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Audio Theory, Setup, and Chat > Hum FAQ
HooStat's Avatar HooStat 11:48 AM 12-17-2004
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.

Chu Gai's Avatar Chu Gai 07:48 PM 04-23-2005
Hum & Buzz in Unbalanced Interconnect Systems is a rather short pdf download.
vgs86's Avatar vgs86 07:28 AM 05-27-2005
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
hmgerard's Avatar hmgerard 09:08 PM 07-25-2005
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
3D Guy's Avatar 3D Guy 02:47 PM 08-24-2005
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.
k2koq's Avatar k2koq 07:54 AM 09-11-2005
cneely8's Avatar cneely8 09:58 AM 11-09-2005
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.
All Wired Up!'s Avatar All Wired Up! 12:56 PM 11-25-2005
Quote:
Originally Posted by DrSpike69 View Post

First you should have one of these 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.

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.
gonzalc3's Avatar gonzalc3 10:18 PM 11-28-2005
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
dxh's Avatar dxh 11:12 AM 12-10-2005
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.
Andre Smith's Avatar Andre Smith 09:10 AM 03-04-2006
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?
vett93's Avatar vett93 11:04 PM 07-27-2006
Quote:
Originally Posted by HooStat View Post

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?
shamus's Avatar shamus 02:48 PM 08-15-2006
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.
Keenan's Avatar Keenan 03:36 PM 08-15-2006
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
shamus's Avatar shamus 04:45 PM 08-15-2006
thanks!!!
FreeBaGeL's Avatar FreeBaGeL 04:36 PM 08-27-2006
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?
jws43yale's Avatar jws43yale 08:32 PM 09-27-2006
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.
Keenan's Avatar Keenan 01:56 AM 09-28-2006
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/in...entPage=search
RadioShack.com - Car: Accessories: Car A/V accessories: Ground Loop Isolator
HardStyle's Avatar HardStyle 11:48 AM 11-01-2006
was very helpfull thanks
Schwingding's Avatar Schwingding 11:50 AM 11-02-2006
Quote:
Originally Posted by jws43yale View Post

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.
swest's Avatar swest 08:24 PM 11-06-2006
Quote:
Originally Posted by vett93 View Post

Quote:
Originally Posted by HooStat View Post

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/showt...&&#post8831624 and following). I called back to B&K today to get a second opinion on this solution, and they confirmed its acceptability. Thoughts?
kiwi2000's Avatar kiwi2000 02:22 PM 11-10-2006
Quote:
Originally Posted by keenan View Post

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/in...entPage=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?
Keenan's Avatar Keenan 04:26 PM 11-10-2006
Quote:
Originally Posted by kiwi2000 View Post

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/in...entPage=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.
swest's Avatar swest 07:02 PM 11-10-2006
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.)
Keenan's Avatar Keenan 07:08 PM 11-10-2006
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.
Tnedator's Avatar Tnedator 10:42 PM 11-11-2006
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
Keenan's Avatar Keenan 10:23 AM 11-12-2006
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.
Tnedator's Avatar Tnedator 11:07 AM 11-12-2006
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?
Keenan's Avatar Keenan 11:28 AM 11-12-2006
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.
Winkelmann's Avatar Winkelmann 06:52 AM 11-22-2006
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
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