Nasty noise when connect my soundcard to home theatre

S

sloncho

Guest
Hi,
I have Panasonic SC-HT700. Here is a link to it's manual, if it can help :)
<http://service.us.panasonic.com/OPERMANPDF/SCHT900.PDF>

So, my problem is that if I connect my sound card to Panasonic AUX or line-in input, there is very annoying noise.

I tried both with line-out and phone outputs of the card.

The aux and line-in inputs seems to be ok, as I use line-in with my cable box, and also I have tried the aux input with my other DVD player. And there is no noise.

When I connect speakers to my sound card, there is no noise as well.

So, I thought that maybe the case or the card (it is onboard) are not well screened and this can cause the noise.

But I tried with some other cards, on different computers, both with onboard and PCI cards, and always there is a noise.

After all I gave up, and bought USB Soundblaster MP3+. Ans still, there is a noise.

The strange thing what I noticed is, that when I unplug my laptop from the power supply, the noise is dramatically lowered (still does not disappear completely).

So I guess there is something with the electricity, but I don't know what.

Does someone has any clue what to try next?

The bad part is that this Panasonic unit does not has digital input, so I can not use the digital output of the sound card (I guess this should solve the problem).

So, please, any advises. Will surge protector or UPS help?

Thanks
Sunny

P.S. This noise exists even if I connect the soundcard to the TV (also Panasonic, if this matters).
 
Hi :hiya:

Need some more info ... what sort of noise? Hum? Hiss? Crackling?
 
like HUMMMMMMMMMM, or UUUUUUUUUUU. It's permanent, not changing noise (of course it changes with the volume though).

Thanks
Sunny
 
Sounds suspiciously like an earth loop.

This can happen when you connect audio equipment together and use different mains sockets. What happens is that the earth wire comes out of one socket and connects via the earth shield on coax cables etc. to equipment plugged into the other wall socket, thus there's a 'loop' in the earth wire which induces a 50hz hum (50hz is the main frequency).

Ideally you want to connect all equipment into a single socket .. main 'protectors' in my experience can't eliminate this problem.

Note that using even a single socket will create a small loop but these rarely cause problems , ideally only a single piece of equipment should have its' earth lead connected to a plug, but that's potetntially dangerous of course if the earth link breaks elsewhere in the connection.
 
KraGorn said:
Sounds suspiciously like an earth loop.

This can happen when you connect audio equipment together and use different mains sockets. What happens is that the earth wire comes out of one socket and connects via the earth shield on coax cables etc. to equipment plugged into the other wall socket, thus there's a 'loop' in the earth wire which induces a 50hz hum (50hz is the main frequency).
<snip>

Note that using even a single socket will create a small loop but these rarely cause problems , ideally only a single piece of equipment should have its' earth lead connected to a plug, but that's potetntially dangerous of course if the earth link breaks elsewhere in the connection.

Hmm, then I'm beaten? As I'm using cable Internet, and my computers are on a different sockets, there will be always this problem, because always will be a earth loop through coax tv cable between the computers and the cable box?

Or I'm wrong?

Thanks for the help
Sunny
 

The latest video from AVForums

TV Buying Guide - Which TV Is Best For You?
Subscribe to our YouTube channel
Back
Top Bottom