Humming sound when playing TV (2 Viewers)

[Dale#1976]

I have a humming sound in the background when I play my TV through MP. This also was there with MS Media Center.

Sound is input through the RCA jacks to the TV tuner card and sound is output to a Yamaha 7.1 amp using the SPDIF, but I also hear the hum through the computer speakers too.

Got hum with Haupagge 150MCE tuner card so I went to an ATI 550 pro card. Only slightly less hum with the ATI, but it is still there.

Bought Creative X-FI card. Fantasic sound when playing music, but hum still in background when watching live or recorded TV.

Would love to use the SPDIF output from my Satelite receiver but when I input it through the X-FI card the TV sound is on all the time and is not in sync with the video. There is no hum when using the SPDIF output on sat. receiver.

Are there any TV tuner cards which have the SPDIF input right on the tuner card itself? This would allow the tuner card to control the digital sound input, I would assume.

Am I the only one who has this problem because I have searched all the forums and can't find anyone else complaining of this annoying hum in the background of all their TV and recorded TV programs.

Any suggestions for getting rid of the hum?

Thanks!!

Dale

 

[NLS]

check your ground

inc. your antenna ground

 

[Dale#1976]

Thank you for your suggestion.

I checked the wall socket and the powerbar with a tester. The tester has 3 lights which come on in various combinations to indicate an open ground or reversed wires etc. They show the wiring of the wall sockets and grounds are correct. I changed the power cable from the powerbar to the computer thinking that might make a difference, but it didn't.

I am using a satelite receiver, so there isn't any ground on that except through the power cord. No antenna.

Is there a simple way to make sure the computer (power supply) is properly grounded?

Thanks again!!

Dale

 

[Taipan]

Sound is input through the RCA jacks to the TV tuner card and sound is output to a Yamaha 7.1 amp using the SPDIF, but I also hear the hum through the computer speakers too.

I assume you mean that you have the analog audio output of your satellite receiver connected to the PC via the RCA sockets (red and white plugs) on the TV card?

If that is correct, then it sounds like you may have an "earth loop" causing the hum. This could be caused by both the satellite receiver and the PC being earthed via their mains sockets. Only one of them (or better still, neither of them) should be earthed as you also have the satellite box earthed to the PC via the braid on the audio lead.

To see if an "earth loop" is the cause, you need to disconnect the earth connection (to the power plug) on the satellite receiver or the PC - which ever is easier.

HTH ....

 

[Dale#1976]

Thankyou Taipan:

Yes, I am using the red and white RCA audio inputs to the TV tuner card.

That sounds interesting, but how do I 'disconnect the earth connection to either the satellite receiver or the PC. I thought the three prong plug automatically grounded both the receiver and the PC.

Sorry, but I am no electrician and I'm not sure how I would 'unground' either. I thought most electronic devices needed to be grounded to prevent a buildup of static, particularly with computers and hard drives ....

Can you expand on your responce?

Thanks .... Dale

 

[Taipan]

how do I 'disconnect the earth connection to either the satellite receiver or the PC. I thought the three prong plug automatically grounded both the receiver and the PC.

Yes, the 3-prong plug will usually ground the device.

Do both your PC and satellite receiver have 3-prong plugs? If the satellite receiver has only a 2-prong plug, then it will not be grounded via the mains and an earth-loop is not the cause.

I am not familiar with Canada's electricity standards, so I am not sure what to suggest that you could do (safely) that would break the earth loop.

Is the power-lead on the satellite receiver fully moulded, so you cannot open it up and disconnect the earth lead?

Is the power-lead on the satellite receiver removeable (plugged into the back of the receiver), so you could replace it with a 2-pin lead?

I thought most electronic devices needed to be grounded to prevent a buildup of static, particularly with computers and hard drives ....

No, the purpose of the earth connection is for safety - if the device develops a fault such that the mains active is connected to the case, then the earth connection will prevent a user from getting an electric shock. But, usually electronic equipment is 'double-insulated" and not earthed, to prevent these audio "earth-loops".

 

[NLS]

in any case this looks like a case for the common (or the bit more advanced) electrician... call one at home

 

[Dale#1976]

Hello Taipan:

In Canada all wall sockets are 3 prong. The computer has a 3 prong plug while the satellite receiver is only a 2 prong plug. Guess that means there probably isn't an earth-loop.

Is it possible to have the opposite problem and get a hum? If the power supply in the computer was not properly grounded internally, then would that cause the hum? Maybe the problem is that neither the computer nor the satellite receiver are grounded.

I've been having problems rebooting the system if I don't turn the powerbar off and let it sit for a few minutes. It is like the system has to 'discharge' or something before it will reboot. I've suspected that the computer may not be properly grounded but I haven't had a chance to take in and get it checked.

Just found an article on the web which explains the earth-loops in a very simple manner. It is here:

http://www.jaycar.com.au/images_uploaded/humloop.pdf

NLS, you are probably right, maybe I should call an electrician.

Thanks for the info. It gives me an avenue to follow.

I'll let you know if I manage to solve it.

Dale

 

[Dale#1976]

Has anyone used one of these Ground Loop Isolators? Do they work and do they effect the audio quality?

http://www.xitel.com/customerdata_pdfs/GLI.pdf

If you've used one of these can you please comment on how well they work.

Thank you .... Dale

 

[Taipan]

The computer has a 3 prong plug while the satellite receiver is only a 2 prong plug. Guess that means there probably isn't an earth-loop.

Yes, that would be my conclusion too. So I don't think that a "ground-loop isolator" will help.

Given that the hum is coming in on the audio line from the satellite receiver, it could be a fault in the satellite receiver that is putting hum on the audio outputs. Can you plug the audio leads from the satellite receiver into a TV or your audio amplifier to see if the hum is still there?