Possible ground loop problem?

powermadcoop

Standard Member
Hi, I'm pretty new to this so apologies if I'm in the wrong place.

I have a tv, surround system and laptop.

I currently have the laptop video sent using s video (no VGA input on tv) and the audio sent by a 3.5mm to RCA to the aux on the surround.

Now here is the problem, if I plug in the video phono from the surround in to the tv or if I have the tv sound RCA out plugged in to the surround (I have the auc input on the surround split in to two) I get a horrible hum with lots of hard disk working type noises. I get this whether both the video and phono are plugged in to the tv or just one of them. So at the minute it's a matter of just having one plugged in either the laptop or the tv in to the surround.

I'd like a solution to be able to have both plugged in and there be no strange noises. The noise does disapeer when the laptop charger is unplugged but my laptop doesn't charge so always has to be plugged in.

Any help is greatly appreciated!!
 

Naqi

Member
Sounds like a ground loop issue, although the hard disk noise is a bit strange and not some thing I've heard before. I've had this issue a couple of times, an cheap ground loop isolator of eBay has solved it every time
 

Mark.Yudkin

Distinguished Member
The problem is fairly common. The usual solution is the one you can't use - don't plug in the laptop. The other one is to use optical connectivity from the laptop (most, but not all laptops offer this), but since you also have the issue using S-video, this might not be sufficient.

If it were only the phono, and the two usual solutions couldn't be used, I'd say use one of these between the laptop and the amp.

If I've understood you correctly, you have the TV connected to the amp using analogue phono conenctions. If tis is correct, What would likely work in your case is using the above ground loop isolator between the TV and the amp, with the laptop connected only to the TV.

This will fail if you have the TV and amp connected to some common device such as a DVD player of HDD recorder. In such as case you will additionally need to isolate the S-Video, which you can do using one of these or these in addition to the audio isolator above. Given the price, you may find it cheaper to replace the laptop's battery with a new one that recharges.
 

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