Interference on stereo from cable box

Lennoxschips

Hi,

I have recently purchased a DVB-C box. Am very happy with the picture quality, hooked up to my computer monitor through a spare HDMI port.

For sound I hook the red/white RCA ports on the DVB-C box into my stereo system.

Only problem is, I hear a slight "humming" sound on the stereo system now, even when I turn the volume all the way down. This is also present when I select another source on the stereo amplifier (e.g. CD player).

However, I discovered that if I disconnect the coax cable from the DVB-C box, then the humming noise goes away!

Is this the case of a badly designed box? I.e. the signals inside the box not being properly shielded?

Is there something I can buy to filter the signal from the coax? I have no knowledge on this subject. An attenuator or something?

Any tips would be greatly appreciated. At the moment I have to disconnect my DVB-C box from the coax cable whenever I want to enjoy music on my stereo... and then reconnect to watch TV (with a humming noise in the background).

Lennoxschips

Do I need one of these??



(And shouldn't it be built into my DVB-C box?)

Antenna

Lennoxschips wrote: »

However, I discovered that if I disconnect the coax cable from the DVB-C box, then the humming noise goes away!

Its a ground loop problem.

http://siber-sonic.com/electronics/GLoopwhatis.html

Connect the coax cable through an isolated outlet to that DVB-C box.
An isolated socket will have capacitors on the little circuit board on the back.

There is slight signal loss with isolated (compared to non-isolated) sockets so only use them where its necessary

The cable company might give you one for free if you explain the problem!

not 100% sure if the thing in the picture will do what is required.
If you have a multimeter - an isolater will have a very high or infinite resistance reading from input to output - for both coax outer and inner.

Lennoxschips

Thanks for the tip, but what exactly is an isolated outlet?

Bear in mind I am renting so can't change anything...

Antenna

Lennoxschips wrote: »

Thanks for the tip, but what exactly is an isolated outlet?
..

It is to block any mains (50/60Hz) current (as well as DC) on the cable, whilst passing VHF/UHF.

Put one in-line on the connection to the STB (rather than change your outlet)