable. If they were, ground loops would not be a problem. Effects of ground loop in video pictures are in the form of a black shadow bar across the screen or as tearing in the top corner of a picture. This is caused by different earth potentials in a system.
http://www.rane.com/note110.html
Quote:
Ground Loops
Almost all cases of noise can be traced directly to ground loops, grounding or lack thereof. It is important to understand the mechanism that causes grounding noise in order to effectively eliminate it. Each component of a sound system produces its own ground internally. This ground is usually called the audio signal ground. Connecting devices together with the interconnecting cables can tie the signal grounds of the two units together in one place through the conductors in the cable. Ground loops occur when the grounds of the two units are also tied together in another place: via the third wire in the line cord, by tying the metal chassis together through the rack rails, etc. These situations create a circuit through which current may flow in a closed "loop" from one unit's ground out to a second unit and back to the first. It is not simply the presence of this current that creates the hum -- it is when this current flows through a unit's audio signal ground that creates the hum. In fact, even without a ground loop, a little noise current always flows through every interconnecting cable (i.e., it is impossible to eliminate these currents entirely). The mere presence of this ground loop current is no cause for alarm if your system uses properly implemented and completely balanced interconnects, which are excellent at rejecting ground loop and other noise currents. Balanced interconnect was developed to be immune to these noise currents, which can never be entirely eliminated. What makes a ground loop current annoying is when the audio signal is affected. Unfortunately, many manufacturers of balanced audio equipment design the internal grounding system improperly, thus creating balanced equipment that is not immune to the cabling's noise currents. This is one reason for the bad reputation sometimes given to balanced interconnect.

A second reason for balanced interconnect's bad reputation comes from those who think connecting unbalanced equipment into "superior" balanced equipment should improve things. Sorry. Balanced interconnect is not compatible with unbalanced. The small physical nature and short cable runs of completely unbalanced systems (home audio) also contain these ground loop noise currents. However, the currents in unbalanced systems never get large enough to affect the audio to the point where it is a nuisance. Mixing balanced and unbalanced equipment, however, is an entirely different story, since balanced and unbalanced interconnect are truly not compatible. The rest of this note shows several recommended implementations for all of these interconnection schemes.

The potential or voltage which pushes these noise currents through the circuit is developed between the independent grounds of the two or more units in the system. The impedance of this circuit is low, and even though the voltage is low, the current is high, thanks to Mr. Ohm, without whose help we wouldn't have these problems. It would take a very high resolution ohm meter to measure the impedance of the steel chassis or the rack rails. We're talking thousandths of an ohm. So trying to measure this stuff won't necessarily help you. We just thought we'd warn you.
http://www.ethanwiner.com/dimmers.html
Quote:
Kill Studio Hum and Buzz at the Source

HUM 101

Hum derives from the fundamental frequency of the AC power line, which in the USA is 60 Hz. However, most hum also contains harmonics of that fundamental frequency: 120 Hz., 180 Hz., and so forth. In fact, the only real difference between "hum" and "buzz" is that buzz has more harmonics, and those harmonics extend to a higher audible frequency.

There are three basic ways that hum and other power line-related noises can get into an audio system. One is through radiation in the air, such as when you bring an electric guitar close to the power transformer in an amplifier. In this case the guitar's pickup acts as an antenna that receives the 60 Hz. energy being radiated by the transformer. The whole point of using shielding to surround the center conductor on guitar wires and studio patch cords is to keep radiated hum from impinging on the wire inside the shielding.

The second way hum can be induced into an audio system is when a voltage difference exists between the common ground connections of two or more pieces of equipment. Third, clicking and buzzing noises can get into an audio device through the power wires. Every time an electric motor is turned on or off, the motor's coils "kick back" into the power line a brief but high-level voltage spike. The large motors used in refrigerator and air conditioner compressors are a common cause of audible clicks and pops. The power supplies used in most audio gear are unable to block these high-frequency impulses, and they pass right through the power supply into the audio circuit.

Similarly, solid-state light dimmers can create havoc with audio gear. These devices work by changing the amount of time the full power line voltage is applied to the light being controlled, as opposed to actually raising and lowering the voltage. Although AC power is supplied by the power company as a pure sine wave (having no harmonics), the dimmer's sudden switching of the voltage on and off actually generates harmonics which extend to very high frequencies. And these high frequency harmonics can get into audio gear both by radiation through the air and also by traveling through the power wiring directly into the audio circuitry.
.
.
.
READ THE REST OF THE ARTICLE BY CLICKING ON THE LINK.







Jensen makes a high end isolator for subwoofers, but it is expensive.




Instructions For Xitel Isolator:










How To Install the Ground Loop Isolator?

Turn the power of your computer or audio component and home stereo system off. Plug the cable end of the ground loop isolator marked stereo directly into your stereo RCA input. Plug the RCA cable running from your computer or audio component into the RCA connectors on the ground loop isolator marked input. That’s all there is to it! No more ground loop hum!

The male cable of a ground loop isolator is the output. You normally plug them into the RCA inputs on the receiver and plug the source of the problem into the female side. If you find that the cable box is the source of the noise. You plug the cable box into the female side.

In the case of a subwoofer, the sub cable must go to the female side and the male side go to the sub amp. You may have to use Y adapters.

Noise & Hum Suppression Guides from Crutchfield:
http://www.crutchfield.com/learn/lea...de.html?page=2
http://akamaipix.crutchfield.com/ca/...oise_guide.pdf
http://www.crutchfield.com/learn/lea..._diagnose.html
http://www.crutchfield.com/learn/rev...ier_noise.html
http://www.crutchfield.com/learn/lea...ction_faq.html

PS3 Ground Loop Problems:
http://boardsus.playstation.com/play...read.id=844938
http://www.ps3-hacks.com/forums/about6545.html
http://www.avsforum.com/avs-vb/archi.../t-774745.html
http://www.highdefforum.com/archive/t-93027.html
http://www.procosound.com/download/w...t%20Cables.pdf
http://forums.afterdawn.com/thread_view.cfm/3/422586
http://www.answerbag.com/q_view/112686
http://nfggames.com/forum2/index.php...e;topic=3294.0
http://www.dvdtown.com/messageboard/topic/5197/2/
http://www.gamespot.com/pages/forums...ic_id=26321557
http://www.highdefforum.com/archive/t-85415.html
http://www.hdtvmagazine.com/forum/viewtopic.php?p=22232

Ground Loop Isolators (Read reviews):
http://www.thefind.com/instruments/info-ground-loop
http://www.amazon.com/s/?ie=UTF8&key...l_5oa76m1dpw_e
http://www.xitel.com/USA/prod_gli.htm
http://www.parts-express.com/pe/show...ewRand=8001739
http://www.tigerdirect.com/applicati...aCjCVqHCjCdwwp
http://www.radioshack.com/product/in...ductId=3445836
http://www.amazon.com/Ebtech-Hum-X-V..._bxgy_e_text_c
http://www.amazon.com/Xitel-GLI1-S1-...m_cr_pr_sims_t
http://www.amazon.com/Scosche-Eso34-...0709838&sr=8-4
http://www.amazon.com/Raptor-GL15-Gr...m_cr_pr_sims_t
http://www.amazon.com/3-5mm-Stereo-A...m_cr_pr_sims_t
http://www.amazon.com/Peripheral-PGL...m_cr_pr_sims_t
http://www.hdtvsupply.com/sistr.html
http://www.hdtvsupply.com/40428.html

High End Isolators:
http://www.ebtechaudio.com/products.html
http://www.amazon.com/Ebtech-HE-8-El...1660658&sr=1-6
http://www.jensen-transformers.com/sub1rr.html
http://www.jensen-transformers.com/ci1rr.html
http://www.jensen-transformers.com/ci2rr.html
http://www.alectrosystems.com/alectr.../Decoupler.htm

Ferrite Cores & Eliminating RF Interference:
http://store.solar-electric.com/nosufefi.html
http://www.k0bg.com/beads.html
http://audiosystemsgroup.com/Ferrites-Ham.pdf
http://www.hatdaw.com/papers/Generic_RFI_Handbook.pdf
http://www.w5qgg.org/marc/downloads/RFI-Ham.pdf

Reference Articles:
http://www.epanorama.net/documents/g...oop/index.html
http://oreilly.com/pub/h/4241
http://www.sweetwater.com/shop/cable...ying-guide.php
http://www.audioholics.com/tweaks/co...m-hum-and-buzz
http://en.wikipedia.org/wiki/Mains_hum
http://www.subwoofer-builder.com/earth-loop.htm
http://www.tomshardware.com/forum/39456-6-subwoofer
http://stereos.about.com/od/troubles...bwooferhum.htm

Last edited by Big Daddy; 03-04-2011 at 10:11 PM.
  Reply With Quote
Old 05-07-2009, 12:09 AM   #2
Big Daddy Big Daddy is offline
Blu-ray Champion
 
Big Daddy's Avatar
 
Jan 2008
Southern California
79
122
1
Default

What Causes a Subwoofer to Make a Noise?

A subwoofer can make a noise for many different reasons:
  1. Grounding problems: These can occur either because of loose connections or unshielded cables. The other reason is the ground loop problem. Read https://forum.blu-ray.com/home-theat...isolators.html.
  2. Voltage Spike: A voltage spike is another possibility. Use a good power conditioner and voltage regulator.
  3. Bottoming: Another possibility is that you are driving the subwoofer too hard and it is bottoming (i.e., the voice coil is hitting on the back of the magnet and making a noise). Turn the level down and calibrate the sub using the auto calibration program or an SPL meter.
  4. Port Chuffing: This is due to the flow of too much air through the port. This basically means that you are over driving the subwoofer or the subwoofer is not adequate enough for home theater needs. You can find more information on Port Chuffing in Post #2 of A Guide to Bass Management (Part II).
  5. Sometimes it is the AUTO ON feature of the subwoofer that is causing the problem. During extended periods when there is no LFE and sub activity, it is possible for the subwoofer to go into sleep mode. After some period, if there is some low frequency activity, the subwoofer may come back on and make a clicking noise. Turn off the AUTO ON feature and use the regular ON button and see if it helps.
  6. Blown Speaker Cone: This usually happens when the driver has a small hole in it. As a result, you may hear a pop everytime there is some bass in the audio signal.
  7. Amplifier: It is possible that the amp is ready to say good bye.
Useful Threads:
http://www.crutchfield.com/S-gXAyvVs...ech/kb350.html
https://forum.blu-ray.com/subwoofers...n-cranked.html
http://www.highdefforum.com/speakers...ing-noise.html
http://www.askautoinfo.com/discuss/c...24/page_1.html
http://www.avsforum.com/avs-vb/showt...6#post19214096
http://www.avforums.com/forums/blu-r...ay-player.html
http://www.stevehoffman.tv/forums/ar...p/t-68085.html
http://www.ehow.com/how-does_4969618...oofer-pop.html


Testing for Ground Loop Problems

http://www.siber-sonic.com/electronics/GLooptest.html
http://www.siber-sonic.com/electronics/DMMrecs.html
http://www.siber-sonic.com/electroni...tTestRead.html


Other Solutions for Audio Noise Problems

PS Audio Noise Harvaster, $99.95:
http://www.psaudio.com/ps/products/d...es-accessories
http://www.musicdirect.com/product/74135
http://www.audioadvisor.com/prodinfo.asp?number=PSHARV
http://www.crutchfield.com/S-h6F5qkw...er.html?tp=568



AudioPrism Quietline MKIII Filters, $40:
http://www.audioprism.com/quietline.html
http://www.musicdirect.com/product/74169
https://www.elusivedisc.com/prodinfo...ber=AP-QUIETL1




Reducing RF Noise with Ferrite Core Beads

http://www.antennex.com/shack/Dec99/beads.htm
Quote:
TV Sets. Put a bead or toroid on the power cord as it enters the set. Toroids or split beads on the antenna cable also may be needed.

VCR's. The VCR is a real RFI problem. Ferrite beads on all wires entering the VCR can eliminate RFI from most amateur bands. But on 80 meters even this doesn't always work. It may be necessary to shield the VCR housing to completely eliminate RFI.

Stereo. Long speaker wires can act like an antenna to pick up RF and feed it into the output of the amplifier. The amplifier's feedback circuit allows the RF to reach the input where it is rectified, amplified and then heard in the speaker. The solution is to use beads on the speaker wires just as they leave the amplifier. RF can enter the stereo system through the power cord. Use a split bead or a toroid on the cord just as it enters the stereo.

We have been talking about keeping RF out of equipment. You can also use beads and toroids to keep RF in. That fish tank heater that makes all that racket on 80 meters is using its power cord and the house power wiring to radiate interference.

A bead or toroid on the power cord right at the heater can keep the noise from entering the wiring. Computer power cords and connecting cables can be treated in the same manner. Sometimes RF comes out of a transceiver’s power cable. A toroid can stop it. Or RF flows on the outside of the antenna cable, going right around your lowpass filter. Again, toroids to the rescue.

Computers. Computers are a part of many modern amateur radio stations. Often they are directly connected to the transceiver for RTTY, packet and other digital modes. They also are used for contest scorekeeping and other uses. Computers generate RFI because they use digital waveforms in the high frequency band that have high harmonic content. They can cause interference throughout the shortwave band and even into VHF.

Some of the interference is radiated from the circuit boards but the most common source is interference conducted out of the computer on the many cables that connect it to its monitor, its keyboard, its printer, and the radio or its data controller interface.

To get rid of the interference, it is helpful to try to find which cable it's coming out of. Start by tuning in the interference and writing down the "S" meter reading. Then disconnect, one at a time the devices connected to the computer and as you do so note any change in "S" meter level. Disconnect the printer, the modem, the keyboard, the mouse, the monitor, the data controller, and anything else connected to the computer. Hopefully this procedure will give a good clue as to where the problem lies.

If you isolate the major problem to one external device, place toroid cores or split beads over the lead from the computer.

Do this right at the exit point from the computer. Also, if the affected device is itself an active generator, a monitor for example put beads right where the leads come out of it. Watch the "S" meter for any change - this tells you if you are getting somewhere. Also, if the device has a power cord or a telephone cord put beads on them. Always remember that telephone and power wires can conduct interference outside your residence and near your antenna.

Please feel free to contribute to this thread. Too many members are experiencing ground hum problems and sending me private messages. Tell us about your problems and the solutions you used to eliminate them.

Personally, I had a huming problem with my subwoofer cables. At the time, I was using standard RCA cables. Everytime I touched or moved the cables, I would hear a very loud hum from the subwoofers. I replaced the cables with RG6 subwoofer cables and the problem went away.

Last edited by Big Daddy; 08-07-2011 at 03:06 AM.
  Reply With Quote
Old 05-07-2009, 12:24 AM   #3
Johnny Vinyl Johnny Vinyl is offline
Moderator
 
Johnny Vinyl's Avatar
 
Jul 2007
At the crossroad of Analogue Dr & 2CH Ave
19
205
7
3
8
Default

Another great informational thread and I'm sure it's something that occurs quite frequantly. I personally don't notice any hum, but I might shoot over to RS or TD and pick one up to test out.

John
  Reply With Quote
Old 05-07-2009, 12:33 AM   #4
got rice got rice is offline
Senior Member
 
got rice's Avatar
 
Jan 2009
Default

Thanks BD... I'm with John(the Totem Guy ) fortunately, I haven't experienced this.

Curious, does the amount of current running through the system have anything to do with it?

I can remember when I had a Soundstream 1000watt amp in my car it had horrible issues with humming.
  Reply With Quote
Old 05-07-2009, 12:37 AM   #5
crazyBLUE crazyBLUE is offline
Moderator
 
crazyBLUE's Avatar
 
Aug 2008
Pacific Northwest
89
479
1
38
30
Default

All though I have not experienced any humming in my system ! If it ever happens I will know where to go !! Good idea Big Daddy ! As always .
  Reply With Quote
Old 05-07-2009, 01:26 AM   #6
Larsco Larsco is offline
Member
 
Dec 2007
Minnesota, USA
52
Default

I experienced the humming described about a year ago, and tried all of things recommended above regarding plugging and unplugging and moving things around, but nothing helped. So, I figured I'd share my experience and solution in case it helps someone out.

I discovered it was being caused by the cable line. When I disconnected the Comcast cable from the wall, the buzzing stopped. Of course, this wasn't a good permanent solution, since I want cable TV.

So, I tried a ground loop isolator as suggested above. I got one for about $10 online. It was designed to go right into the cable line, about the size and shape of a AA battery. This eliminated the humming, but caused some of the HD cable channels not to come in. Again, not a great solution because I want all the stations.

The final solution was to ground the cable line properly. I attached a copper wire to an upstream cable line splitter, and ran it to the pipe network in my basement. Problem solved! No humming, and all my channels now come in.

In discussing this situation with others, we decided it was Comcast's fault. I understand it is their responsibility to ground the cable locally when they perform the installation, which they evidently neglected to do.
  Reply With Quote
Old 05-15-2009, 01:09 AM   #7
SammyG SammyG is offline
Special Member
 
SammyG's Avatar
 
Feb 2009
Douglassville, PA
1034
7
Default

Quote:
Originally Posted by Larsco View Post
I experienced the humming described about a year ago, and tried all of things recommended above regarding plugging and unplugging and moving things around, but nothing helped. So, I figured I'd share my experience and solution in case it helps someone out.

I discovered it was being caused by the cable line. When I disconnected the Comcast cable from the wall, the buzzing stopped. Of course, this wasn't a good permanent solution, since I want cable TV.

So, I tried a ground loop isolator as suggested above. I got one for about $10 online. It was designed to go right into the cable line, about the size and shape of a AA battery. This eliminated the humming, but caused some of the HD cable channels not to come in. Again, not a great solution because I want all the stations.

The final solution was to ground the cable line properly. I attached a copper wire to an upstream cable line splitter, and ran it to the pipe network in my basement. Problem solved! No humming, and all my channels now come in.

In discussing this situation with others, we decided it was Comcast's fault. I understand it is their responsibility to ground the cable locally when they perform the installation, which they evidently neglected to do.
I'm having this exact problem, isn't there an easier way to fix it?
  Reply With Quote
Old 05-15-2009, 02:08 AM   #8
Larsco Larsco is offline
Member
 
Dec 2007
Minnesota, USA
52
Default

You should be able to call your cable company, tell them that your cable line isn't properly grounded on-site, and describe your symptoms. They should acknowledge that it's their mistake and come back out and properly ground the cable. I believe this is typically done where the cable enters the house.

Alternately, in my research about the problem, it seems that the "loss of channels" due to the ground loop isolator doesn't necessarily effect everyone everywhere. It might be worth a try.
  Reply With Quote
Old 05-15-2009, 02:10 AM   #9
D D is offline
Blu-ray Ninja
 
D's Avatar
 
Feb 2008
Roaming the Highlands
1
1
Default

You can also use two 75 ohm transformers, the type with a threaded female F-connector on one end, and a Y with spade connectors on the other. Cut off the spades, and splice the wires of the Y's together so the transformers are connected together. Put them inline with your cable feed. Should take care of the ground issue, for no more than a few bucks at radioshack.
  Reply With Quote
Old 05-15-2009, 02:18 AM   #10
vega2K vega2K is offline
Blu-ray Samurai
 
vega2K's Avatar
 
Jan 2009
68
345
228
Default

Big Daddy,

I am always amazed at your resourcefulness and your willingness to share your knowledge. Your a great role model. Thank you.
  Reply With Quote
Old 05-15-2009, 08:35 AM   #11
Big Daddy Big Daddy is offline
Blu-ray Champion
 
Big Daddy's Avatar
 
Jan 2008
Southern California
79
122
1
Default

Quote:
Originally Posted by vega2K View Post
Big Daddy,

I am always amazed at your resourcefulness and your willingness to share your knowledge. Your a great role model. Thank you.
Thank you. I try my best to help others. I hope I am successful.
  Reply With Quote
Old 05-15-2009, 11:57 AM   #12
Fors* Fors* is offline
Moderator
 
Fors*'s Avatar
 
Jan 2009
Pottstown, PA
160
12
142
11
Default

Quote:
Originally Posted by Big Daddy View Post
Thank you. I try my best to help others. I hope I am successful.
Most of the time you are Big Daddy, and I truly appreciate it.

By the way, I had the same issue with Comcast as I had hum and found out the cable wasn't grounded. I also ran copper wire to some pipes I had (my TV is located in a finished basement, so this was very easy to do for me). I usually always try to watch these guys when they mess with my cables, as it seems this happens quite a bit.
  Reply With Quote
Old 05-15-2009, 12:53 PM   #13
BACsader BACsader is offline
Expert Member
 
BACsader's Avatar
 
Jan 2008
Cooper City FL
29
72
9
1
Default

Right now I am experiencing this and have done a lot to get rid of the problem. I experience it when I have the volume up on all of my electronics such as DTV, PS3, and my Standalone Blu-ray player. I have bought an home theater Power Conditioner and that removed a lot of the noise but not all. The hum comes from the device that I am using. For instance, if I am watching a Blu-ray and disconnect that HDMI cable, the noise goes away.
  Reply With Quote
Old 05-15-2009, 04:38 PM   #14
repete66211 repete66211 is offline
Blu-ray Samurai
 
repete66211's Avatar
 
Jan 2009
Kansas City area
10
196
1
3
Default Sub hum

I experience a slight buzz from the sub, but not all the time. I haven't nailed down exactly when it's there and when it isn't, but I know I heard it when watching the Grapes of Wrath DVD (mono) and Kagemusha (listed as 2.0, but PS3 display read 4.0). I haven't tried unplugging any devices to isolate the source since the buzz doesn't occur frequently.

Could it possible the sub will buzz only when there's no LFE signal?
  Reply With Quote
Old 05-15-2009, 11:41 PM   #15
Big Daddy Big Daddy is offline
Blu-ray Champion
 
Big Daddy's Avatar
 
Jan 2008
Southern California
79
122
1
Default

Quote:
Originally Posted by repete66211 View Post
I experience a slight buzz from the sub, but not all the time. I haven't nailed down exactly when it's there and when it isn't, but I know I heard it when watching the Grapes of Wrath DVD (mono) and Kagemusha (listed as 2.0, but PS3 display read 4.0). I haven't tried unplugging any devices to isolate the source since the buzz doesn't occur frequently.

Could it possible the sub will buzz only when there's no LFE signal?
A normal sub that is not broken or malfunctioning should not make a buzzing noise.
  Reply With Quote
Old 05-17-2009, 05:19 AM   #16
repete66211 repete66211 is offline
Blu-ray Samurai
 
repete66211's Avatar
 
Jan 2009
Kansas City area
10
196
1
3
Default

Quote:
Originally Posted by Big Daddy View Post
A normal sub that is not broken or malfunctioning should not make a buzzing noise.
I've isolated the problem. The buzzing does not occur while watching stereo or surround sound [HD cable] TV. It only buzzes, and then only faintly, when the audio source is a movie on the PS3. Strange.
  Reply With Quote
Old 05-17-2009, 07:34 AM   #17
aramis109 aramis109 is offline
Blu-ray Ninja
 
aramis109's Avatar
 
Mar 2008
Milwaukee, WI
10
4
360
18
Default

Quote:
Originally Posted by repete66211 View Post
I've isolated the problem. The buzzing does not occur while watching stereo or surround sound [HD cable] TV. It only buzzes, and then only faintly, when the audio source is a movie on the PS3. Strange.
Try getting your PS3 power cable away from the other cables. Could be the interference is originating in the PS3.
  Reply With Quote
Old 05-18-2009, 04:20 PM   #18
repete66211 repete66211 is offline
Blu-ray Samurai
 
repete66211's Avatar
 
Jan 2009
Kansas City area
10
196
1
3
Default

Quote:
Originally Posted by aramis109 View Post
Try getting your PS3 power cable away from the other cables. Could be the interference is originating in the PS3.
Unfortunately that isn't possible with my current setup, at least not until the APC H15 goes on sale again and I can scrape enough cash together for a better entertainment center. As I have it now all power cords and speaker cables run out of a 2" hole in the back of my TV stand. I know, less than ideal.
  Reply With Quote
Old 05-18-2009, 04:29 PM   #19
Fors* Fors* is offline
Moderator
 
Fors*'s Avatar
 
Jan 2009
Pottstown, PA
160
12
142
11
Default

Quote:
Originally Posted by repete66211 View Post
Unfortunately that isn't possible with my current setup, at least not until the APC H15 goes on sale again and I can scrape enough cash together for a better entertainment center. As I have it now all power cords and speaker cables run out of a 2" hole in the back of my TV stand. I know, less than ideal.
Is there enough room in that hole to possibly "insulate" the PS3 cable and prevent the interference? Just throwing this idea out there...not even sure if it would work....but perhaps it could?
  Reply With Quote
Old 05-18-2009, 04:45 PM   #20
repete66211 repete66211 is offline
Blu-ray Samurai
 
repete66211's Avatar
 
Jan 2009
Kansas City area
10
196
1
3
Default

Quote:
Originally Posted by forsberg21 View Post
Is there enough room in that hole to possibly "insulate" the PS3 cable and prevent the interference? Just throwing this idea out there...not even sure if it would work....but perhaps it could?
No there isn't, but even if I did I would still have to plug it in right next to some other power cords. Or are you suggesting the PS3 power cord is interfering with the subwoofer cable? I hope not. (BTW, switching my Blue Jeans sub cable with my old Monster THX cable had no effect.) I suppose I could cut a larger hole in the back of the TV stand.
  Reply With Quote
Reply
Go Back   Blu-ray Forum > Home Theater > Home Theater General Discussion

Similar Threads
thread Forum Thread Starter Replies Last Post
Help with pop and then ground loop Audio Theory and Discussion Intamin 7 11-18-2009 12:50 AM
Buzzing sound from my speakers (Ground loop problem) Home Theater General Discussion Rike255 1 09-20-2009 06:11 AM
Noisy Onkyo 605...ground loop/RFI Receivers VinnAY 23 12-07-2008 02:26 PM
What's the Ground Doin' Shakin' General Chat phloyd 3 10-31-2007 08:53 AM


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 10:19 PM.