HUM FAQ, by Bill Lummus (Beta version)

Does your system hum? Here is some basic information and a troubleshooting algorithm

How do I figure out what is causing the problem?

1. Disconnect everything from the amp except the power cord and the speakers. Do you still have the hum? If so, see number 2

2. Disconnect everything from the preamp but connect the preamp to the amp and plug them both into the same outlet. Do you have the hum now? If so, see number 2

3. One by one connect each source to the preamp. When you hear the hum you’ve localized the problem. What is most common is that when you connect a source that has any connection to the video system (like a DVD player connected to the TV or a cable box) then the hum will appear. Go to 1.

NOTE: optical interconnects are immune to ground loops and EMI/RFI.



1. Ground loops

Most common in the home theater environment is a ground loop. What is a ground loop? Simply put, it is when the ground currents have more than one path from the component to earth ground. This is most severely and most commonly cause by having two separate grounds. One main electrical house ground and one for the CATV, antenna, satellite, etc… This can result in a safety hazard at worst and some nasty current flow and noise at best. Usually this is manifested as a low pitched 60 hz hum.

Tuner box----------------------CATV/SAT ground
|
TV
|
DVD Player
|
Pre/Pro
|
Amp------------------------------House Ground

You can see that if the two grounding points are at different potentials you will get current flow through the system and noise.

Systems with a properly unified ground can also have ground loop hum simply because the impedance of the different roads to ground are different.

Different equipment can have dramatically different sensitivities to ground loop current. Very powerful amps, amps with high input sensitivities, amps with high input impedances, and systems with very sensitive speakers will all be very sensitive to ground loop hum. Other types of systems may not be so sensitive. This is why a system which has never hummed before can hum when a component is added or changed. It may be that a ground loop was created, or it may be that an existing ground loop is now noticeably audible.

The solution?

A. The best solution is to unify the grounds in your system. First and foremost be sure your CATV/SAT/ANT is properly grounded to your main house ground. You can find your main house ground next to your utility meter. It’s a copper rod driven into the ground and it has a large gauge copper wire connected to it. You can run a wire from the splitter for your video source to this grounding rod. All the ingredients are available at your local hardware store, Home Depot, or Lowes. Frequently this will solve the hum. If you don’t feel like doing this yourself, call you cable or satellite installer. It’s code- they are supposed to do it correctly.

It is important for safety reasons to have all the grounds bonded together. Say, for example, a bolt of lightning struck the earth near your service entrance. This is going to cause a large voltage surge at the ground. As long as everything is connected and bonded to that ground- no problem. There will be no difference in voltage and no current over the systems in your house. But if you have a CATV or satellite dish ground somewhere else you have a problem. That ground is going to be at a dramatically different potential than your main house ground. Guess what those grounds are connected through… your equipment! Now you have a surge of up to 6000 volts traveling from one ground site to another through your house and equipment. Equipment damage is likely and you or your family could be injured or killed. “Cheater plugs” are OK for troubleshooting and testing, but should not be used for a long term solution.

B. Now that everything is grounded properly we can proceed to other possibilities. Remember that ground loops can propagate even if everything is grounded properly. All that is needed is more than one path from your equipment to the grounding point. One solution is to plug everything into the same outlet. If you demand on having more than one outlet for your system, you may need one of the ground loop isolators. These are isolation transformers which break the ground loop without affecting the sonics. There are several available. Probably the most famous are from Jensen transformer and they have excellent white papers about proper grounding and system hum available on their website.

C. It can happen sometimes that a particular component (audio or video) will dump a lot of noise on the safety ground. If you connect everything back one by one and, for example, when the TV is brought into the loop the hum appears. But you disconnect the CATV/SAT from the wall and the hum persists then this is probably the case. See B above for solutions.



2. You could be having a problem with EMI/RFI, you could have a power problem, or you could have a defective component.

EMI/RFI usually has more of a hiss quality than a deep hum.

A. Use shorting plugs on every unused input. EMI can enter your system over unused RCA or XLR inputs. You can buy shorting plugs at various location, or you can make your own by soldering the center pin to the grounding pin on cheap RCA connectors. If you need to short unused XLR plugs, check with the manufacturer. DO NOT SHORT THE OUTPUTS- you will damage the equipment.

B. Be sure to use shielded interconnects. Unshielded interconnects are very susceptible to ambient noise.

C. If you do all this and it still doesn’t help, next is to troubleshoot power problems. Unfortunately, there is no easy way to do this. A lot of household appliances dump noise on the power lines. Most notorious for this are halogen lights and dimmer switches- both commonly used in HT construction. You can take the equipment to another part of your house and hook it up to see if the problem persists or you can just carry it down to you local HIFI shop and have them plug it in, If the hum goes away with the equipment in another location- you have a problem with your power source. Power conditioners may or may not help. You may need an isolation transformer, balanced power, or a power regenerator.

D. If the hum is there no matter where you plug it in, you could have a defective component. Take it back to where you bought it or send it back to the manufacturer to be tested. You could also have a very sensitive system and just be hearing the noise floor of your equipment. This is a more common problem with 100+ dB sensitivity speakers.

If you still can’t figure it out, post a message.




This is a beta version, please send me a private message with suggestion for improvement, do not post them here!

Question:

The most common ground in an A/V system is the third wire in the power circuit, which ties back into the main distribution panel. On mine it and the neutral (white) on 120V circuits both meet at the neutral bar.

Should the neutral bar tie directly to the house ground stake?

How does one prove that to be a solid connection?

I don't get it.
First you disassemble the entire system.
Then, if the amp still hums I add the preamp?

Why not start by:
Disconnect the video (cable, sat, etc).
If the hum goes away, the cable needs to be grounded.
If not,
Disconnect the sub.
If the hum goes away . . . is the sub on a different circuit, if so we found the problem.
If we still have hum and it is not from the two most common sources,
Then
Turn off all the sources (DVD player, cd player, etc.).
If the hum is gone, turn them on one at a time until it comes back.

If there is still hum with all the sources turned off, then disconnect them.
If the hum goes away, add them one at a time until it comes back.

Otherwise, if there is hum with only the pre and power amp connected:
disconnect the pre. If the hum goes away, it is the preamp.
If you still have hum, the amp is bad

Thanks for this Bill. Much appreciated:

http://www.avsforum.com/avs-vb/showthread.php?s=&postid=3369955

:)

Very timely for me .....

Hey - I have a halogen lamp that makes my amp humm when it's in the dimmer mode (at full lighting, everything is fine - no hum). Would one of those Tripplite Isobars w/ their isolated power banks be able to correct this?

Just a quick note on ground loops caused by cable. If you do not want to wait, or you cannot get your cable company to come and ground your cable properly, it is very simple to do.

First you should have one of these (http://www.partsexpress.com//pe/showdetl.cfm?&User_ID=16088947&St=1227&St2=-57184423&St3=72579927&DS_ID=3&Product_ID=2245&DID=7) where you cable comes in to your house (usually where all utilities, electric, telco, etc.) come in. If you do not, then get one. Next you will ground this to your house ground (cold water pipe or rod) you will see your telco and electric breaker box attached to a place on the cold water pipe or rod, just tie into one of these or get another clamp. That is it, you are done.

If your cable is grounded but you do not see where it is grounded to, just change it to the same place as the rest of your house, no more ground loop.

I know this was stated above, but I though I would help out just a bit. I have included a diagram for those that would like.

As for halogen lamps, move them to a different room on a different circuit or get a different lamp. If you have AC buzz, either run a dedicated circuit, or if that is not possible, try an isolation transformer (http://www.tripplite.com/products/conditioners/transformers.cfm).

So the regular Tripplites won't cut it, huh? Guess it might be time to find a better halogen.

I have my doubts as to if they will take care of it fully, they may help. I moved my halogens to a different room. I have not found a halogen that did not add AC noise. Chokes are not as good with extremely noisy devices as these lamps are, isolation of the electronics from the noisy source is they way to cure it. The isobars use chokes and do not truly isolate. You may cut it back some, but I think you will still hear it.

Time to get a non-halogen. :D

Originally posted by DMF
Question:

The most common ground in an A/V system is the third wire in the power circuit, which ties back into the main distribution panel. On mine it and the neutral (white) on 120V circuits both meet at the neutral bar.

Should the neutral bar tie directly to the house ground stake?

How does one prove that to be a solid connection?


DMF:

With some panels, your neutral and your ground can be on the same bus bar. Thus, your ground/neutral bus bar will connect to the ground (rod or cold water pipe).

You can use a simple plug-in circuit tester (http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=22-141) that will test for ground. You can purchase these at home improvement centers, electronic stores, etc. If the outlet you check passes the ground test and your cable feed is tied to the same ground. You are most likely grounded properly.

Thanks Dr Spike! Any suggestions for a replacement lamp? Should I go for say, a flourescent lamp?

Fluorescent can cause AC noise as well, although they tend not to be nearly as bad as halogen. I have had fluorescent on the same circuit with no problem. You could try one. Incandescent is always a good choice, always nice and quiet.

Originally posted by DrSpike69
You can use a simple plug-in circuit tester (http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=22-141) that will test for ground. ... If the outlet you check passes the ground test and your cable feed is tied to the same ground. You are most likely grounded properly.
"A "Must" for power tool users and musicians"

Well, I do use power tools...

Yes, I've got one of these, and use it for polarity etc... But how does it check for a relationship between ground/neutral and a water pipe?

It will tell you if you have an open ground in what you are testing, if all your outlets come out with an open ground you have an open ground. Best way is to physically look and see if your power main, cable, and telco are connected to the common ground. To see if you are properly grounded you can check the ground impedance, it should be 25 ohms or less.

Okay, I can see that. No current flow, no path to ground.

One of these days I'll pull the panel and check neutral bar to water pipe. (I don't have any ground loops or other wierdness, just trying to understand how to diagnose someone else's future problem. Thanks.)

No ground loops, sounds like you are in great shape. :) The panel is easy to come off, just be careful not to touch certain areas, even if you turn the main breaker off, the box is hot. You can also get a good zap if you touch the neutral bar and become the ground for a circuit. For the most part, I have always added circuits with the mains left on. I was taught that way, probably not the safe way. :) I guess the safe way is to have the power company shut off your power. Unless you have a breaker by the meter, not all places do.

Glad to shed some light on the subject.

place a .15uf cap and a 1.5k resistor in parallel across your volt meter leads then check for leakage by grounding the black lead and touching the red lead to metal on the chassis.

I've been racking my brain for about a week now trying to get rid of the hum in my subwoofer... Hopefully someone has some ideas.

I have a SunFire subwoofer hooked up to an Integra DTC 9.4.

So far, this is what I've tried...

I've disconnected everything and found that the "hum" doesn't appear until I hook up the cable from my PreAmp to my subwoofer. Then it doesn't go away until I unplug the RCA cable. If I plug the Subwoofer in without the cable, I get no hum. But once I plug in the cable, there's the hum...

Any ideas how to fix this?

Please don't post on this thread. Start another one for individual issues. This would get overly cumbersome if everyone jumped in.

While running a link checker on my PC, I found that certain links no longer existed. Well that's fine as I tend to overbookmark anyways. However a good one regarding Ground Loops was gone. Turns out there's a site that actually archives old sites...well a lot of them anyways. Typing in the old URL into the WayBack Machine resurrected what I think is a pretty good and informative article. If you've got some spare paper on the printer, this is one of those keepers that provides a good background, plans for the GL elimination, and still has some nice, informative graphics to illustrate points. For anyone whose interested, just click here. (http://web.archive.org/web/20010619181146/http://www.securityaudio.com/groundloops.htm)

Update on other sites that also have information regarding hum.

Ground loop problems and how to get rid of them (http://www.epanorama.net/documents/groundloop/index.html)

Ground Loops or Let Me Hum a Few Bars (http://smr-home-theatre.org/Ground-Loops/)

FAQ About Ground Loops with Frequently Given Answers (http://www.elect-spec.com/faqgrdl.htm)

Ground Loops What They Really Are (rescued via the internet archive site) (http://web.archive.org/web/20011211074810/http://www.vac-brick.com/1994grnd.html)

Balanced Line Technology (rescued via the internet archive site) (http://web.archive.org/web/20030410190419/http://www.dself.demon.co.uk/balanced.htm)

I noticed a ground hum/loop I dont know what to call it but I notice that when I grab the end of the coax wire that comes in to my house with one hand and the coax wire that goes to my HT with the other I get a little buzz in my hands(these two wires are normally connected via a splitter). If I took the wire that runs to my HT a ran that through the coax inputs on my Monster HTS 5100 would that solve my buzzing problems?

Daniel Smith

Once again- please don't post specific issues to this thread. Start your own individual thread.

If you have something like Chu added- this is the place.

If you want to work in your circuit breaker box but would like none of it hot, you can remove the meter outside of your house.

1) Turn off all sensitive equipment (computers, etc).
2) Go to breaker box, turn off your main breaker.
3) Go to your meter box outside, open it up and remove the meter.
4) Do your work in the breaker box.
5) Once done, double check to make sure that your main is still off.
6) Replace the meter outside.
7) Flip your main back on.

If you have any large loads that are still on while you are working, you should turn those circuit breakers off one-by-one before step 2. And then turn them back on one-by-one after step 7.

Is a shorting plug the same as an AC ground floater? Another website (Audiovideorevoluton.com) recommends using AC ground floaters on each of your components until you find the one with the hum, then leaving the floater on that one component. That worries me though, because I thought that AC ground floaters just remove the ground and leave you with an ungrounded connection. Any thoughts on this?

I hope this general query conforms to this thread. Feel free to delete it if it does not.

A shorting plug and a ground floater are not the same. A shorting plug is most like a jumper between signal and ground. A ground floater is a "cheater plug" which lifts the AC safety ground.

I don't mind so much the use of cheater plugs for troubleshooting purposes, but don't leave them there. It is called the "safety" ground for a reason.

What are your thoughts on isolated grounds? Isolated grounds run to seperate grounds? If the seperate grounds are all good deep grounds (8' rods or burried copper water mains) in different places around the house perimiter does this present a potential difference and a pos. hazard as in the lightning strike scenario? Should these seperate grounds be bonded together if they are used? Does the point of connection to the ground system matter? ie. Connecting cable ground block wire to an outlet ground with your av equipment vs. running it back to the ground rod.

Thanks for this thread.
-noam

All grounds must be bonded together. It's code. It's the law. Once they are bonded together it doesn't really matter where they are, as long as there is one at the service entrance where N-G bonding occurs.

Yes- there is a risk to you and your equipment if this is not done properly.

Re: CATV grounding. Always be sure there is a grounding block at the service entrance that is properly grounded. As long as this is present feel free to connect additional grounding blocks as you choose. I would connect them to the chassis ground of your equipment rather than an outlet. If the wire inadvertently connected to the hot wire from the outlet you'd have a problem!

Originally posted by Bill Lummus
All grounds must be bonded together. It's code. It's the law. Once they are bonded together it doesn't really matter where they are, as long as there is one at the service entrance where N-G bonding occurs.



It goes a loooong ways towards eliminating ground loop(hum) problems also.


Jim

If the cable company came to your house and put a ground rod in the ground and that is it, that is not considered a ground. If they came to your house and split bolted to your utility ground or a pipe clamp to your water main that is a true ground. But if a sat installer or a cable installer ever come to your house and put a copper rod in the ground it is not a ground. Tell them to get back out there and fix it. The only exception to this is if they run a #8 bare wire underground and no more then 20 ft to the main ground or else they have to ad another ground rod and go another 20 ft or less until they reach the utility ground.

OH AND THE CODE CHANGES FOR EVERY STATE. SO IF ONE GUY SAYS ITS CODE WHERE HE LIVES DOES NOT MEAN IT IS CODE WHERE YOU LIVE.

If the cable company came to your house and put a ground rod in the ground and that is it, that is not considered a ground. Not when it is a 4' rod no matter WHO installs it!

A eight foot rod, buried away from the house eight feet below ground as far as possible (at least a foot) with the heaviest gauge cable you can muster is a REAL ground!

I have had a passive subwoofer for sometime but haven't used it as I have not had a spare amp to power it. However, I have recently got my hands on a power amp which is powerful enough to do the job. The problem is that I get a hum is the rest of my speakers when I connect this amp to the sub pre-out on my av amp. This occurs only when a power supply is connected to the power amp even when it is pluged into the same outlet as the av amp. Does anyone have an ideas as to a solution or should I get another power amp.

Just to add a note here on 12 V remote triggers. This was the problem on my setup. I have a B&K Ref 50 and the 12 V trigger to the B&K amp caused about half of the noise.

The other half was caused by a Parasound Scamp that I was using to remotely turn on the subwoofer amp.

So when you are looking for sources, especially with subs, don't forget to look here.

And also note that if you have your speakers cutoff at 80 Hz, the only place you will really hear the hum is from your sub since the hum is a relatively low frequency (60 Hz?) signal.

Hum & Buzz in Unbalanced Interconnect Systems (http://www.audiovisualdevices.com.au/downloads/jensen/an004.pdf) is a rather short pdf download.

I have Athena sub which has slight hum. This is regardless of the input connection. Even after I moved the sub to another power outlet, the hum is still there. It is minor but if there is a way to silence it, I would like to know.

Since this is my first experience with any kind sub, I am not sure if they all do that.

- Vikas

I tried to post a message on this but somehow failed. You should add info that "speaker wire" should not be used to route a preamp level subwoofer signal from a source to a subwoofer. The wire needs to be shielded against pickup of 60 Hz from the house wiring! Speaker wire acts like an antenna, picking up enough 60 Hz to cause highly audible hum in the subwoofer. I have seen many postings addressing this question but no replys concerning shielded cable. My hum ceased when I disconnected the "Speaker Wires". It did not come back when I connected 25 ft of shielded (monaural) cable to the subwoofer. When I touched the "bitter end" of the shielded cable the hum returned (I became the antenna for a moment). When I connected the "bitter end" to the subwoofer drive I got zero hum (even with the subwoofer gain turned to max)! My problem is solved and I would like to try to help those who have simply used the wrong kind of wire to hook up the subwoofer. Based on the postings I have seen, a lot of folks are using "speaker wire" for this application....it is not a good idea! Thanks, Henry

Although my audio is fine from my AV reciever, I'm having a "video hum" problem. I was told it was probably similar to an "audio hum" problem and was directed to this thread for possible help.

I was using my InFocus 7210's DVI/MA connection from my DVD/scaler combo and the picture was great, but I found that a lot of DVDs needed help from the PJ's noise reduction feature. Also wanted the option of using the PJ's various "widescreen" settings for 4:3 movies.

Now I've changed to a direct component connection between the DVD player & PJ (Beldon 1694a cables). I did this to enable the PJ's controls for adjusting color, noise reduction, chroma & luma detail, etc...

Now, with my component connection I'm noticing a faint, slowly upwards scrolling "white horizontal line" across the screen. Also, all of the individual mirror/pixels seem to flicker (white) more now than they did with the DVI DVD/scaler combo connection.

Are these "video hum" symptoms of just bad component cables?
An audio grounding problem?
Another AC appliance?
Or just inherent of the component connection?

I didn't have have these video problems with the DVI & DVD/scaler combo, but that setup bypassed the PJ's processing and didn't give me control over some of the settings I wanted to adjust.

My simple left & right channel audio is wired the same no matter which of these 2 video connections is used (DVI or component). It just goes from the DVD player directly to the reciever and sounds fine. No audio hum. The only problem is the "video hum" with the component connection.

Any help would be greatly appreciated.

Look Here

http://www.21best.com/21_best/electronic/security/video/filters/for_sale_.html#HUMplug

I used a "hum eliminator" purchased from a local music supply store ($50). It was a 3 minute installation, ground loop buzz/hum problem solved. No rewiring, dedicated lines, connecting components by wiring screws, nothing. Outputs in via rca, and out via rca-to-XLR to Amp. simple and easy. I've seem many products like this that are all around the same price point. Mine was called "buzz off." I'm surprised the first solution seems to always be some kind of rewiring or connecting components in a MacGyver way when I found this simple solution in the music world for the same problem.

First you should have one of these (http://www.partsexpress.com//pe/showdetl.cfm?&User_ID=16088947&St=1227&St2=-57184423&St3=72579927&DS_ID=3&Product_ID=2245&DID=7) where you cable comes in to your house (usually where all utilities, electric, telco, etc.) come in. If you do not, then get one. Next you will ground this to your house ground (cold water pipe or rod) you will see your telco and electric breaker box attached to a place on the cold water pipe or rod, just tie into one of these or get another clamp. That is it, you are done.
isolation transformer (http://www.tripplite.com/products/conditioners/transformers.cfm).
Be aware that all ground blocks are not the same. Cable and satellite systems have different requirements and should be consulted before changing or adding a ground block.

I would also advise that you ignore the option offered above of grounding to an existing clamp that is already in use unless you think a new $2 clamp is worth giving your life for. NEVER undo an existing ground clamp unless you are professionally trained!

Also, many installers think that grounding to any cold water pipe is acceptable. It's NOT. It can only be the water main within 5' of entering the home IF it is an all metal under ground pipe for at least 10' after it exits the home. If you see a ground on a water pipe other than described you should have it corrected ASAP.

Hi,

I have a hum problem that I haven't been able to solve. First, my apartment had fluorescent
fixtures and when I turned on a switch you could hear a click or hum coming out of the speakers. After this, I replace all the lights in the apartment with regular bulb lamps. This presumably fix the problem for some time..
Second, I had a backlight (the one from cinemaquest with an RFI switch. The switch introduced some noise to the video so I switch it to a different place and is now gone.
Third, I installed a pure AV 60 line conditioner to the system and apparently the noise was gone for some time. After several months the noise is back again... And I really don't know what to do.. In the past I tried going through the isolation transformer route and didn't work out..All of the cables are of high quality, they are the MOnster THX ULTRa cables....


My guess right now, is that the speakers are very sensitive. How can you deal with this?

Or sadly, a component could be faulty? But how do u determine which?

Thanks

Hi,

I just moved from 1 house to another. In the new house, my system setup did not change at all. In both houses, all my components were one 1 wall plugged into an ADCOM power filter while my monitor and HD TiVo were on another wall plugged into a Monster surge protector.

After the D TV guy game and installed the new dish, I could hear a low hum through my speakers when the system was not turned on. I followed the steps listed in the FAQ and determined that when I unplugged a S Video cable from the back of the TV that connected to my pre amp, the hum stopped. The HD TiVO is connected to the monitor using component video and connected to the pre amp using ToS, a digital audio switching box and a digital coaxial cable.

I checked the dish and, sure enough, it was not grounded at all. I called D TV and they relocated the dish to within 10 feet of the common house ground. I cockily plugged everything back in and (gasp) the hum remains. I even tried unplugging and replugging with the proper amount of humility, but it still hummed!

So, as you can see, I need a little help. I'm confused as to why the exact same set up, connections and equipment would suddenly produce the hum when, for the last 6 years, it has been flawless.

Thanks for the help.

Are any of the 8 conductors in a CAT-5 ethernet cable conected to ground? If I have an ethernet port on my computer that has a sound card connected to my receiver, does connecting the ethernet cable to the network create an additonal ground path?

Just to add a note here on 12 V remote triggers. This was the problem on my setup. I have a B&K Ref 50 and the 12 V trigger to the B&K amp caused about half of the noise.

The other half was caused by a Parasound Scamp that I was using to remotely turn on the subwoofer amp.

So when you are looking for sources, especially with subs, don't forget to look here.

And also note that if you have your speakers cutoff at 80 Hz, the only place you will really hear the hum is from your sub since the hum is a relatively low frequency (60 Hz?) signal.

How did you fix the problem caused by 12V remote triggers? I have a power amp connecting to the pre-outs of a receiver. It worked fine until I use the 12V remote trigger.

How do I get rid of the hum in this case?

Yipee... my first hum problem. After installing a new component to my system (Buttkicker), I noticed noise in my speakers I never had before. After realizing it went away after unplugging th Buttkicker, I thought I had a faulty one....not so fast. Further investigating, I noticed out of all my components, the Buttkicker was the only device that had a ground plug, all of which is plugged into my monster power surge protector. Well it turns out after disconnecting the Cable to my HT, the hum went away. Im convinced now that the problem is the Cable and not the Buttkicker... I believe by the Buttkicker being the first device that has the third plug it simply unmasked the problem...... It also improved it slightly to not run the Cable line through the Monster bar, but directly to the Cable box. Now what do I do????? The Cable is grounded outside to the Electric meter and the house is grounded to the Water pipe..... Any suggestions?????????????????? Thanks.

Try a DC blocker, or ground breaker, on the incoming cable TV line.

Example at the bottom of the page at the below link.

http://www.hometech.com/video/atten.html
RF Attenuators, Filters, & DC Blockers - HomeTech Solutions

thanks!!!

I've run into a problem with speaker buzzing and I'm not sure on the cause. I've done a bit of reading up on it but am pretty bad in the audio field.

I have a cable box, xbox 360, and DVD player hooked up to my Samsung HL-S6187 TV and Yamaha HTR-5860 receiver.

Recently I hooked up my PC to the TV, and the sound to my receiver. I now get the buzzing sound out of all my speakers only when I am on the PC input.

Another thing that may be causing the issues is that I have the PC across the room, and the audio is run through a 3.5mm to RCA stereo converter and then through 25ft Red/White analog stereo cable to the receiver. Could this cable length be the problem or am I likely at the mercy of a ground loop or something of that sort?

I am having the same problem with humming that I can't figure out. I have a HK AVR 340 and I have run a 35' RCA cable from my mini-out on my computer to the reciever. The cable runs by one surge protector, my computer speakers subwoofer, and then parallel to a RF TV cable for about 10'. I know the output is clean and am wondering if this problem could be cause by anything more than just too long of a cable.

Years ago I hooked up my computer to my AVR and had the same problem. It's a ground loop as the computer was on a different circuit from the AVR. I used one of the below devices from Radio Shack, it solved the hum problem. There are probably more elegant solutions available including putting the computer on the same circuit, but the device below did the job. It's labeled as being for car audio but the principal is the same, they may even have one specifically for home audio.

http://www.radioshack.com/product/index.jsp?productId=2062214&cp=&origkw=ground+loop&kw=ground+loop&parentPage=search
RadioShack.com - Car: Accessories: Car A/V accessories: Ground Loop Isolator

was very helpfull thanks

I am having the same problem with humming that I can't figure out. I have a HK AVR 340 and I have run a 35' RCA cable from my mini-out on my computer to the reciever. The cable runs by one surge protector, my computer speakers subwoofer, and then parallel to a RF TV cable for about 10'. I know the output is clean and am wondering if this problem could be cause by anything more than just too long of a cable.

It can be. Since you need a very long cable to connect your computer to your receiver, I am going to guess that they may be on different electrical circuits. The ground potential of those circuits may be very different, even though the neutrals and grounds of both may be connected to the same bus bar in the breaker panel. This could definitely be a cause of your hum.

I had a similar problem when I ran a dedicated circuit for some components and used an existing one for another. There were many outlets, and lights on the one circuit, but only the AV components on the other. The problem disappeared when I connected everything to the same circuit, but this was too big of a load, so I ran an additional dedicated circuit. No problems.

If this is the case for you, you could verify it by temporarily using an extension to connect all the components (and computer) to the same circuit.

Just to add a note here on 12 V remote triggers. This was the problem on my setup. I have a B&K Ref 50 and the 12 V trigger to the B&K amp caused about half of the noise.

How did you fix the problem caused by 12V remote triggers? I have a power amp connecting to the pre-outs of a receiver. It worked fine until I use the 12V remote trigger.

How do I get rid of the hum in this case?
Yes, how did you?

When I originally called B&K with this question, they instructed me to sever the ground of the 12v connection (i.e. leave 'tip' connected, but sever 'sleeve'). This worked swimmingly.

However, another poster has raised a question about this solution (see post http://www.avsforum.com/avs-vb/showthread.php?p=8831624&&#post8831624 and following). I called back to B&K today to get a second opinion on this solution, and they confirmed its acceptability. Thoughts?

Years ago I hooked up my computer to my AVR and had the same problem. It's a ground loop as the computer was on a different circuit from the AVR. I used one of the below devices from Radio Shack, it solved the hum problem. There are probably more elegant solutions available including putting the computer on the same circuit, but the device below did the job. It's labeled as being for car audio but the principal is the same, they may even have one specifically for home audio.

http://www.radioshack.com/product/index.jsp?productId=2062214&cp=&origkw=ground+loop&kw=ground+loop&parentPage=search
RadioShack.com - Car: Accessories: Car A/V accessories: Ground Loop Isolator

Please explain how exactly this product would work as it appears to have two male ends at each end. How does it incorporate into the system? Do you need one for each component?

Please explain how exactly this product would work as it appears to have two male ends at each end. How does it incorporate into the system? Do you need one for each component?
No, just use it between the two. I'm trying to recall how I had it hooked up, I used a stereo phono mini-jack to dual RCA converter plugged into the PC. It looks like the thing on the left in the following link only it had female RCA jacks on the one side and stereo phono on the other side for the PC. They have them at RS.

http://www.radioshack.com/product/index.jsp?productId=2102695&cp=2032058.2032231.2032280&pg=2&allCount=341&fbn=Cable+type%2FAdapter&f=PAD%2FCable+Type%2FAdapter&fbc=1&parentPage=family
RadioShack.com - Cables, Parts & Connectors: Connectors & connectivity: A/V connectors & adapters: Gold Series 4-Piece Headphone Adapter Set

Just plug the RCA end into whatever input you want on your AVR, you may need to run a longer connecting cable. It worked okay, but nowadays many sound cards come with SPDIF outputs which can provide a much cleaner and probably better sounding connection, as long as the card handles Dolby Digital output.

I used one of those RS ground loop interruptors for a while, until I found out the spec's on them:

Ground LP Isolator (270-0054) Specifications Faxback Doc. # 9542

ELECTRICAL DATA:

Impedance Ratio:
Z1:Z2................................................1000 Ohms:600 Ohms
Z1:Z2................................................1000 Ohms:600 Ohms
Frequency Response:.............................300 Hz to 4000 Hz +/- 3 dB
DC Resistance:...............................................@2 5 degrees C
Z1:....................................................200 Ohms +/- 20%
Z2:....................................................150 Ohms +/- 20%
Insulation:.........................500 VDC apply to primary and secondary
more then 100 Meg Ohms Min.

(ALL-01/26/95)

I don't know what the performance is outside the 300-4000Hz. I was using it for my subwoofer, and I swapped it out for an ART DTI (which is good down to 10Hz.)

The RS solution is certainly not an ideal one if you want reasonably high quality analog playback, best to get a SPDIF Dolby Digital soundcard and go that route. There are probably other hum blockers that work better, the RS one was the first that came to mind.

I originally posted this in one of the projector forums, but it was suggested that I check here for help.

---------------

Trust me, I have searched a bunch on the forum, but can't find my answer.

All of my components (two Tivo's, DVD player, Yamaha receivers) are at the front of my room, and the projector (IN76) is at the back of my room. The outlets they are plugged into are on seperate circuit breakers.

The best I can tell, all equipment is properly grounded, including the Sattelite multiswitch outside and the sattelite dish on the roof.

I have a couple rolling bars slowly moving from the bottom of the screen to the top. If I put one of the 3 prong to 2 prong adapters on the IN76 power cord (eliminating the ground) the ground loop bars go away. So, it appears clear it is a ground loop.

The IN76 is plugged into a CyberPower UPS (550va), which I originally bought because we have frequent 1-3 second power outages during thunderstorms and I was trying to protect the projector/bulb. Obviously, this UPS is doing no line conditioning. I think this is the model (I bought it at Best BuY), but can't get to it easily right now to to confirm the model number. http://www.cyberpowersystems.com/CP550SL.asp

So, it appears that I need a line conditioner, or a UPS/Line Conditioner combo. I read in one thread that plugging a line conditioner into a UPS can be a fire hazard and void home owners insurance, but I don't know if that is true.

So, what is my best bet? It appears I need something with a floating ground setup (not even 100% sure what that means ), but I also need to keep my projector on a UPS because of the power outages.

I would rather not spend several hudred dollars if I can help it, so I would like the cheapest possible solution that will cover my ground loop issue and protect me from the thunderstorm power outages.

Thanks

Is there something else plugged into the same circuit the IN76? The best thing to do would be to get them on the same circuit somehow. Would running a sufficiently gauged extension cable back to the IN76 be too obtrusive? Have you considered having an electrician coming in and tying the circuits together? If you have any experience with wiring you could probably do it yourself.

My first guess would be that something else is plugged into the IN76 circuit, some dimmer style lights maybe, could even be in a different room. Try turning on everything in the house and then flipping the breaker the IN76 is on and see what else is on the circuit.

An extension cord wouldn't work as it is a front and back wall and no way to run an extension cord, except through the ceiling, and I am afraid that would be a no/no with fire code/home owners insurance. I will try turning everyhing on and flipping the breaker.

Would the electrician simply replace the two breakers (hooked to the outlets at the front and back of the room) with one larger one and tie those to legs together, or would he need to run a line from the front outlet to the back and tie only the one outlet that the IN76 is using into the same breaker as the front outlets.

Also, will a line/power conditioner fix this without the rewiring, or is this not the type of problem that a line conditioner fixes?

Regarding the line conditioning, I'm not an expert, but I doubt that would solve the problem unless you got the kind that had it's own power supply/transformer in it, and those I think are pretty expensive.

You could try running both circuits off of one breaker, one that is spec'ed for the load of course, and see what happens. That's something you could try yourself, be sure to throw the service disconnect though to make sure there is no power in the area of the panel you are working with.

Depending on the topography of the circuits in the room, it shouldn't be too hard a job for an electrician to create one circuit to tie all the equipment together.

You're going to spend money with an electrician, but I think the result will be better than spending money on power line conditions, etc. to try and solve the problem.

I am building a dedicated theater. The utility room is behind one of the side walls and the electrical panels are housed in the 2x6 wall. I am going to build a 2x4 wall for sound isolation from furnace units and water heater exhaust fans.

The question: Should I expect electrical interference problems from the electrical panels (I think they both bring in 600amp loads)?
If so, is there a way to shield against any potential problems?

Winkelmann

I have humming or buzzing coming from all my speakers that is quite loud. It only occurs upon start up of the system and each time works its way out after maybe four minutes. I have been researching this and have not heard of a similar situation, so I was wondering if anyone here might have an idea of what is going on. I do not think it could be a ground loop issue as I have everything going through a power conditioner. I just find it odd that the loud buzzing suddenly works its way out after only a few minutes and is only every present during power up. Any help would be really great.

My system consists of: Various B&W speakers, Denon AVR 3300, Bryston 4BSST, SA8300HD, Toshiba HD-A1, etc.

I have a puzzling one also, at least to me. I read this thread with interest as I do have a noise issue. I would call it a hiss and not a buzz or hum. In any case, I ran through the process on page one; I disconnected everything from the receiver (NAD T773) except for the speakers. No change. So apparently it's not a ground loop, which I suspected from the nature of the sound.

Ok, so what to do. No easy solutions apparent. But then I started playing around and found something interesting. After hooking the DVD player backup (Denon 3910) I realized that if the receiver is on any digital source from the DVD, optical or coax, I have the hiss. If I use the 5.1 analog inputs as the source....the his is almost non existent.

Anyone ever seen this or is there an explanation? Any and all input appreciated.

I have a Sony 5.1 receiver with Sony sub. The humming noise occurs when I connect a 1/8th to stereo phono plug from my computer to any of the RCA inputs on my receiver. The other plug that needs to be connected is the digital coax from my HD-DVR Cable box (Motorola brand from Comcast). When both are connected to the receiver, the hum occurs. I have switched to Optical for the time being from my cable box, and the hum is gone. However I would like to know what I could do to stop this hum from occuring when the coax is connected as I would prefer to use coax.

If the optical works I would just use that, but if you want to use the coax audio connection, try one of the DC blockers, or ground breakers like the ones found towards the bottom of the linked page below. You can find them at Radio Shack as well. It will need to be placed on the cable just before it feeds the cable TV STB.

http://www.hometech.com/video/atten.html
RF Attenuators, Filters, & DC Blockers - HomeTech Solutions

Theoretically, if the cable feed is grounded properly you shouldn't have the problem, but it's an extremely common problem, and the above devices should fix it.

Greetings,

Could someone who Knows compare/contrast the Xantech ground blocker referenced in that link to the, rather more expensive, Jensen Transformers VRD-1FF (http://www.jensentransformers.com/iso_vid.html)?

Thanks.

(Don't know if these have already been mentioned in this thread...)

A friend of mine had a hum that seemed to be pervasive in his system. No matter what he did, no matter which component was the source his front speakers always hummed. It was driving him nuts for weeks.

When I went over, I saw he had about 20' of speaker wire coiled up and tied together laying on top of all the other wires in and out of his receiver. We cut down his speaker wire to minimum length required and that did the trick. Even though all of his cables were shielded, the current running through the coils of speaker wire was apparently creating an inductor (or whatever the AC equivalent is) and interfering with the currents in his other wires.

Another source of hum can be the room itself. I've heard listening rooms where the studs in the wall resonate, and the sheets of drywall on either side act as drum skins. This is usually only noticable at higher volumes.

Test

(Don't know if these have already been mentioned in this thread...)

A friend of mine had a hum that seemed to be pervasive in his system. No matter what he did, no matter which component was the source his front speakers always hummed. It was driving him nuts for weeks.

When I went over, I saw he had about 20' of speaker wire coiled up and tied together laying on top of all the other wires in and out of his receiver. We cut down his speaker wire to minimum length required and that did the trick. Even though all of his cables were shielded, the current running through the coils of speaker wire was apparently creating an inductor (or whatever the AC equivalent is) and interfering with the currents in his other wires.

Another source of hum can be the room itself. I've heard listening rooms where the studs in the wall resonate, and the sheets of drywall on either side act as drum skins. This is usually only noticable at higher volumes.

Interesting. Any chance have you had experiences with more of a "hiss" or a "crack/pop" from speakers? I auditioned a pre/pro recently and you could hear a hiss from about 4' away (my ref receiver was dead silent). Also, (perhaps not related), as I passed DirectTV through it, it would "crack/pop" every time I changed channels. I returned it to the owner and the problems went away.

Unfortunately for me, most of this thread is above my head, but I have what I think is an easy hum question...

7.1 setup, Denon 2807, 2 amps (for front & surround), Yamaha DVD. My hum obviously is associated with CATV, because when I unhook the cable for music listening, no more hum.

I believe there are enough plugs on my power conditioner (or whatever it's called) for everything, though I may have the sub plugged separately into same wall outlet. There are also CATV in/outs on the conditioner I recall (I'm not home at the moment).

Can I plug the CATV into the conditioner, and then from there into the TV? Will that do the trick, or am I way off base?

Thanks!

Unfortunately for me, most of this thread is above my head, but I have what I think is an easy hum question...

7.1 setup, Denon 2807, 2 amps (for front & surround), Yamaha DVD. My hum obviously is associated with CATV, because when I unhook the cable for music listening, no more hum.

I believe there are enough plugs on my power conditioner (or whatever it's called) for everything, though I may have the sub plugged separately into same wall outlet. There are also CATV in/outs on the conditioner I recall (I'm not home at the moment).

Can I plug the CATV into the conditioner, and then from there into the TV? Will that do the trick, or am I way off base?

Thanks!

Some power conditioners have surge suppressors for cable (could be antenna, dish, or cable TV). But those do nothing to stop hum. Very few power conditioners include a cable surge suppressor that also "breaks" (interrupts) the ground/shield (the Furman 20i does have isolated ground AND surge suppression, other models of theirs may have the same feature, and other brands might have it too, but if they don't SAY it isolates the ground, it doesn't.

So let's assume you don't have one of the power conditioners that DOES isolate the cable ground... what should you do? There's a company called Jensen Transformers who makes an EXCELLENT quality ground loop breaker. You need a second piece of cable to use it. You plug 1 end of the existing cable into the isolator, then plug the new length of cable into the other end of the isolator and then to wherever you need it to be connected. Now the ground for the cable (the shield) is 'broken' and you have isolated the cable ground from the ground from the rest of your system.

Why does the system hum when you connect the cable now? The place the cable is grounded is different than the place your house wiring is grounded. The cable may be grounded to a bar driven into the ground somewhere outside of your house or possibly to a water pipe inside your house somewhere. If the cable installer had run a ground wire from the cable where it comes into your house to the ground rod for your home's entire electrical system, chances are, that would also stop your hum.

When grounds exist in 2 different physical locations, you end up with a real electrical current flowing between those 2 grounds and THAT current flow produces the hum you hear.

If you have Cable TV (not satellite) you want Jensen's Iso-Max VRD-1FF... $60 MSRP. It doesn't appear that they have a product that will work with a satellite feed which can have the same problem. In that case, trying to relocate the ground for the satellite feed to the home's electrical system ground could stop the problem too. Or perhaps some other company that makes these sort of devices has one that works with satellite systems.

When you have this sort of ground loop (different physical ground locations), you may notice that when the ground is wet, the hum is not quite as bad as when the ground is really dry! The moisture affects the conductivity of the earth/ground and that changes the amount of hum you hear in the system.

You probably CAN'T fix the hum by running a wire between 2 different ground rods. You have to physically disconnect from one ground rod (or water pipe) and ground everything to the home's ground rod (often a crow-bar looking thing sticking out of the basement or slab floor or out of the foundation somewhere, or beside the home somewhere not too far from the electrical panel (ours goes through the slab in the garage and the electrical panel is not far from the ground rod). Some fairly beefy wires will be clamped to that ground rod. You can clamp another wire to that rod (don't disturb the existing ground, get a new clamp and add it to the rod, Lowes and Home Depot have them in the electrical department) and run that wire to where the cable or satellite ground had been located before (sometimes to a splitter or a fitting in the cable with a ground screw and hole coming off one side with a bare wire held into the hole by the screw).

Ground loops are fun! Especially when you fix one!

I have a hum problem on my TV speaker audio. The audio source is the analog audio output from a STB via RCA cables. My HD STB has an digital audio output, but the TV doesn't have a digital audio input. Are there HD TV's that do have digital audio inputs?

I have a hum problem on my TV speaker audio. The audio source is the analog audio output from a STB via RCA cables. My HD STB has an digital audio output, but the TV doesn't have a digital audio input. Are there HD TV's that do have digital audio inputs?
Try using a DC-blocker on the cable feed to the STB like the one's listed in the linked page in post No. 64 above.

Anyone know of any Ground Breakers for use with Digital Cable? (all the ones I've found are not compatible with digital cable)

Anyone know of any Ground Breakers for use with Digital Cable? (all the ones I've found are not compatible with digital cable)

http://jensentransformers.com/

You want the VRD-1FF $59.95 - compatible with analog and digital cable.

Not compatible with satellite installations.

Thanks for the link!

I have a low hum that can only be heard with my ear up to the device. It is coming from a Onkyo 390 CD changer when it is off.

Is this normal or just floor noise from the player?

thanks...

I have a strange ground loop. I did what was recommended and disconnected everything from my prepro. The hum occurs when I put my Scientific Atlanta 4250HD cable box back in the circuit, but does not go away when I disconnect the cable input to the box. But if I disconnect the HDMI cable from the cable box to the prepro, or pull out the electrical cord from the cable box, the hum goes away. The hum is only heard when I use the Tv input on the prepro, not if I am watching a DVD or anything else. I tried bringing the cable box back to Cablevision, but a replacment cable box has the same problem. The box has a 2 prong plug, so I assume a ground lifting plug won't work.

I thought if the ground loop is coming from your cable, it would go away if you disconnect the cable feed from the cable box?

Any suggestions?

I have a strange ground loop. I did what was recommended and disconnected everything from my prepro. The hum occurs when I put my Scientific Atlanta 4250HD cable box back in the circuit, but does not go away when I disconnect the cable input to the box. But if I disconnect the HDMI cable from the cable box to the prepro, or pull out the electrical cord from the cable box, the hum goes away. The hum is only heard when I use the Tv input on the prepro, not if I am watching a DVD or anything else. I tried bringing the cable box back to Cablevision, but a replacment cable box has the same problem. The box has a 2 prong plug, so I assume a ground lifting plug won't work.

I thought if the ground loop is coming from your cable, it would go away if you disconnect the cable feed from the cable box?

Any suggestions?

It's POSSIBLE the box would be quiet with a good ground from the cable - or not. Hard to know for sure.

Does your prepro have an AC convenience outlet on the back? If so, try plugging the cable box into that and see if the hum is still present. If it is not, you can either leave the box plugged in there, or you can plug the cable box into the same AC outlet as the prepro. Be sure when you connect the cable box to the prepro, the CABLE is not connected but do connect the HDMI cable to the monitor. You want to know if the box/monitor/prepro can be hum-free before introducing the cable. If you are hum-free without the CABLE and hum starts when you connect the cable, you'll need a cable isolator to break the ground loop.

Ground lifting plugs are dangerous and should be illegal - they can lead to electrocution if the product they are used with has a fault that allows AC to reach the chassis. Nobody should ever use a ground lifting plug unless you have a meter and can verify that the chassis is not floating at some potential that could electrocute you under the right conditions. But you said it was a 2-wire plug anyway - the ground is the 3rd wire so no-3rd wire, no ground is there to lift anyway. Products like that have to be manufactured a specific way to keep them from becoming an electrical shock hazard.

so I disconnected the cable wire from the cable box and turned it on, the hum is still there. But it goes away if I disconnect either the HDMI cable or the electrical plug from the cable box. There are no extra outlets on the back of my prepro, but I have it plugged into the same outlet. The HDMI cable is the better Blue Jeans cable, which should be pretty heavily shielded, so I don't think that's the issue. I tried plugging the HDMI cable into a different input on the back of the prepro, so I don't think it's a broken HDMI input on the prepro either.

1) Have I ruled out cable ground as being the source of the problem?
2) Any other suggestions?

so I disconnected the cable wire from the cable box and turned it on, the hum is still there. But it goes away if I disconnect either the HDMI cable or the electrical plug from the cable box. There are no extra outlets on the back of my prepro, but I have it plugged into the same outlet. The HDMI cable is the better Blue Jeans cable, which should be pretty heavily shielded, so I don't think that's the issue. I tried plugging the HDMI cable into a different input on the back of the prepro, so I don't think it's a broken HDMI input on the prepro either.

1) Have I ruled out cable ground as being the source of the problem?
2) Any other suggestions?

Is the cable ruled out? Maybe, maybe not. It all depends on where else the cable goes. If it goes to a cable modem and you have an ethernet connection to a PC that's connected to the system somewhere - or an ethernet cable connected to a disc player that's connected to the pre-pro - the cable could still be implicated in a system hum problem. If the cable doesn't connect directly or indirectly to the system anywhere else, it sounds like you need an isolated HDMI interface - and I'm not sure if that's even possible, let alone available.

Try disconnecting all other components from the pre-pro and repeat your experiment with the cable box and hdmi cable to see if there's a hum issue without all the other components connected. If the hum is gone, you can connect other components 1-at-a-time to see if there's 1 component that brings the hum back. When you know what component that is, you can check where the connections come from and where that component is plugged in - moving the plug may help. Isolating the connections to the component may help.

I've read this thread and can't find the exact answer I'm looking for. I'll start with some set-up info and then explain my problem.

I'm using a Pioneer Vsx-80tx receiver. All of my speakers wires are routed through the walls and terminate at a speaker panel behind the receiver. I have a Klipsch RW-10d sub. The sub is digital, so I run pre-amp level signal wires (right and left) to the sub. This was set up and running for almost a year. Recently, I noticed a loud hum coming from the sub only. Here's the wierd part. When the receiver is on, I can't really hear anything, and when you turn it off, there is no hum. BUT, in about 90 seconds, the sub starts humming loud enough that I can hear it anywhere in the house. If I unplug the receiver (power cord) and plug it back in, the hum stops and then picks up in 90 seconds again. So, being an engineer, I assumed ground loop. I went through all the trouble shooting (unplug this and that) and determined that if I unplugg the phono plugs from the back of the sub, the hum stops. Plug them in and unplug the phono jacks from the receiver and the hum is literally deafening! So the problem is somewhere in the signal wires to the sub. I took a length of wire and attached it to the shield of the signal wires and then grounded it, and presto! Hum is gone. Even with everything plugged back together and the receiver turned off.

So my question is two parts. First, why did this suddenly start humming when the system is unchanged in anyway? Second, am I asking for trouble by grounding the signal shield to earth seperately from the internal grounding that should occur in the receiver or sub amp? I don't want to burn out my receiver.

I've read this thread and can't find the exact answer I'm looking for. I'll start with some set-up info and then explain my problem.

I'm using a Pioneer Vsx-80tx receiver. All of my speakers wires are routed through the walls and terminate at a speaker panel behind the receiver. I have a Klipsch RW-10d sub. The sub is digital, so I run pre-amp level signal wires (right and left) to the sub. This was set up and running for almost a year. Recently, I noticed a loud hum coming from the sub only. Here's the wierd part. When the receiver is on, I can't really hear anything, and when you turn it off, there is no hum. BUT, in about 90 seconds, the sub starts humming loud enough that I can hear it anywhere in the house. If I unplug the receiver (power cord) and plug it back in, the hum stops and then picks up in 90 seconds again. So, being an engineer, I assumed ground loop. I went through all the trouble shooting (unplug this and that) and determined that if I unplugg the phono plugs from the back of the sub, the hum stops. Plug them in and unplug the phono jacks from the receiver and the hum is literally deafening! So the problem is somewhere in the signal wires to the sub. I took a length of wire and attached it to the shield of the signal wires and then grounded it, and presto! Hum is gone. Even with everything plugged back together and the receiver turned off.

So my question is two parts. First, why did this suddenly start humming when the system is unchanged in anyway? Second, am I asking for trouble by grounding the signal shield to earth seperately from the internal grounding that should occur in the receiver or sub amp? I don't want to burn out my receiver.

I don't know why it would start now if it hadn't always been there. I have exactly the same issue in my system from time to time - configuration changes frequently though, so it comes and goes. But one AVR or another is always present when the problem happens and it's always the subwoofer connected to the LFE output on the receiver that hums. My sub has a ground post on the amplifier module. I connected a 16 gauge stranded copper wire from the ground post on the subwoofer to the ground post on the recever (normally would be used for a record player, you remember those? LPs? 45s? vinyl?) and that stopped 60% of my hum problem. The remainder of the hum problem was stopped by running a 10 gauge power-tool extension cord from the same power conditioner the receiver is plugged into all the way to the back of the room where the LFE subwoofer is located. That stopped the remaining 40% of the hum when the receiver was turned off.

Hope this helps!

PS - If you have no ground post on the subwoofer amp module, scrape some paint from around one of the mounting screws and put the ground wire under that mounting screw (assuming you have a metal plate on the back of the subwoofer).

I don't know what they heck they have done to these receivers to make the hum start like that when you turn off the receiver - it is really odd. Almost like they put a voltage on the shield/return of the line level outputs.

I have the problem with my cable tv not being properly grounded. When I disconnect the coax cable from the box, the hum goes away. I have digital cable, would one of those RF attenuators from Radioshack work just as well as one of those jensen transformers?

I have the problem with my cable tv not being properly grounded. When I disconnect the coax cable from the box, the hum goes away. I have digital cable, would one of those RF attenuators from Radioshack work just as well as one of those jensen transformers?

No, you have to isolate the ground - that's the whole point of an isolation device and it also accounts for why they are expensive compared to a simple attenuator that just reduces signal strength and nothing else. A resistor in a housing is all an attenuator is. An isolator has to have transformers that allow the signal to "jump" across from one side of the transformer to the other without having a physical connection.

Ok. Well how about those monster cable surge protectors? I know that they have hook ups for coax. Would one of those work? I ask, because I need a surge protector and that I way I don't have to pay for the transformer only and I'll get more use out of the surge protector.

Ok. Well how about those monster cable surge protectors? I know that they have hook ups for coax. Would one of those work? I ask, because I need a surge protector and that I way I don't have to pay for the transformer only and I'll get more use out of the surge protector.

Monster's coax connections don't isolate the ground on the cable connectors. They and everybody else I've checked so far don't go to the expense of isolating the cable ground... with 1 exception. Some Furman products with cable connections DO isolate the cable ground... the $3000 20i does, for example. Not sure how far down their product line you can go and still get the isolated cable ground though.

I have a ground loop issue between my computer and the receiver. Since the computer and receiver are on the same electrical circuit but different outlets, I end up with a group loop issue. The audio between the computer and receiver are connected via stranded copper wire with mini RCA 3.5mm and RCA jack ends. Though they both share the same ground wire, they're at different outlets which according to this thread creates two different ground potentials and therefore a ground loop. So I'm wondering, how can I alleviate this issue? This problem is different from the cable since all you have to do is use the same ground as the house wiring. Also how come my reciever doesn't have a 3 prog electrical plug? How exactly is it grounded?

Also btw, I was wondering if this was normal but when I turn up the volume to the max, along with the hum, I can actually hear the audio from another input that isn't selected.

I have a ground loop issue between my computer and the receiver. Since the computer and receiver are on the same electrical circuit but different outlets, I end up with a group loop issue. The audio between the computer and receiver are connected via stranded copper wire with mini RCA 3.5mm and RCA jack ends. Though they both share the same ground wire, they're at different outlets which according to this thread creates two different ground potentials and therefore a ground loop. So I'm wondering, how can I alleviate this issue? This problem is different from the cable since all you have to do is use the same ground as the house wiring. Also how come my reciever doesn't have a 3 prog electrical plug? How exactly is it grounded?

Also btw, I was wondering if this was normal but when I turn up the volume to the max, along with the hum, I can actually hear the audio from another input that isn't selected.

You're problem would most likely be fixable with a stereo audio isolator inserted between the computer and receiver so there is no direct electrical connection between the receiver and computer -- the audio signal gets through across an isolation transformer.

However, if the computer is generating audio hum rather than an actual ground loop hum... that won't be stopped since that would be part of the signal. If you connect GOOD headphones to the computer... headphones that can produce actual bass frequencies below 50Hz, and you hear hum in the headphones, the computer is creating that and it's not a ground loop. If there's no hum in the headphones, you probably do have a ground loop. Do the headphone test with the computer disconnected from the receiver.

www.jensentransformers.com (http://www.jensentransformers.com) sells an excellent quality stereo audio isolator. There may be other sources with lower prices and lower audio quality. the quality of the transformers in these isolators has a pretty significant effect on audio quality. It won't bother compressed MP3 much, but if you are trying to play uncompressed sources and want good sound, the Jensen product is the way to go.

I'm getting a strange hum issue: my Kef 5005 (old model) powered sub hums only when my AV receiver (Onkyo 705) is off. When I turn the Onkyo on the hum goes away. Any pointers or is this a hum issue I shouldn't be worried about?

I'm getting a strange hum issue: my Kef 5005 (old model) powered sub hums only when my AV receiver (Onkyo 705) is off. When I turn the Onkyo on the hum goes away. Any pointers or is this a hum issue I shouldn't be worried about?

Something odd happens in many AVRs or processors with 2-wire power cords. I have the same thing happen with Onkyo and Pioneer AVRs of recent vintage and I suspect other brands are doing the same thing, whatever it is. If your sub has an external ground post, you can try running an extra ground wire from the sub to the AVR chassis, but that's not likely to solve the problem - those ground wires tend to be more effective when the AVR is powered-up.

If the AVR and sub aren't connected to the same power outlet or power conditioner, you could try an extension cord on the sub to see if it stops humming when plugged in to the same place the AVR is plugged in. But I wouldn't run out and get a big fancy extension cord right away, because this may not help either, try it with any old cord you have around the house first to see if that does any good. It should be a 3-wire cord if your sub has a 3-prong AC plug.

im having a hum problem to.......i tried unpluging the 705,my tv, and my ps3 but the hum was still there,(says to try these things in the faq) i had my sub pluged in a surge protecter outlet that i got from bestbuy along with the tv and ps3, took it out from there and pluged it directly inside the wall socket but the hum is still there. and my hum turns on for awile and off awile. and i dont know if this happend because of the sub but last night the section where i have all my stuff hooked had a power outage. everything just cut off wile i was playing a game. everthing else in my room was still on except for that section.
everthing is back on now but from now on i just unpluge the sub when im not using it(its ok to leave it unpluged right?)
and by the way i dont have the 3 socket pluge i have the two.

and on my surgeprocter box both lights that say ground and surge are on what does that mean?.

Just a quick thanks for this sticky. Two days ago I got a Vizio LCD and an Onkyo SR605 to go with my Time Warner Samsung HD box. Well, I can't figure out a solution to the HDCP problem that's keeping me from running the cable HDMI through the Onkyo, but I can run it into the TV and run digital audio (coax) into the Onkyo. The Onkyo has an HDMI running into the TV also, for the DVD and other stuff.

So, that three-way dance caused a hum. After getting down to the bare minimum config and still having the hum, I called Onkyo and spent 40 minutes resetting everything and undoing all the speaker wires, and finally having the guy tell me to exchange it where I bought it. Hey, that thing weights 20 pounds easy and is one PITA to return. Plus, I really didn't think it was bad.

Then I looked here and read the sticky. Oh. Well, I still don't really know what the problem is, though I see lots of things to try, like post 64. Still, the critical thing for me so far was reading that optical doesn't cause this problem. I switched the box > onkyo from coax to optical and there went the problem. Happy happy joy joy. I'll look into the other stuff, but at least I can sleep tonight without cursing.

^ I second the thanks. I've just gone from clueless to somewhat informed by reading this and similar threads. The trigger? I just hooked up my new Onkyo 705 last weekend and entered the anoying world of ground loop hum. In my case, I think the problem is pretty clear. My Comcast cable is apparently at odds (ground wise) with the grounding prong in my PJ's 3-pronger. If I disconnect the cable from the cable box; dead silence. If I unplug the projector; also dead silence. Both hooked up (the two ends of the ground loop) and it hums away.

A side effect of these great new switching receivers, is that they are now in the middle of all connections, meaning any ground loop will pass through them and bring the hum. Prior to this, my old AVR was sitting on the side getting digital audio via coax for the cable box and optical for the HD-DVD. No opportunity in that setup for the cable ground vs. projector ground to show up in the AVR. I've got Comcast coming out to work on a better gound at the service entrance, but won't hesitate to buy the Jensen Isolator if need be. Like the last guy, I'm just glad I don't have to mess with returning the AVR, only to find that I still have the problem. :)

^ I second the thanks. I've just gone from clueless to somewhat informed by reading this and similar threads. The trigger? I just hooked up my new Onkyo 705 last weekend and entered the anoying world of ground loop hum. In my case, I think the problem is pretty clear. My Comcast cable is apparently at odds (ground wise) with the grounding prong in my PJ's 3-pronger. If I disconnect the cable from the cable box; dead silence. If I unplug the projector; also dead silence. Both hooked up (the two ends of the ground loop) and it hums away.

A side effect of these great new switching receivers, is that they are now in the middle of all connections, meaning any ground loop will pass through them and bring the hum. Prior to this, my old AVR was sitting on the side getting digital audio via coax for the cable box and optical for the HD-DVD. No opportunity in that setup for the cable ground vs. projector ground to show up in the AVR. I've got Comcast coming out to work on a better gound at the service entrance, but won't hesitate to buy the Jensen Isolator if need be. Like the last guy, I'm just glad I don't have to mess with returning the AVR, only to find that I still have the problem. :)

The only things that will stop the ground loops are if the cable is grounded to the grounding rod for the whole house or using a device like the Jensen Transformers cable isolator. The ground rod might be in the garage, or somewhere outside the house, probably close to the electric meter, or it may be in the basement near the location where the power feeds into the house from the meter. If the house is older, it may be relying on metal plumbing pipes for the ground which is NOT a good idea. The older the house is, the stranger and more oddly located the ground rod may be - or as noted, there may be no ground rod at all. The ground rod often looks similar to a piece of rebar (reinforcing bar used in cement) with a clamp on it and some electrical wiring being clamped to the bar. This bar may be protruding from concrete in the garage or basement, or it may be burried in the earth beside the home with the top sticking out of the ground. Protected locations (garage or basement) are preferred to minimize weathering effects on the electrical connections.

The ground rod might be in the garage, or somewhere outside the house, probably close to the electric meter, or it may be in the basement near the location where the power feeds into the house from the meter. If the house is older, it may be relying on metal plumbing pipes for the ground which is NOT a good idea.

While all that is true (and useful :) ) for someone living back East, here in Arizona it's a different game. IIRC, the grounding rods for the houses in my neighborhood are buried beneath the slabs where there is at least a chance of some moisture in the ground. The service panel has nothing going into the ground other than the large conduit bringing in the underground electrical main. Plumbing is non-metallic. Of course, Comcast just slapped a metal clamp around the counduit and attached the ground wire from the cable box to it. I doubt the conduit extends into the soil more than a foot, and it is probably a poor electrical connection with the panel and the neutral/ground connections within. I'm giving Comcast a chance, since they charge so many $$$$ for everything. Worst case, I'll waste a half hour of my day off. Best case, they'll either improve the ground enough to eliminate the ground loop or supply an equivalent to the Jenson transformer. We'll see.....

While all that is true (and useful :) ) for someone living back East, here in Arizona it's a different game. IIRC, the grounding rods for the houses in my neighborhood are buried beneath the slabs where there is at least a chance of some moisture in the ground.

Well, I'm not in the East, I'm in Colorado with very little rain or snow. And it's no different in AZ because garages are slabs, so are basements. When there's no basement the ground rod installation is the same as it would be if the rod was in the garage or basement... drive the rod several feet into the ground (how deep is established by state electrical code), compact the earth, lay a vapor barrier, install the rock layer, pour the cement.

Back east, most of the time the rods are inside the house (garage or basement), but I have seen them outside near the meter, probably the only variation you won't see in dry climates.

Well, I'm not in the East, I'm in Colorado with very little rain or snow. And it's no different in AZ because garages are slabs, so are basements. When there's no basement the ground rod installation is the same as it would be if the rod was in the garage or basement... drive the rod several feet into the ground (how deep is established by state electrical code), compact the earth, lay a vapor barrier, install the rock layer, pour the cement.



Sounds like I would be better off in Colorado.....

But seriously, I watched every step of my house being built and have lived in it for twelve years. There is no exposed ground rod anywhere. I vaguely remember them having routed the heavy copper cable inside the 8" wide stem wall that the service panel sits over. I have a raft foundation, so things may be different than the normal footer/slab or post-tension foundations.

I'm giving Comcast a chance, since they charge so many $$$$ for everything. Worst case, I'll waste a half hour of my day off.

I was right! I DID waste a half hour of my day off. Two techs were here and when I mentioned ground loop, they looked at each other with that revealing blank look. Then, I added to my wasted time by explaining that the ground of their incoming cable was at a slightly different potential than the ground of the single three-pronged device in the system (my PJ). I then demonstrated that if I unhooked the cable, the hum stopped; if I unplugged the PJ, the hum stopped. With both connected, the hum was very noticeable.

At that point, the more seasoned of the two pulled out his multimeter, checked the outlet my PJ was plugged into and proceeded to proclaim that the reason for my hum was that the outlet measured at 123 volts. :rolleyes:

Needless to say, I wasted NO time in ordering one of the Jensen Isolators before they were even out of the neighborhood.

Cable company weasels - it's a wonder the "expert" knew how to measure the outlet voltage without electrocuting himself. To say these guys are "technicians" is like saying I'm a web page designer by adding my post to this thread.

You've got that right. I concluded that any time a Comcast tech decides that they have a customer with an "imagined" problem, they're advised to pull out the fancy meter and make some goofy recommendation designed to get the OCD customer's energy focused in some other direction. These guys didn't even do a convincing job at that.....

Hey all - First post.

I had the audio hum problem (ground loop) problem caused by coaxial cable. Both lines were previously grounded outside the house, but that didn't help with the hum. I had the same problem with my system with two different TV's. My original solution was to use one of those ground-breaking filters, but that degraded my picture quality to an unsatisfactory level.

I recently bought a new TV and it had a two coaxial hookups, one for cable/satellite and the other for an antenna. Those filters are quite expensive and as I said, they degraded the picture. I scratched my head for quite a while, but finally found a solution that worked well.

I bought a coaxial ground breaker and grounded it to my surge suppressor. Pretty simple and it completely eliminated the hum and there's no picture loss.

Here are the two pieces of equipment I used.

Paladin Tools - Dual port ground block

Panamax - Max 4400 20A surge suppressor.

(couldn't post links because of newbie status)

Many surge suppressors have grounding lugs and I would assume most people have invested in one. The ground breaker is only $3.50 and it works up to 3Ghz. I made two 1 ft. coaxial cables from the ground break to the TV and used a solid grounding wire.

In addition to the setup, I added a splitter for the OTA connection and used the second run for FM stereo. Sounds great and no degradation of video or audio. FYI my antenna amplifier is before the ground.

Perhaps this is a cheaper and easy solution for those not wanting to invest in those expensive filters.

Cheers!

Peter

Needless to say, I wasted NO time in ordering one of the Jensen Isolators before they were even out of the neighborhood.

Update: the Jensen Isolator is now installed. The thing works as advertised and I feel safe in strongly recommending it to everyone. There is no longer any trace of hum in my system, regardless of source. :) :)

I just got an Onkyo 705 and have a severe hum problem, audible in the main speakers as well as the sub.

I have no cable or satellite box and disconnecting the cable from the FM antenna didn't help.

I shorted the outer shell of the 705's HDMI output connector to the 705 chassis ground screw; didn't help.

As soon as I disconnect the 35' HDMI cable that runs to my projector, it goes away.

All devices with 3-prong plugs are properly grounded, eventually, to ground rods at the main service entrance and subpanel.

Any suggestions?

I just got an Onkyo 705 and have a severe hum problem, audible in the main speakers as well as the sub.

I have no cable or satellite box and disconnecting the cable from the FM antenna didn't help.

I shorted the outer shell of the 705's HDMI output connector to the 705 chassis ground screw; didn't help.

As soon as I disconnect the 35' HDMI cable that runs to my projector, it goes away.

All devices with 3-prong plugs are properly grounded, eventually, to ground rods at the main service entrance and subpanel.

Any suggestions?


Do you have any light dimmers on the same circuit? Does your HDMI cable run along any AC house wiring and/or power cords?

"Do you have any light dimmers on the same circuit? Does your HDMI cable run along any AC house wiring and/or power cords?"

No to both.

Thanks.

35' That's a long cable run. Have your tried moving the projector close to the receiver and using a shorter HDMI cable to see if the noise is still there? Might be a big hassle if you already have it mounted.

Sure would be; it's behind the back wall.

I'll try a cheater plug on the pj and see what happens.

The cheater plug on the pj got rid of the hum, so I ordered a Hum X. Hope it works.

I have a 10' SVS box sub, which I love. I changed receivers a few days ago, and since then have been having a bad hum whenever the new receiver is off. When I tried to trouble shoot this I discovered a few things, all of which make me confused:

1) The BASH amp in the sub doesn't have a grounded power plug, so, even though I bought a cheater plug to test, there's no ground to lift. Everything I've read says that an ungrounded sub should only be a temporary condition, but this doesn't even have the option. Why?

2) I bought a cheap isolator from Radio Shack today to test that, but in the course of testing it discovered that if I plug it into the line in on the Sub and then touch either the post or ring of the matching RCA jack I get a hum, like my finger has enough current to drive the amp, the volume of the hum does respond to the gain control. This effect is independent of the Isolator, I tested it with a regular cable. I assume it's related to my finger creating a ground condition with my feet and the house and that's what I'm hearing.

3) What's happening here, and is there anyway to fix it?

Sure would be; it's behind the back wall.

I'll try a cheater plug on the pj and see what happens.

NO CHEATER PLUGS... EVER! PLEASE! People have been killed by products plugged in with cheater plugs. DON'T DO IT!

There's a 99.9% chance your hum will disappear if you get a decent 35' AC extension cord (get one for power tools like saws or compressors) and plug it in to the same outlet or power conditioner as the AVR.

You have a ground loop that's being caused by the projector ground and AVR ground not being at the same potential. The cheater plug will probably stop the hum - but you will be putting yourself in danger. You can try the cheater plug briefly to see if the hum goes away... if it does (and it probably will), remove the cheater plug right away, then get the nice grounded extension cord and use that to power the projector instead of the outlet it's plugged into now.

I’ve made a few changes to the surround channel arrays or the amplifiers that they drive, which has now induced the elusive mains humming sound transmitted though one of many electrical items.

So far I’ve isolated but one amplifier Marantz 1050 that runs the centre HF and centre back surrounds.

Now here is the funny the humming that is being produced on the sidewall surrounds driven by the Marantz 1030 only occurs when I turn on the second Marantz 1050, I have two of them. Now if I turn on the other Marantz 1050 the hum is induced over to the Marantz 1030, weird but true. Now if I undo the RCA phone leads leading to the Marantz 1030 the hum goes away, but that’s not going to help because I need to here the sidewall surrounds, don’t I.

I’ve checked the earth leads connected to them and even undone one or two to see if that clears it, as its worked in the past.

I’ve even tried attaching some wire to the (outside chassis casing) and attached the wire to several electrical items to see if that clears it. So far this has been a fighting challenge to solve the (elusive humming) does something give here for Pete shakes!

Anyways I don’t like giving up and I’ll keep go at it, until I track down the curse of the (elusive mains humming gremlin).

Oh, last time it took me 24 hours around the clock to find main hum that was induced by the new, well old, but it was new to me, TV and all I had to do was undone a sodden earth lead on an active crossover network.

In response to myself:

I fixed the problem by replacing the subcable, which used to be a very poorly insulated RCA run with a length of R6 Coax terminated in RCA connectors. It works great now, but I left the isolator off the linkage since it was inducing hum itself (the leads on the Rat Shack Isolator are very thin and poorly shielded too). I don't know if that means that there's some major interference source in the room or what, but since the problem is gone I've stopped caring.

maxdb,

"NO CHEATER PLUGS... EVER! PLEASE! People have been killed by products plugged in with cheater plugs. DON'T DO IT!"

Just for a couple of days, I promise.

I don't see the danger, as the pj has a plastic case.

"There's a 99.9% chance your hum will disappear if you get a decent 35' AC extension cord (get one for power tools like saws or compressors) and plug it in to the same outlet or power conditioner as the AVR.

You have a ground loop that's being caused by the projector ground and AVR ground not being at the same potential. "

All of the ground wires are connected together via the electrical system, it's just a question of the length/resistance of each conductor.

What's to keep the ground wire in the long extension cord from also causing hum?

In any case, because I have no attic and am on a slab, the only way to do that is another conduit run on the roof; not gonna happen.

maxdb,

"NO CHEATER PLUGS... EVER! PLEASE! People have been killed by products plugged in with cheater plugs. DON'T DO IT!"

Just for a couple of days, I promise.

I don't see the danger, as the pj has a plastic case.

"There's a 99.9% chance your hum will disappear if you get a decent 35' AC extension cord (get one for power tools like saws or compressors) and plug it in to the same outlet or power conditioner as the AVR.

You have a ground loop that's being caused by the projector ground and AVR ground not being at the same potential. "

All of the ground wires are connected together via the electrical system, it's just a question of the length/resistance of each conductor.

What's to keep the ground wire in the long extension cord from also causing hum?

In any case, because I have no attic and am on a slab, the only way to do that is another conduit run on the roof; not gonna happen.

As long as the long extension cord has a large enough wire gauge to read very close to 0 ohms from end to end, it will not induce a loop. The whole point of plugging it into the same outlet or power conditioner as the AVR/processor is to put the projector ground and AVR/processor ground at the same potential - which they will be if the extension cord is a good one (for use with saws and other high-current tools). I wasn't advocating installing it in the wall, floor, or ceiling. I was thinking you'd just run it around the perimeter of the room... from where the AVR/processor is plugged in to where it needs to be to plug in the projector.

Certainly the bottom of the projector has exposed metal? Any exposed metal part on the projector can be at 120VAC if you use a cheater plug... touch the wrong spot and your heart can be stopped. It doesn't happen often... but it does happen. Connectors usually have metal around them...those could be raised to 120VAC when using a cheater plug also. There has to be a component failure in the "cheated" product for this to happen - but it can happen.

HELPP!!!!!!!

I've got a VERY LOUD ground hum that just started after someone decided it would save alot of time to install a fan light fixture without cutting the power to the line before working. After alot of sparks I developed a very loud ground hum. It is present on alot of outlets in that area of the house I plug the sub into. If i run an extension cord to some different outlets in the room or other places in the house it isn't evident at all.

I've tried removing the switch that got zapped and still have the humm. I tried a plug with the ground pole removed(cheater plug?) and its still there and still loud.

Can this be a problem at the individual breaker? How can I find the source.

Sounds like the fan is not wired properly or that you're pulling too much juice from the circuit.

HELPP!!!!!!!

I've got a VERY LOUD ground hum that just started after someone decided it would save alot of time to install a fan light fixture without cutting the power to the line before working. After alot of sparks I developed a very loud ground hum. It is present on alot of outlets in that area of the house I plug the sub into. If i run an extension cord to some different outlets in the room or other places in the house it isn't evident at all.

I've tried removing the switch that got zapped and still have the humm. I tried a plug with the ground pole removed(cheater plug?) and its still there and still loud.

Can this be a problem at the individual breaker? How can I find the source.

You are in very dangerous territory right now. It does not sound like you have the knowledge or skill with electrical wiring and electricity to safely diagnose what is going on. Doing the wrong thing, like using a cheater plug which you already tried, can put your life at risk. This is something for a knowledgeable professional - and I don't mean Joe Electrician who runs wires and hooks up outlets or fans. Something is fundamentally messing with your wiring and until it is fixed, I would not even operate my system on that power.

It might be something completely safe, but troublesome, but it could also be something that could burn your house down or damage your equipment. I would not take chances.

GROUND-LOOPING PROBLEM

I have read a lot of forums on this, but for me, all the solutions given have not worked for me. I keep getting oud buzzing noise in my right speakers. Here is my scenario. I have a Macintosh Powerbook.

The audio out of the laptop goes into an M-Audio MobilePre (Audio Interface)

From there, White/Red RCA output cables WITH a ground-loop isolator connect to my Onkyo receiver.

From there the Onkyo receiver connects to 2-sets of speakers. Speaker set A and B.

Both my laptop and receiver have 2-prong un-grounded plugs that go into the same power strip that then goes into the wall (using a 3 to 2 prong adapter for the power strip does not help at all).

Also disconnecting any TV or Antennas from the receiver doesn’t help either.

There is only one solution that clears the noise from the speakers…disconnect the power to my laptop and run on battery. But my computer is slower and I typically leave my computer on for 8-10 hours at a time so that solution is not practical.

So my question becomes what other (affordable) solutions can I try? I really don’t want to spend $100 dollars on one of those expensive surge protectors that eliminates all hum on any appliance. So what else can I try?

Any suggestions would be much appreciated.

GROUND-LOOPING PROBLEM

I have read a lot of forums on this, but for me, all the solutions given have not worked for me. I keep getting oud buzzing noise in my right speakers. Here is my scenario. I have a Macintosh Powerbook.

The audio out of the laptop goes into an M-Audio MobilePre (Audio Interface)

From there, White/Red RCA output cables WITH a ground-loop isolator connect to my Onkyo receiver.

From there the Onkyo receiver connects to 2-sets of speakers. Speaker set A and B.

Both my laptop and receiver have 2-prong un-grounded plugs that go into the same power strip that then goes into the wall (using a 3 to 2 prong adapter for the power strip does not help at all).

Also disconnecting any TV or Antennas from the receiver doesn’t help either.

There is only one solution that clears the noise from the speakers…disconnect the power to my laptop and run on battery. But my computer is slower and I typically leave my computer on for 8-10 hours at a time so that solution is not practical.

So my question becomes what other (affordable) solutions can I try? I really don’t want to spend $100 dollars on one of those expensive surge protectors that eliminates all hum on any appliance. So what else can I try?

Any suggestions would be much appreciated.You could spend $100 bucks on an airport express, but that only works with iTunes. Have you tried a different miniplug to rca cable? Also, contact M-Audio support for answers.

unfortunately I don't believe M-Audio can help. The reason is because if I bypass the M-Audio interface, and plug the cord directly into the computer (1/8" to RCA cable) the same buzzing sound still occurs. Only when I unplug the computer power cord does the sound go away.

Also I have tried different wires including monster cable.

I have 2 400w 4 channel amps when both are on - there is no hum once I turn on the receiver all speakers hum pretty loud. I have moved power around, different breakers,outlets,power protecters etc. I am using radioshack RCA to trimmed wires.

Anyone have any suggestions receiver in question is onkyo 805

Thanks

Have you tried this with just the amp and the receiver? In other words, are any other components hooked up including your TV?

No nothing else is hooked up just pre amp and amp

I recently unearthed an old, old Sony receiver (circa 1991) to hook up a new pair of Athena floor speakers to. You guessed it, I'm getting a nice hum that I can't get rid of (though it's more high-pitched, really). At first I thought it was a ground loop problem. So far I have:

-Unhooked every source from the receiver. Hum.

-Unplugged every device but the receiver in the entire living room, including lamps. Hum.

-Plugged in the receiver in a different room elsewhere in the apartment. Hum.

-Hooked a different pair of small computer speakers to the receiver with no sources connected. Hum.

-Hooked the Athenas up to the computer speaker sub to test them separately from the receiver. The computer sub was plugged into the same wall outlet as the receiver was originally. No hum (but nice music reproduction from my iPod).

I feel like all this points to a faulty component rather than a solvable ground loop issue. Given the extreme age of the receiver, I guess that's not too surprising. Does that sound like the logical conclusion to any of y'all (who are definitely more educated about this stuff than I am)?

If anyone concurs that the receiver is just going bad, I'll start shopping for a new one. :D Thanks!

rudds
You did a nice job troubleshooting.
Shop till you drop.

sfitzger
radioshack RCA to trimmed wires
Sorry, but I'm not sure what that means!

Question:

The most common ground in an A/V system is the third wire in the power circuit, which ties back into the main distribution panel. On mine it and the neutral (white) on 120V circuits both meet at the neutral bar.

Should the neutral bar tie directly to the house ground stake?

How does one prove that to be a solid connection?

In most building/electrical codes, the Neutral and Ground buss are tied together at the entry box. Separate N and Gnd wires go to each outlet, and there you can have a problem, with the way house wiring is "daisy-chained" one ground can get dropped, now you have not only a floating ground, but a shock hazard in addition to HUMMMM

You can purchase a ground tester. http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?jspStoreDir=hdus&catalogId=10053&productId=100062242&navFlow=3&keyword=ground+tester&langId=-1&searchRedirect=ground+tester&storeId=10051&endecaDataBean=com.homedepot.sa.el.wc.catalog.beans.EndecaDa taBean%4041c123d0&ddkey=Search

However, there's a way to ground the ground wire to the neutral wire on the wall socket. Just loop a small green wire from the ground hookup to the neutral hookup. This will create a grounded connection, but it's definitely not up to code and not advisable unless you must cheat.

I have 2 400w 4 channel amps when both are on - there is no hum once I turn on the receiver all speakers hum pretty loud. I have moved power around, different breakers,outlets,power protecters etc. I am using radioshack RCA to trimmed wires.

Anyone have any suggestions receiver in question is onkyo 805

Thanks


Be sure to keep power cords away from interconnects.

The other night while listening to a SACD (5.1) very loud (-5 dBto -3 dB on the relative scale) I detected a low level hum between tracks( I would describe it as 60 cycle) . I have had this equpment for 9 months and hadn't heard this before. I don't think I had listened at that volume level before After investigating I found that I can start to detect the hum at volume set at -10 dB (very faint), it starts to get annoying at 0 dB. I have an Onyko 705, Panny PX75U Plasma, Oppo 981, Motorola Cable Box/DVR and Panny BD30 all connected via HDMI. I read this furum and did some research on ground loops. I replaced my power outlet with a three prong and checked it with a ground checker. It is fine. My cable is grounded outside with a seperate wire like I have read it should be. If I set my Onyko to direct, bypassing the preamp section there is no hum. I then began to troubleshoot.I disconnected all 4 HDMI cables (3 in and 1 out), there was no hum. I then started to plug in the HDMI cables one at a time. The Onkyo volume at max. With 1 cable in the hum returned but lower in intensity, with 2 in the hum got louder, with 3 in still louder, the 4th the hum stayed the same. I then disconected the cable (coax) from the cable box and unplugged the power cords of all the components, the hum was sill there. It doesn't matter what order I plug the HDMI cables in the hum is there and presents in the same way. Since it is only SACDs that seem to have a lower volume output, which would make me push the Onyko for extreme volume listening seesions, I increased the preset levels on the Oppo by +5 dB. This sort of solves the issue since I don't need to put the volume up above -10 dB to achieve extreme levels. But you know how it is, knowing the hum is there bothers me. Does anyone have any ideas or suggestions? Are there isolators for HDMI cables. I would greatly appreciate any responces. Thank you.

That’s a first I haven’t heard of humming type like this before? I mean sure with separates linking off an AVR, but not when increasing the volume on the AVR I gather your using the internal power amplification stage on the AVR.

Try this quick simple method of taking a short or any length of cable, wire attach it to the screw fitting on the AVR then go around each item attaching it to the screw head once you have isolated the humming issue screw the wire to that item and lets hope you don’t get anymore humming issues

I am using the internal power. I will give the seperate wire technique a shot.

I am using the internal power. I will give the seperate wire technique a shot.

Well I hope it grounds the issue because I’ve used this technique many times.

That’s a first I haven’t heard of humming type like this before? I mean sure with separates linking off an AVR, but not when increasing the volume on the AVR I gather your using the internal power amplification stage on the AVR.

Try this quick simple method of taking a short or any length of cable, wire attach it to the screw fitting on the AVR then go around each item attaching it to the screw head once you have isolated the humming issue screw the wire to that item and lets hope you don’t get anymore humming issues

A friend who is an Electrical Eng suggested I leave the HDMI cables plugged into the AVR and disconnect them from the various components. This will check to see if the HDMI cables are the problem. He doesn't think it's a ground loop. I'll try both and report back tomorrow.

A friend who is an Electrical Eng suggested I leave the HDMI cables plugged into the AVR and disconnect them from the various components. This will check to see if the HDMI cables are the problem. He doesn't think it's a ground loop. I'll try both and report back tomorrow.

Question is does the HDMI make your life better and wholesome if not junk them and use the other route to get around the issue or maybe one of the leads is broken or just keep working the problem. One time I had ground loop that took 24 hours around the clock to solve I got the bags under the eyes to prove it LOL.

Question is does the HDMI make your life better and wholesome if not junk them and use the other route to get around the issue or maybe one of the leads is broken or just keep working the problem. One time I had ground loop that took 24 hours around the clock to solve I got the bags under the eyes to prove it LOL.

I believe the noise or hum I'm getting at max volume is RF induced. Using an SPL meter near a speaker and plugging in each of the HDMI cables I am using, one at a time, I measured as much as a 4 dB differance in hum/noise between cables, which I could hear, but it was nice to quantify. It turns out the cable producing the least noise was the no name cable that came with my Oppo 971. The differance between this cable and the others is it has RF chokes at the ends. I ordered up 3 cables with chokes and some add on chokes from Monoprice. All for under $20.00. The noisiest cables were 2 from Bluejean Cables about 4 dB higher than the no name. The other was an expensive Monster Cable at about 3 dB higher. I'll let you know what happens when I get the new cables. Do you think a power conditioner will help?

I noticed a hum in my system when I install 2 subs. I had a different one before and used a ground lead over to the pre/pro and it took care of the problem. With the new subs (JL Audio F112's) connected with balanced interconnects it hummed. Grounding didn't work, lifting the ground on the power cord didn't work. I bought one of the Ebtech hum eliminators and it worked pretty good but I still had some hum. Finally figured it was coming from my cable TV cable and played with the ground at the outside box. Still couldn't get it quiet. So I bought one of the Mondial M.A.G.I.C. Cable TV Isolators used on Audiogon. What a great product. Absolutely no hum and I removed the Ebtech hum eliminator and everything is dead quiet. The hum was embedded in my cable signal. So if your in a similar situation, I would recommend checking out the Mondial device.

I have a sunfire cinema grand 5 x 200 watts. All channels hum. I have:

1) removed all inputs
2) turned off all other components
3) tested different speakers
4) tested all outputs
5) tried shorting input during test
6) moved amp away from all other electrical components


In all cases, I cannot get rid of the hum. With just one speaker connected, I can hear it from 10 feet away. with L/C/R speakers connected, it's very obvious!

It looks like fixing this amp is a $700 flat fee from Sunfire. Is there anything else I can do to fix this? Should I use one of the line "conditioners" like Belken PF60 (would it be a good idea to have one of these anyway?)? As a last resort, could I put some passive crossovers on each of the outputs to cut out the 60Hz hum?

I definitely have this ground loop issue on my TV.

My concern is as follows- while I am figuring out how to solve this issue, can I in any way damage my Plasma if I use it? Generally, can a ground loop damage the component it is affecting?

I definitely have this ground loop issue on my TV.

My concern is as follows- while I am figuring out how to solve this issue, can I in any way damage my Plasma if I use it? Generally, can a ground loop damage the component it is affecting?

I've had two systems with ground loops. Both were caused by comcast cable lines. I resolved this by using a grounding block just before the the TV. My surge suppressor has a grounding lug. I grounded each component and made sure they were all connected to the same circuit. Obviously everyone's case is different, but you can try to see if you get anywhere with that method.

I definitely have this ground loop issue on my TV.

My concern is as follows- while I am figuring out how to solve this issue, can I in any way damage my Plasma if I use it? Generally, can a ground loop damage the component it is affecting?

My Panasonic Plasma has had this problem for four years, but don't worry you will not hurt your TV.

I bought the Viewsonics ground loop isolator and it removed about 85% of the problem and cleaned up the picture a bit. For $25 it is a simple solution and took about 5 min to install. Give it a try.

I recently redid my AV system to use pretty much all HDMI cables and removed some obsolete components. The result was a very annoying hum.

After some isolation, I determined it was originating in the Comcast cable feed and being distributed by the HDMI cables. Putting in a 3 to 2 prong plug to lift the ground from TV (the only component with a 3 prong plug) helped but didn't fix the problem, plus running completely without a ground worried me.

So I got a Jensen Transformers VRD-1FF on ebay, plugged it in, and POOF! the hum completely went away, even at high volume and no input. This has had no impact on the quality of the cable video including the HD channels. I don't use view on demand or any of the premium channels so I can't comment on those.

Worked for me.

NB - Read and follow the directions that come with it!

#2 says "see number 2". I can't get out of this thread!

Note:
I posted this response in the "Subwoofers, Bass, and Transducers" forum, http://www.avsforum.com/avs-vb/showthread.php?p=17154999#post17154999
but it should be part of this sticky as knowledge base info.

I recently redid my AV system to use pretty much all HDMI cables and removed some obsolete components. The result was a very annoying hum.

After some isolation, I determined it was originating in the Comcast cable feed and being distributed by the HDMI cables. Putting in a 3 to 2 prong plug to lift the ground from TV (the only component with a 3 prong plug) helped but didn't fix the problem, plus running completely without a ground worried me.

So I got a Jensen Transformers VRD-1FF on ebay, plugged it in, and POOF! the hum completely went away, even at high volume and no input. This has had no impact on the quality of the cable video including the HD channels. I don't use view on demand or any of the premium channels so I can't comment on those.

Worked for me.

NB - Read and follow the directions that come with it!




I had same problem, the cable people did a crappy job with grounding using cheap clamp, it had I think a bi-metallic corrosion going also as well. (wiggly clamp)

Before showing cable install job:
http://lh5.ggpht.com/_FqTNmgNQHz8/SkUPN9AITCI/AAAAAAAAF4U/t6U7MWqQ41c/s400/IMG_2424.JPG http://lh3.ggpht.com/_FqTNmgNQHz8/SkUPO1dW51I/AAAAAAAAF4Y/ADZ80TxUuJ0/s400/IMG_2426.JPG

I took the clamp off, went to HD, bought 6' copper wire, attached to inside home copper pipe, actually next to where the 200A main also had a ground wire attached.
Copper wire going into basement shown:
http://lh5.ggpht.com/_FqTNmgNQHz8/SkUOb9y4A_I/AAAAAAAAF30/3psetBdjgmQ/s400/IMG_2442.JPG http://lh6.ggpht.com/_FqTNmgNQHz8/SqmIfM4kUzI/AAAAAAAAHbI/Ge1yZIjUoOE/s400/IMG_3893.jpg

To make matters a little more complicated, my outside faucets are "isolated" and not really connected to my inside pipes, due to my whole home EcoSmarte system, which uses various plastic/assy stuf for flowmeters, electrodes, etc.
So I connected a jumper wire from my inside pipes to my outside pipes, just to have them on the same ground plane.
This pict shows my whole home H20 system, kinda complicated but great H20 for whole home.
http://lh5.ggpht.com/_FqTNmgNQHz8/R1Z9E4yDszI/AAAAAAAAAn8/0UmRTLqiVp4/s800/EcoSmartePlusSoftenerDec052007.jpg

I also made sure the OTA antenna ground plane was same datum.
Here is in construction phase showing the home 2 ground rods.
http://lh5.ggpht.com/_FqTNmgNQHz8/SGNaongLrAI/AAAAAAAACIU/5RoE2DcX2SE/s800/DSCN0922_2.JPG

Here is the OTA antenna being correctly grounded to the red circled one, it is visible just past hot tub cement pad.
http://lh3.ggpht.com/_FqTNmgNQHz8/SuoTijnWt7I/AAAAAAAAHr0/_uyrBT6kT9A/s800/IMG_4264.JPG

Showing OTA copper wire on LH going around the corner under deck, while the antenna lighting rod is grounded next to the elect meters.
http://lh3.ggpht.com/_FqTNmgNQHz8/SuoTjKn4qlI/AAAAAAAAHr4/pK-oY_4Jj98/s640/IMG_4270.JPG http://lh4.ggpht.com/_FqTNmgNQHz8/SGrdVIzJ7sI/AAAAAAAACKo/pdgB_pxY6sM/s288/DSCN4476.JPG

So, when solving ground loop issues you have to totally trace/follow your elect system and cable/sat/OTA/etc ground points.

For me, no more ground loop issue.
Maybe $12 max.

................but it should be part of this sticky as knowledge base info.NICE post. In the truest sense of the word.

I've got a pretty vanilla 2-channel setup that I have setup.

- Sony XBR3 40" LCD (4 yrs old?)
- Oppo DV-981HD
- Yamaha V665
- HD TiVo
- MacMini
- NHTPro A10 monitor speakers (powered by it's own amp)
- Everything is connected the same circuit
- I don't get cable, I have OTA signal non amplified

I'm using the Yamaha just as a preamp for the signal to the speakers.

I can be watching for hours, and then I starting hearing a hum, which goes away if I turn off the Sony LCD, the audio from all the components will be hum-free

Any thoughts on that? I've considered trying the test by cutting out the NHT Amp,and powering the monitors through the Yamaha, but I don't suspect any improvement. Could it be that the age of the TV?

Thanks in advance . . .

It most like caused due to transformer interference from the Inverter Board of your Sony LCD. Call up Sony and see if they have a fix.

Maybe someone can shed some light on an issue I have. I already sent this message to PSB, but haven't heard from them yet.

I have an odd issue with a "PSB Alpha SubZero i" that I picked up. It is apparently never used, just long stored.

Setup:
PSB Image B25 Bookshelves
PSB Alpha SubZero i
Marantz PM5003 Integrated Amp

The B25s are connected to the A terminals on the Marantz, and the SubZero is connected from the B terminals to the high level inputs on the sub.

When the subwoofer is powered on, and absolutely nothing is connected to it, it is silent. Once I connect the speaker cables to the Marantz (powered off), the subwoofer begins to hum (and the hum is dependant on the volume control). Once I turn on the Marantz, the hum goes away completely. If I turn off the B terminals, the hum returns, turn the B terminals back on, hum is removed.

I've already tried changing the speaker cables, changing the power cable, plugging the power in to a different surge protector and UPS, getting power directly from the amplifier, connecting the sub to the A terminals, but I can't remove the hum when it's not receiving a signal from the receiver. I even tried to short the low-level input terminals with some RCA cables cut and the ground->signal wires twisted together.

Thank you for any help you can offer.

I've been mostly a 2-channel guy until recently when I bought a receiver to set up a home theater in the basement. I have 3 dedicated circuits that I use for my home theater gear. There have been no humming problems when I use just the receiver or when I use just my 2-channel gear (ie. 2-channel amp, pre-amp, CD player). However, as soon as I connect an external 5-channel amp to the pre-outs of my receiver, I'm getting loud humming noise through the speakers and even the subwoofer.

At first, I thought it was a problem with my 5-channel amp. So I swapped it out for my 2-channel amp to power just the front left and right speakers through the receiver's pre-outs. Now, this 2-channel amp has a ground lift toggle switch. When I toggle it on, the hum disappears and I have bliss. When it's off, the hum comes back.

Is it a simple solution to buy a 5-channel amp with a ground lift switch? Or is it better to attack the heart of the problem and figure out if I have a ground loop problem? I could just use the internal amps of the receiver, but I notice a better sound if I use the receiver's pre-outs and add an external amp to the set-up.

Thanks for your help!

LPW

This is not uncommon in my experience, but usually a little trouble shooting solves it.

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
source and an interesting read: link (http://www.epanorama.net/documents/groundloop/)

You may have this condition with your 3 separate circuits. You could try putting them all on one surge supressor to see if it eliminates the problem. It it does, then one by one move them to another circuit, if that's what you desire, until it returns.

If the above doesn't work you can looking into the following.

Does your amp have a grounding terminal? If so, and you have a surge supressor that has a grounding terminal - for your equipment - try grounding your amp to that terminal.

Is your cable or satellite hooked up to your system? If so, you may need to add a ground it at the splitter or add a simple grounding block and ground it to your supressor.

I hope one of these solutions helps.

LPW

This is not uncommon in my experience, but usually a little trouble shooting solves it.


source and an interesting read: link (http://www.epanorama.net/documents/groundloop/)

You may have this condition with your 3 separate circuits. You could try putting them all on one surge supressor to see if it eliminates the problem. It it does, then one by one move them to another circuit, if that's what you desire, until it returns.

If the above doesn't work you can looking into the following.

Does your amp have a grounding terminal? If so, and you have a surge supressor that has a grounding terminal - for your equipment - try grounding your amp to that terminal.

Is your cable or satellite hooked up to your system? If so, you may need to add a ground it at the splitter or add a simple grounding block and ground it to your supressor.

I hope one of these solutions helps.

Thanks for your reply! I did some more troubleshooting tonight and found:

1) If I disconnect the coax cable going from my splitter to the wall plate where my cable box is connected, the hum is reduced considerably.

2) I have a 30 ft HDMI cable run in the ceiling connecting my projector to my receiver and when I unplug the HDMI to the receiver, this also reduces the hum, albeit only slightly. I wonder whether I ran this cable too close to the coax cable in the ceilng. It's a Blue Jeans HDMI cable recommended specifically for long runs.

3) When I have my HTPC turned on, I get terrible static sound through the speakers that I'm driving with the external amp as well as through the subwoofer. The static sound is much more annoying than even the ground loop hum! When I unplug the HDMI cable going from my HTPC to my receiver, the static sounds disappear. I'm using a monoprice HDMI cable.

All signs pointing to a ground loop problem? I also find that plugging the external amp to a circuit different from the receiver reduces the hum. I did try plugging both the receiver and amp into a power conditioner, but that didn't solve the hum. Unfortunately, my new 3-channel amp does not have a ground lift switch like my 2-channel amp and switching it on eliminates the hum when I use the 2-channel amp in this system.

What do you recommend I try next? I do remember that my cable company used a splitter on the outside cable box because they ran one coax into my basement and a 2nd one to the upstairs bedroom. Does this outside splitter affect things?

Thanks very much for your help!

Thanks for your reply! I did some more troubleshooting tonight and found:

1) If I disconnect the coax cable going from my splitter to the wall plate where my cable box is connected, the hum is reduced considerably.

2) I have a 30 ft HDMI cable run in the ceiling connecting my projector to my receiver and when I unplug the HDMI to the receiver, this also reduces the hum, albeit only slightly. I wonder whether I ran this cable too close to the coax cable in the ceilng. It's a Blue Jeans HDMI cable recommended specifically for long runs.

3) When I have my HTPC turned on, I get terrible static sound through the speakers that I'm driving with the external amp as well as through the subwoofer. The static sound is much more annoying than even the ground loop hum! When I unplug the HDMI cable going from my HTPC to my receiver, the static sounds disappear. I'm using a monoprice HDMI cable.

All signs pointing to a ground loop problem? I also find that plugging the external amp to a circuit different from the receiver reduces the hum. Unfortunately, my new 3-channel amp does not have a ground lift switch like my 2-channel amp and switching it on eliminates the hum when I use the 2-channel amp in this system.

What do you recommend I try next? I do remember that my cable company used a splitter on the outside cable box because they ran one coax into my basement and a 2nd one to the upstairs bedroom. Does this outside splitter affect things?

Thanks very much for your help!

Well without a doubt the outside splitter should be grounded, but that may not eliminate your problem with the cable and you ht setup. You could add an inline grounding block like the one I have in this picture

http://www.summitsource.com/images/products/GRB1HF.jpg

Just do that inside before it got to your tuner or whatever you have it plugged into. Ground that to your surge suppressor. If you're using a cable box, you might avoid this by plugging it into the same circuit as your amp and processor. That's the quickest fix. ;)

I'm running an HDMI cable to my projector which is 35ft and I don't have that issue. I'm gathering you used a cl2 rated cable?

What type of interconnects are you using, balanced or unbalanced. I've heard this can help, but not sure.

I think once you eliminated the main cause you'll start to be able to eliminate the rest. Is your HTPC next to your home theater equipment? If it's near a speaker or magnetic source that's not shielded you'll have issues.

Well without a doubt the outside splitter should be grounded, but that may not eliminate your problem with the cable and you ht setup. You could add an inline grounding block like the one I have in this picture

http://www.summitsource.com/images/products/GRB1HF.jpg

Just do that inside before it got to your tuner or whatever you have it plugged into. Ground that to your surge suppressor. If you're using a cable box, you might avoid this by plugging it into the same circuit as your amp and processor. That's the quickest fix. ;)

I'm running an HDMI cable to my projector which is 35ft and I don't have that issue. I'm gathering you used a cl2 rated cable?

What type of interconnects are you using, balanced or unbalanced. I've heard this can help, but not sure.

I think once you eliminated the main cause you'll start to be able to eliminate the rest. Is your HTPC next to your home theater equipment? If it's near a speaker or magnetic source that's not shielded you'll have issues.

I took a photo of my outside cable box and traced a black cable (thinner gauge than the coax cables) that leads down and to the left (see photo below). Someone mentioned to me that this is probably the ground wire. Well, this cable ends unterminated and not attached to anything on the outside wall. So, if this is in fact the ground wire, then it's safe to say that I have an ungrounded cable wire??

If this is the case, I'll call my cable provider and see what they say. Where can they ground this wire though? They're not going to have to dig up my driveway to do this, are they?

http://i478.photobucket.com/albums/rr149/highroller54/cable.jpg

If you have any pole going into the ground, that should work. However, I wouldn't be too concerned about it. Just get a grounding block or splitter and ground it before your equipment - in your house - which you may have to do anyway.

You can do this as well: http://www.ehow.com/how_2076406_ground-tv-cable-line.html
Here's a discussion on avsforum: http://www.avsforum.com/avs-vb/showthread.php?t=1128083

If you have any pole going into the ground, that should work. However, I wouldn't be too concerned about it. Just get a grounding block or splitter and ground it before your equipment - in your house - which you may have to do anyway.

You can do this as well: http://www.ehow.com/how_2076406_ground-tv-cable-line.html
Here's a discussion on avsforum: http://www.avsforum.com/avs-vb/showthread.php?t=1128083

Thanks for the links. I've been doing a lot of reading and troubleshooting but I haven't found a solution yet. I called my cable company and they sent out a technician who connected a ground wire from the splitter on the outside of the house to a grounding clamp attached to my hydro meter as shown in the pic below:

http://i478.photobucket.com/albums/rr149/highroller54/cable_ground.jpg

This actually eliminated the hum I was getting from my two TV's that use a set top box. It did not, however, eliminate the hum and static noise I'm getting from my 2-channel (amp + preamp) and home theater (receiver + amp through receiver's pre-outs).

I then investigated the house ground and found the grounding wire coming out of my electrical panel, which goes up into the ceiling and which I assume comes out at the other end of the room where it is clamped onto the water pipes (see pic below). Now, the coax cable coming into the house feeds into a splitter - should i attach a ground wire to the ground wire coming out of the electrical panel? Would this create the "common ground" and eliminate ground loops?

http://i478.photobucket.com/albums/rr149/highroller54/cable_ground2.jpg

I also bought a Viewsonic VSIS ground loop isolator (similar to the Jensen VRD-1FF), but it didn't have any effect on the hum.

Grounding to a copper pipe is normal in my experience, but I'm not an electrician. I'm just going by what I've commonly seen

Are your components all plugged into the same surge suppressor or outlet?

What about you sub woofer? `

Do any of your components have a grounding lug and are they in use?

When you disconnect your cable/satellite does the hum go away?

Thanks Dr Spike! Any suggestions for a replacement lamp? Should I go for say, a flourescent lamp?



DogBean,

A candle is your best bet.

I'm having a tough time getting rid of a ground loop hum in my home theater, and I'm looking for some tips.

My theater consists of:
- Denon AVR-2809 (2 prong power cable)
- Rotel RMB-1075 (2 prong power cable)
- Epson 1080UB projector (3 prong power cable)
- Sony blu-ray player (2 prong power cable)
- PS3 (3 prong power cable)
- Xbox 360 (2 prong power cable)
- Wii (2 prong power cable)
- Squeezebox (2 prong power cable)
- SVS Sub (3 prong power cable)
- Satellite receiver

With just that equipment everything was working great. No issues. Everything is run off the same circuit, but due to the location of the projector and sub, they are off a different outlet. I have moved them closer and tried off the same outlet, without success. Everything else is plugged into an APC Power Bar.

I added a Wyred 4 Sound DAC-2 in the hopes of improving my 2 channel experience, and now I've got a hum.

I'm using the HT bypass feature, so my front left and right go through the DAC, then to the Rotel. My surrounds and centre go direct from the Denon preouts to the Rotel.

I can make the hum disappear by disconnecting the HDMI cables for the projector, PS3 and satellite. If any of those are connected it will hum. I've completely removed the satellite from the equation (coax unplugged, HDMI unplugged, power unplugged) and it will still hum with the PS3 and/or projector, so it's not just ungrounded coax.

I can also make the hum disappear by disconnecting the interconnects for the surrounds and centre channels to the Rotel.

Lastly, if I use a cheater on the DAC power cable, the hum is gone.

Any advice on what to try? Since the cheater works, what would be a safe alternative, since I know cheaters are not to code, and am not interested in something that could be a potential risk.

I've tried grounding the Denon to the outlet, with no success. I'm really at a loss as to what to try.

Thanks,
Tyler