[Omega17TheTrue]

Hello, i have electromagnetic noise from my graphic card going to my active speakers (KRK VXT6), the more the GC work the more there is strident noises going in my speakers (and different tonality).

Here a diagram :


The cable is unbalance RCA (pre-amp)>XLR(speaker) : S is the Signal, G is Ground
When i unplug the Left or Righ cable there is no more noise, strange.



Inside of pre-amp :

Red is the ground, i cut the cable at A but it really worsened the problem, should i remake the connection ?. B is a ground point of the chassis that go to next picture.



Outlet ground of pre-amp : There is resistors on the ground output, can i solder a C cable ?



What should i do ? Can i solder resistor at pre-amp input signal ground to fix the problems ?
Note : there is a button behind the speaker that lift the ground and make the noises louder.

 

[FallenAngel]

I really can't make any sense of the diagram.

 

[Omega17TheTrue]

Sorry, i just upload another version with better explanation, i understand i can seem complicated at first look.

 

[FallenAngel]

Definitely don't cut the ground (connection A), put it back.
 
How is your XLR to RCA adapter built?  You should be connecting XLR pins 1 and 3 together in the adapter to keep proper grounding.

 

[nikongod]

 
Quote:

Definitely don't cut the ground (connection A), put it back.
 
How is your XLR to RCA adapter built?  You should be connecting XLR pins 1 and 3 together in the adapter to keep proper grounding.

 
I think its an RCA-XLR adapter. It looks like the preamp is a single ended unit, and the speakers have XLR inputs. Id check the manual for the speakers to see what they say to do and then verify that it was done correctly. 

 

[Omega17TheTrue]

Its a cable with RCA on one end and XLR on the other, i don't use adapters. Since its not a DIY cable i don't know if "1" is connect to "3" but it should be since its a pro cable, how to test ?

My pre-amp is indeed single end, its a audio-gd compass.

On the manual they tell the same thing :

If you are using an unbalanced output to balanced cable conversion, make sure it is
correct. The shield is connected to the unbalanced ground of the source and pins 1 and
3 of the XLR (or the sleeve and ring on the ¼” TRS jack).

Maybe a better cable with better shielding and ferrite can fix the problem ?

 

[samsquanch]

Is your pc a laptop, if so try unplugging the power adapter from the laptop, they're notoriously noisy.
 
If your pc is a desktop, then try plugging the computer and the speakers into the same power strip, you may have a ground loop.
 
If you have a multimeter, do a resistance check between pins 1 and 3, if they're shorted, you can try removing the internal jumper, and make sure that the ground leg from your cable is attached only to pin 3.
 
Is the noise a low pitched hum?  check and make sure that there are no power cords running parallel to your interconnects.  Different signals should only touch at right angles to avoid interference.
 
What is your DAC?  does it have it's own power supply, if so, plug it in to the same power strip as your speakers.
 
What is the block labeled C on your diagram?
 
Definitely reconnect the ground wire in your preamp.

 

[samsquanch]

Also, if all else fails, Jensen makes really nice isolation transformers...

 

[nikongod]

And Edcor makes very affordable ones

 

[samsquanch]

Yeah but this is head-fi!  

 

[Omega17TheTrue]

If your pc is a desktop, then try plugging the computer and the speakers into the same power strip, you may have a ground loop.

This worked !!! I just put the PC power cable to the same power strip as the DAC/pre-amp and its remove the noise ! The other strip still have the right speaker but there is no noise (expect the normal very little idle noise on both) , so it really was a ground loop, i never thought it would be so easy to fix the problem.

The noise was really annoying, it was amplifying the graphic card strange electric noise with different sound pitch depending of the GPU activity.

Thank you very much !

 

[samsquanch]

Awesome glad it worked!  I've spent hours and even days on job sites trying to find noise in systems, it's insanely frustrating.