ok, yes, i am opening a can of worms here, I am aware of that.

However:

I recently moved, and since then have run into problem after problem with ground loops. First off, here is my current equipment.

Samsung DLP.
Onkyo TX-SR604
5 speakers(center, right/left/surr left/right)
EuroPower EP1500 Amp pushing two 12" JL subs.
APC power backup


All this is run of a single circuit, so there shouldn't be any phase problems.

Onto the problems:
-The first problem I had was with cable TV, it had some ground loop problems, which i fixed with a Jensen VRD-1FF. That was all fine, life was great, no more humming.

-The second problem, not more than a week later, i hooked up my laptop to my system in order to play a few movies in HD. But lo and behold, the hum comes back whenever i plug my laptop into the wall to charge it.
Basically, whenever i have my laptop connected to my TV(either audio, or video) as well as the wall socket, i get obnoxious feedback, whether the amp is on or off.

The laptop is connected through VGA as well as a 3.5" connection to the TV. This then routes the audio out to the receiver, which pushes the speaker, and sends the signal to amp yadayadayada... There are no problems encountered when using my xbox or DVD player, or laptop on battery.



Now, to my question: What in gods name could be causing this?

Here is a little (attempted) explanation of the way everything is connected powerwise:

Power Backup is connected to the wall.
From that, I have the TV, receiver, xbox, and a router connected to the battery backup plugs. The surge only plugs have a DVD player, another router, a empty socket,as well as a separate surge protector(which is used as an extension cord to power the amp.

If I hook the laptop up to the battery backup, i get a really loud, but hollow hum. If I hook it up to the surge protector, it is a little quieter and fuller hum. And if i hook it up to various sockets around the room, it is loud and full.

Any idea what could be causing this? I'm sure I could bypass it with a 2->3 prong power adapter, but I would rather fix that problem than cheat around it and leave my equipment vulnerable.


Any help or comments you could give would be greatly appreciated, and if you need any clarification, don't hesitate to ask.

It is a simple ground loop from the laptop.The proof is in the fact that you can use it fine on the battery power. Even though it is on the same circuit it is giving you 2 paths to ground. Whenever we have to hook a laptop into a system we always use a Direct Box like this

http://www.proaudiosolutions.com/product-p/pcdi.htm

There are others out there as well that may be cheaper.

It is a simple ground loop from the laptop.The proof is in the fact that you can use it fine on the battery power. Even though it is on the same circuit it is giving you 2 paths to ground. Whenever we have to hook a laptop into a system we always use a Direct Box like this

http://www.proaudiosolutions.com/product-p/pcdi.htm

There are others out there as well that may be cheaper.

We've had lots of problems with computer power supplies, especially Dell. This solution that Speco pointed is about your only option.

thanks, never thought about the fact that the power supply itself could be the noise factor.

thanks, never thought about the fact that the power supply itself could be the noise factor.


Its not really the power supply, well maybe the design, but it is a ground loop. A poorly designed power supply can lead to a ground loop. Even a well done one could as well since you are providing 2 paths to ground on the AC.

It isn't really the design of the power supply as much as it is the cheapness(read efficiency) of the laptop manufacturers. They use a common ground it seems, so that the video, audio, and AC grounds are all tied together. and when that occurs, we all know the outcome.

Seems like a real hassle to go from my 3.5mm headphone jack to a box to XLR and then convert that back down to RCA or 3.5mm for my system to handle it, and all for that box to lift the ground of the audio output, and therefor the common ground of my laptop...

After all the conversions and whatnot, I'm sure there will be signal degradation, as well as a hassle of a billion and a half cables to hook up this box for something it isn't really even meant to do. In this situation, it might just be best to go to Home depot and buy the worst invention known to man: the 3->2 cheater plug.

Thanks for all the help, now its just time to see if it is worth the $200 investment to protect against the minute chance a problem will occur one of the few times my laptop is actually hooked up to the TV.

Just my luck I imagine, even went through the trouble of drilling through the wall to ensure everything was on the same circuit.

Just my luck I imagine, even went through the trouble of drilling through the wall to ensure everything was on the same circuit.


The extension cord was invented so that you don't have to do that!


How about this ground loop eliminator? Not sure why you would want to use the analog outputs out of the laptop. No DD 5.1 or DTS out of that type of connection.

http://www.radioshack.com/product/index.jsp?productId=2062214&cp=&sr=1&origkw=ground+loop&kw=ground+loop&parentPage=search

They use a common ground it seems, so that the video, audio, and AC grounds are all tied together.

This is true for just about every peice of AV equipment produced.
Ground is a common zero volt reference.

Just my luck I imagine, even went through the trouble of drilling through the wall to ensure everything was on the same circuit.

You could have used a multimeter, it doesn't require a drill.

This is true for just about every peice of AV equipment produced.
Ground is a common zero volt reference.






Most AV equipment does not use a ground. Most AV jacks are "grounded" to the DC power in the unit, and not to the 110 VAC neutral wire.

Most consumer level AV equipment does not use a ground.


Chassis ground, is a common zero volt reference point, used by both audio and video signals.

OK?