TV Buzzing Sound

[jimlau]

I have the Samsung UN40EH5300F HDTV.

My tv is making a buzzing sound only when my cable (analog) and computer (via HDMI only) are both connected, even with my computer off.

Here's when the tv works, no buzz sound:

a) cable coax and HDMI blu-ray player connected to TV
b) computer connected to tv through HDMI (the coax is connected, but i do not choose tv as the input to display)
c) cable coax with computer connected via an ethernet cable.

It's when i try to watch coax cable tv with the computer connected with the HDMI. Even when the power to the computer is cut, if i just touch the hdmi cable to the computer's metal back panel the noise can be heard. (I even touched the HDMI cable to 2 other computers that were off, but plugged in)

So it seems the HDMI cable works (see a, b).

The tv speakers are fine (see a, b, c).

The computer HDMI port works (see b).

So what could it be? Some grounding problem? If relevant, my TV has only 2 prongs.

 

[nukemaster]

Low humming sounds are common ground loop issues. It should not hurt anything.

They do make isolators for the coaxial cable that may eliminate or greatly reduce it.

I have a very quiet hum on my speakers when my coaxial cable is connected to the pc via my tv card as well. Lucky for me it is very faint and can not be heard at normal volume levels. It is louder on the recorded tv however(not sure if it the ground loop or just the cable box it self.).

The first thing to try would be a coaxial isolator(it is effectively a transformer that breaks the connection between the 2 and still passes signal by way of a magnetic field.).

Read the reviews before getting on as some users report issues with some of the cheaper ones.

I can also get this noise by connecting 3 computers(with a mixer to keep the signals separate) to the same speakers(its MUCH worse this way and I do NOT do it.).

 

[avjguy2362]

The real problem is that your cable system is not properly grounded to your houses main circuit breaker. It is a very common problem. You can call you cable company and complain and they will come out and properly re-install the ground wire to a better spot. Cable company's can be very lazy about this and you know they have a lot of young kids who are usually in a rush to install your cable in the first place. If you live in an apartment you are usually screwed, but the ground loop insulator that Nukemaster mentioned will usually work or significantly reduce the ground loop hum. Try calling them and see if they will give you one, if not they are about $10 at Radio Shack.

 

[jimlau]

cable company said it is grounded, since my tv works when the pc is not also connected. not sure how the ground loop insulator works. where in the system does it go?

 

[nukemaster]

I am almost sure all cable is "grounded"

Simply put not all audio grounds are actually ground.

This thing(my mixer for the computers[lets 2 systems share an analog 5.1 speaker set], it is on a board and in a case now) for instance has a "ground"(0 volt potential) that is at 9 volts(a voltage divider lets me get a + and - voltage this way, but in reality its "ground" is not "ground"[earth]). It is "ground" to its own system, but in reality it sits at 9 volts allowing the audio to swing above and below that point to push the speakers forward(+) and backwards(-).

The problem is simply put the PC uses actual EARTH for ground(hell it may be using neutral for all i know, that goes to ground in the panel anyway) while many some audio devices may use a different grounding point. My cable line is firmly connected to the power mast(that us grounded).

Simply put, not all grounds are the same.

The ground loop isolator would go between the cable and the tv it self. Again. since it is just a transformer it provides isolation from the cable line to the tv. It has 2 coils, one takes the incoming signal and creates a magnetic field from it while the other takes that magnetic field and turns it back into the exact same signal(maybe a small bit of loss. the better the isolator, the less loss). This means that the ground from the 2 systems NEVER touches.

This problem can also happen when connecting to computers to the same speakers(even when only one is playing together. all the audio "grounds" are tied together in this system.)

I hope this clears it up a bit(it is almost impossible to eliminate ground loops with so many devices connecting unless all devices are VERY well built[or you use balanced equipment ].).

Just to make sure you have your issue location. If you connect everything and JUST pull the coaxial cable, the problem goes away?

 

[jimlau]

will look to buy one. yes, problems go away when I have my computer or my blu ray player connected and I choose them as input into the tv. the tv is actually still connected, it's just I don't choose it as source for display. so I don't have to disconnect the coax for the noise to not be there. it's only when I choose cable as my source.

actually the blu ray does not seem to cause nearly as much noise as the computer connection does when choosing cable as source, but if I crank up thevolume, there is some noise.

 

[nukemaster]

Well, please let us know how the battle goes.

Seems more easy to try to isolate the coaxial cable then everything else.

I would need 150+ dollars of transformers to isolate what I have. I am tempted to try a coaxial isolator as well, but need to find one that will NOT interfere with my digital cable.

 

[jimlau]

I found 1 possible device, the Viewsonics VSIS-EU Cable TV Ground Loop Isolator.

not sure if relevant, but my surround sound system, which is only connected via a digital audio cable to the cable box (i.e. not connected to the tv) has no hum.

 

[nukemaster]

It may just be better built. And remember that the digital part may not even care about the hum because it just looks for 1's and 0's. With a good setup for the digital to analog converter, it may be fixing problems for you.

If you want to go the group loop isolator route, please contact your cable provider to ensure that the frequency range of that isolator will cover all the channels you are using(100Hz up to 860MHz for the isolator you mention).

 

[jimlau]

not sure if relevant, but I plugged the tv into the same extension cord my computer is plugged into, but no change. not sure if that meant they have the same ground or not.

I also tried a second HDMI cable, but no luck.

 

[jimlau]

ah-hah. I think problem mostly solved. forgot to update the firmware. there is still a slight hum, but very faint unless I crank the volume.

I do have a bit of static noise with and without the computer, but again, only noticeable on hi volume. that may be due to a 25' coax feeding in the picture and sound.

 

[nukemaster]

What firmware did you update?

 

[jimlau]

it was the latest download from Samsung. I wish 1 of the first 4 people from Samsung had told me.

 

[nukemaster]

would be nice.

Good to see they have an actual update to fix/reduce this issue.