EMI Interference

Hi Everyone,

I posted a problem here before with a problem i had and got the solution! so thanks again to those who helped with that!

I have another problem. EMI. Has anyone experienced electromagnetinc interference problems with graphics cards? I have an EMI problem and i suspect my graphics card to be the cause.

I am a guitarist and i have two separate sound setups on my computer. one for regular audio and one for recording. The regular audio setup involves a speaker set with four speakers and a subwoofer and is connected to the motherboards sound output. I have absolutely no problems here, its all fine and sound is very good.

Where i am experienceing the problems are...
1) In my guitar amp. When i play guitar with high enough gain and distortion i noticed it picking up what sounded like digital noise.
2) Separate from my everyday audio setup i have a recording setup. This includes an Edirol FA-66 firewire audio interface. 2x Mackie MR5 active studio monitors.

Here is why i suspect it is caused by the graphics card. There is a constant EMI digital sounding noise present but anytime an image or graphic changes on the screen it changes the sound and makes it louder while the image or screen is changing.

I have disconnected the HDMI monitor cable, no change.
I have unpugged the monitor and removed the DHMI cable, no change.

When the interface is turned off the studio monitors don't pick it up, BUT even unplugging them from the sound card results in the noise going away, so the studio monitors only have the noise present when plugged into the firewire interface. They are connected with TRS balanced cables. Obviously they need to be connected but i dont think its the interface causing the problem because when the soundcard is turned off or the firewire disconnected, the noise is still picked up by my guitar amplifier but only when a guitar is plugged in, e.g. the guitar is picking it up, so its still there.

I had a wireless mouse but with that disconected and powered off its still there.

So its not caused by motherboard sound as its not present on my normal speakers, not the monitor cos its still there when thats removed, not my soundcard as far as i can tell because when thats removed the guitar amp still exhibits the symptoms, not the mouse or keyboard. I tried attaching a ferrite core to the firewire cable too but had no effect.

I'm pretty sure it must be the graphics card. I haven't ruled out the possibility of a ground loop either but it seems more likely to be gfx emi. The power connecter to the gfx is a 6pin connector and i checked to see if it had a ferrite core and it did.

The graphics card is a GIGABYTE hd5770. My brother has XFX (i think) 5770 but wont let me swap em around to see. Has anyone ever heard of or seen this kind of thing before? Its really driving me mad!

Any advice would be greatly appreciated! sorry for such a long post and i hope this is the right section. it seemed the most appropriate.
Regards,
Dean