Buzzing sound from subwoofer (ground loop), what is the best solution?

[ougrad02]

Glad you got it worked out.

 

[j_garcia]

Well, you know what they say...

 

[mtrycrafts]

You can't use an isolator with a satellite system, as it won't pass the phantom DC powering voltage.

Is this how they eliminated the extra cables from sat dishes?

 

[MinusTheBear]

One quck question, the compenent cable (TV to DVD Player) that was causing the hum in the subwoofer was a cable that was supplied with the HD cable box. It is a cheap component cable no doubt, I assume the cable is not shielded properly which caused this. Can somone explain technically what was going on when that cable was connected to the system and why it would hum in the sub and not the speakers or both?

 

[j_garcia]

This one should answer what you are looking for:

http://www.audioholics.com/tweaks/connecting-your-system/ground-loops-eliminating-system-hum-and-buzz

Another way I have seen this remedied is to run a ground wire from each device to the ground on the receiver or from each to a common (verified) earth ground.

 

[TLS Guy]

Is this how they eliminated the extra cables from sat dishes?

Yes the signal feed provides the DC power, just like the studio condenser mike system.

The snag is you can't split the signal or use any transformer type device in the signal path.

The Direct TV HD DVR has 13 volts on one cable and 18 on the other. There is also a pulse signaling system to activate the multiswitch.

 

[TLS Guy]

One quck question, the compenent cable (TV to DVD Player) that was causing the hum in the subwoofer was a cable that was supplied with the HD cable box. It is a cheap component cable no doubt, I assume the cable is not shielded properly which caused this. Can somone explain technically what was going on when that cable was connected to the system and why it would hum in the sub and not the speakers or both?

Ground loops occur when there is a voltage between grounds. There is obviously a potential between your sub and the TV box ground. The current is flowing in your sub shield and inducing the buzz.

 

[Alex2507]

One quck question, the compenent cable (TV to DVD Player) that was causing the hum in the subwoofer was a cable that was supplied with the HD cable box. It is a cheap component cable no doubt, I assume the cable is not shielded properly which caused this. Can somone explain technically what was going on when that cable was connected to the system and why it would hum in the sub and not the speakers or both?

Even though I'm just starting to wonder about how this stuff works, I'm going to make a guess about what you had happening: Due to a fault in your component interconnect, interference was being generated @ a frequency that your sub responded to. I don't think 'ground loop' is the issue here at all. What are you using to connect your sub? At least now there is a statement to pick apart in hopes of teaching those of us who would benefit.

 

[j_garcia]

I doubt the cable was causing interference, since it is a passive component. The issue lies in one of the components connected with that cable.

 

[MinusTheBear]

Even though I'm just starting to wonder about how this stuff works, I'm going to make a guess about what you had happening: Due to a fault in your component interconnect, interference was being generated @ a frequency that your sub responded to. I don't think 'ground loop' is the issue here at all. What are you using to connect your sub? At least now there is a statement to pick apart in hopes of teaching those of us who would benefit.

I am using Blue Jeans Cable LC-1 Analog Audio Cable to connect LFE on sub to sub pre-out on receiver.

 

[MinusTheBear]

I doubt the cable was causing interference, since it is a passive component. The issue lies in one of the components connected with that cable.

For video, the component cable (stock cable that came with HD box) was connected from the t.v (3 prong) to dvd player (2 prong). For audio I have a Blue Jeans cable Belden 1694A Digital Audio Cable from DVD player to receiver (2 prong) for sound. The only other device that is 3 prong is the subwoofer in which the buzz was coming from. With the HD box (2 prong), the connections I have running is a Blue Jeans cable BJC Series-1 Belden Bonded-Pair HDMI Cabl (DVI to HDMI), RCA to 3mm from HD box to t.v, and a BJC optical cable from HD box to receiver.

 

[TLS Guy]

For video, the component cable (stock cable that came with HD box) was connected from the t.v (3 prong) to dvd player (2 prong). For audio I have a Blue Jeans cable Belden 1694A Digital Audio Cable from DVD player to receiver (2 prong) for sound .

The cable is not the issue! The issue is the voltage between the grounds to which the units are connected.

 

[Alex2507]

I doubt the cable was causing interference, since it is a passive component. The issue lies in one of the components connected with that cable.

How about if the center conductor has a break that causes a connection of varying effectiveness? Would that cause some sort of feedback? Kind of like what is described in the article you linked regarding outlets with worn out inards. I had an electrician start explaining something along those lines to me at work. I didn't get a full grasp of the concept though. Enough out of me talking about things I don't understand. It just seems that if one of the components was bad, changing the wire wouldn't fix it.

I am using Blue Jeans Cable LC-1 Analog Audio Cable to connect LFE on sub to sub pre-out on receiver.

Nice cable. IIRC there is one type of interferance that it won't guard against, right? I forget which one. We'll get to the bottom of this yet.

 

[TLS Guy]

How about if the center conductor has a break that causes a connection of varying effectiveness? Would that cause some sort of feedback? Kind of like what is described in the article you linked regarding outlets with worn out inards. I had an electrician start explaining something along those lines to me at work. I didn't get a full grasp of the concept though. Enough out of me talking about things I don't understand. It just seems that if one of the components was bad, changing the wire wouldn't fix it.



Nice cable. IIRC there is one type of interferance that it won't guard against, right? I forget which one. We'll get to the bottom of this yet.

Stop thinking so much. Ground loops are always due to current flowing between grounds at different potential. There is nothing else to say. That is what the are pure and simple. The rest of this thread is noise.

 

[Rickster71]

Stop thinking so much. Ground loops are always due to current flowing between grounds at different potential. There is nothing else to say. That is what the are pure and simple. The rest of this thread is noise.

Absolutely!
We've been down this road many times; have to start saving the posts.

 

[MinusTheBear]

Absolutely!
We've been down this road many times; have to start saving the posts.

Maybe you have, but many others and myself included have not. Ground loops are all new to me, so this thread was not just "noise". I found all this information quite helpful.

 

[Alex2507]

Maybe you have, but many others and myself included have not. Ground loops are all new to me, so this thread was not just "noise". I found all this information quite helpful.

I'm pretty sure Rick is being sarcastic. 'Save the posts' ?
That was my first clue.
TLS is just codgedy. But probably right as usual.

 

[Alex2507]

Stop thinking so much..

I get that alot. It has yet failed to offend me on some level or another.

Ground loops are always due to current flowing between grounds at different potential. There is nothing else to say. That is what the are pure and simple. The rest of this thread is noise.

Your opinion of the rest of the thread is noted but the simplicity of ground loops is still lost on me. Let me say that I don't understand how there is any current at a ground point to begin with. I take it potential means voltage. I'm sure there is a real number for this and what follows is not it. Would one ground point have 1 volt and another have 2 volts? So as the current that flows for them to become 1.5 volts is the ground loop? and it causes noise how? Hopefully the ?'s are indicative of why I don't get this.

I would just like to get my mind around it once and for all. I'm pretty sure the OP wouldn't consider this noise. I'm think we're a couple of guys who are trying to understand a thing.

 

[TLS Guy]

I get that alot. It has yet failed to offend me on some level or another.



Your opinion of the rest of the thread is noted but the simplicity of ground loops is still lost on me. Let me say that I don't understand how there is any current at a ground point to begin with. I take it potential means voltage. I'm sure there is a real number for this and what follows is not it. Would one ground point have 1 volt and another have 2 volts? So as the current that flows for them to become 1.5 volts is the ground loop? and it causes noise how? Hopefully the ?'s are indicative of why I don't get this.

I would just like to get my mind around it once and for all. I'm pretty sure the OP wouldn't consider this noise. I'm think we're a couple of guys who are trying to understand a thing.

The voltages are smaller than that as a rule.

If you take a big metal spike and drive it five feet down in the Earth, then you can take that as true ground.

However wires all have resistance. So there is significant resistance between the ground pin in each household receptacle and the house ground. (the wires are usually quite long).

Now let us say we have a cable system, notorious for poor grounds, that is at potential A. Now lets take a receiver sharing a circuit with other devices all leaking a bit of current to ground. Because of the resistance in the wiring to true ground, that ground will now be at potential B and different to A.

Lets add the sub, also leaking a little current to ground, and sharing the ground with other household devices and lighting on the same circuit. We now have potential C, different from A and B. They are all different because the resistance to true ground will be different for each as will the current leaked to ground, creating the different voltages. It takes very small potentials to generate enough current in the interconnecting cables to give a buzz! Nothing needs to be drunk eaten or snorted.

I trust this is a sufficiently cranky and codgedy post to get you through the day Alex. It never is a good idea to try and humor an Englishman too early in the morning. My countrymen have spilled a lot of ink, about getting told by a waitress to "have a good day" after eating breakfast in the US.

 

[Rickster71]

Maybe you have, but many others and myself included have not. Ground loops are all new to me, so this thread was not just "noise". I found all this information quite helpful.

I'm more than happy to help anyone that I can.

My comment, "have to start saving the posts" was directed toward myself. Being a slow typist, and realizing that I'd have to type a long explanation on grounding( as TLS did); and the process of elimination that goes along with it. I made a "note to self" kind of thing.
Though with that being said; the search function seems to be under utilized. I'd like to suggest using the search function, then asking a question to help fill in the blanks. Anyone is more than happy to help.

If (note the IF) TLS is codgity it could be that he has answered many questions, multiple times, only to have a member speculate as to some other cause/effect. I'm not singling out anyone in this thread; it has happened many times in the past.

I'm always willing to help, if the question falls within my limited expertise, electrical work, and women...... My wife informs my I know (very) little of the later.