[Takaji]

I've been trying to figure out how to eliminate the annoying static-like hiss I'm hearing from my monitors. So far, the only solution I've found is to unplug the power supply to my laptop, which is really just a temporary fix.
 
My setup:
 
Laptop ---USB out---> DacMagic ---Balanced out XLR---> Mackie MR8 Active monitors.
 
Both monitors are plugged into the same electrical circuit as the computer. These devices are connected by grounded plugs. The DAC is connected via ungrounded two-prong wallwart transformer to another power bar that is connected to the same power bar as the monitors and computer.
 
I read in other posts that using a SPDIF connector from the computer to the DAC can help reduce ground loop problems. I tried that, and it didn't work (it only reduced a small amount of noise).
I also read about a power device that plugs into the end of any cord and then into the wall, and is said to remove any noise from a power source.
 
I'm sure that this noise is originating from my laptop, as I've plugged my LiveWires into my laptop's sound card and can hear the same thing.
 
Any ideas?

 

[beeman458]

Sounds like you need a line conditioner.
 

 

[Punnisher]

Try using an adapter plug on one of your devices to not utilize the ground pin. Either your laptop or the active monitors.
 
If the problem is a ground loop, I really doubt a line conditioner will help.

 

[Takaji]

Quote:

Try using an adapter plug on one of your devices to not utilize the ground pin. Either your laptop or the active monitors.
 
If the problem is a ground loop, I really doubt a line conditioner will help.

Not sure I can do that.. there's no way to orient the plug so that the ground pin will stick out.

 

[Ahil]

You can use a ground loop isolator, which is what i used for my home theatre. Since music is AC and the noise originates from DC current, the ground loop isolator is just a 1:1 transformer (since u cant transform DC current, only the AC current will pass through aka music only).
edit: just re-read original post and it seems ur using usb/digital out.
 
Hmm, didnt think that ground loop noise would be transmitted though digital.  I think firsty you should get a 100% confirmation of the source of the noise - Does it also happen when you run the laptop from its battery?

 

[Takaji]

Quote:

You can use a ground loop isolator, which is what i used for my home theatre. Since music is AC and the noise originates from DC current, the ground loop isolator is just a 1:1 transformer (since u cant transform DC current, only the AC current will pass through aka music only).
edit: just re-read original post and it seems ur using usb/digital out.
 
Hmm, didnt think that ground loop noise would be transmitted though digital.  I think firsty you should get a 100% confirmation of the source of the noise - Does it also happen when you run the laptop from its battery?

 I think I know what device you're talking about, but that's for RCA only, and I'm running balanced out from my DAC with XLR cables.
 
It does not happen when running the laptop from the battery. The noise is more prevalent in the left speaker. I've tested the speakers separately from the system to ensure they're not the problem.

 

[Ahil]

Since it only happens when running hte laptop from the power adaptor, then we can safely say that it is the laptop's power supply which is causing the problem.

Does the problem persist when you use a different power point for the laptop adaptor (ie. one in a sperate non-adjacent room)?

 

[Uncle Erik]

Try an isolation transformer.  (No affiliation, just a happy customer).

 

[RonaldDumsfeld]

Assuming you have worked your way backwards through your system and positively identified connecting your laptop to the mains as the culprit then take your laptop somewhere else and check if it does the same. 

 

[Takaji]

Quote:

Does the problem persist when you use a different power point for the laptop adaptor (ie. one in a sperate non-adjacent room)?

 
Quote:

Assuming you have worked your way backwards through your system and positively identified connecting your laptop to the mains as the culprit then take your laptop somewhere else and check if it does the same. 

I have tried my laptop in another room, and when using my LiveWires, I can still hear the noises. I'm convinced the Dell power adapter is total crap...
 
Quote:

Try an isolation transformer.  (No affiliation, just a happy customer).

I suppose I could try that. Are there any schematics on how to wire one up? If possible I'd like to avoid spending more money as I've spent enough on this hobby lately... but if there's no easy fix, perhaps I have no choice.

 

[Ahil]

If you have a friend with a dell laptop as well, you could try borrowing their power adaptor to see if its just your one with the problem (then again, friend's power adaptor might also have same problem). If its just your one, dell will most likely replace it for free (even if it is out of warranty, worth a shot).
 
The isolation transformer is just a scaled up version of the RCA ground loop isolators. They should also be plug n play (like the $75 model listed on the site - (TP) 12861)

 

[Takaji]

Quote:

If you have a friend with a dell laptop as well, you could try borrowing their power adaptor to see if its just your one with the problem (then again, friend's power adaptor might also have same problem). If its just your one, dell will most likely replace it for free (even if it is out of warranty, worth a shot).
 
The isolation transformer is just a scaled up version of the RCA ground loop isolators. They should also be plug n play (like the $75 model listed on the site - (TP) 12861)

 
I'll try using my friend's adaptor to see if the problem is just with mine and then get back to you.
The $75 model has 4 pins on it - am I to assume that's for two two-pronged plugs?
 
Edit: I called Dell about replacing the adaptor anyways, since I had to call about an unrelated issue with my screen. I'm still going to test out my friend's power supply in the meantime.
 

 

[Punnisher]

What I meant was an adapter plug that turns your 3 prong device into a 2 prong. It just removes the ground. Like this:
 
http://www.amazon.com/YLCT-6B-3-Prong-2-Prong-Electrical-Adapter/dp/B00166TT3G/ref=pd_bxgy_hi_img_b
 
I would spend three dollars and try this before spending hundreds on conditioners or transformers.
 
Edit: I don't know what kind of plugs you have but you can almost certainly find something similar at a local hardware store.

 

[beeman458]

FWIW, those three prong adapters are in-and-about thirty-nine cents each in our local hardware store.
 

 

[Punnisher]

All the more reason to try one. I was having ground loop issues with my mini itx pc, which is being powered by a dc powersuply (12v 4.0 amp) with a 3 pin power cord. This includes a ground pin. There was a slight hum and a buzzing when I moved the mouse. All the electrical noise from my PC was being transferred to my amplifier which was being run on the same type of power supply. I switched powersupplies to a 2 pin supply and this fixed the issue completely. I have no doubt that if I used one of these, it would have the same result.