Weird speaker noise/white noise coming either from Mac Pro or Cinema Display

[Silly John Fatty]

Hello,

I noticed that some times, there's some very silent white noise coming out of the speakers of my Cinema Display (27"). This is usually when I hit the volume keys on the keyboard, then it starts. After a while it stops again. Or actually I think it happens anytime a sound is played form the Mac.

It doesn't happen when the Mac Pro's integrated speakers are selected as the output. Only when the Cinema Display is.

I don't know if this is a Cinema Display issue or a Mac Pro issue. The Mac Pro is a 5,1.
It was in repair not long ago and this issue started when it came back. I think the processor boards and the logic board. Apparently the PCIe slots were damaged.

I don't hear the noise in headphones. What I do hear in headphones however, are weird blips and artefacts. (even when there's no sound playing)
I hear these artefacts on other headphones too (but I don't hear the artefacts on all these headphones when plugged into other devices, so it isn't the headphones) but weirdly enough, I do not hear the blips and artefacts through the Cinema Display speakers.

Thanks for any tips or help!

 

[s-hatland]

I'm not sure this will help, but I was experiencing white noise in my Altec speakers a while back. What I did to minimize (not quite cure) was to separate the signal and power cables as much as possible. It was tough since all the cables going to and fro between my Pro and my monitor and my speakers were a mess, but I sorta used my surge protector as a "wall" where all of my power cables ran in front of the surge to plug in and all of my signal cables ran behind/underneath it. It may take a bit of engineering so that your audio cables aren't touching any power cables, but it's a free (minus time) option that may help with the noise.

this may also explain why you're not getting any noise from the pro's speakers or the headphones because those signal wires aren't interfering with power cables...

 

[Silly John Fatty]

That's funny, someone else suggested me the same thing to get rid of the artefacts that I get through the headphones (although I believe this is a different problem/story).

The cables I have going away from the MP are the power cable, a USB cable that goes to the display (for the sound), Mini DisplayPort, and a FireWire cable to an external drive.
What's the best solution to properly split these / protect them?

Also what's weird is that this only started when I received the Mac back. It did have the problem with the artefacts before but like I said I believe that's a different story.

 

[s-hatland]

since the problems started after the repair, it may not be something this simple. but, may as well try. firstly, maybe try a different USB cable or even a higher quality, properly sheilded one. the USB-IF create standards and have a list of compliant manufacturers (usb.org) but this may be a later resort. try running the USB cable from the computer to the monitor without it touching any other cables at all. tape it to the wall or desk (temporarily) and see if it helps. if it doesn't, you're troubles may be deeper than simply rerunning wires. i would maybe go back to where you had it repaired and tell them about the trouble you've been having.

 

[Silly John Fatty]

I don't think it has to do with that. I just ran several more tests and I believe the culprit is the Cinema Display.

The first thing is that it only happens with that Display, no other display and also no occurrence when for example headphones are set as the audio output and not the Cinema Display speakers.
But it doesn't always do it, as it seems.

I'm wondering if this might not be a sign that the "sound card" of the display is dying or something… I hope not…

Edit: Actually, those are two separate problems I noticed. The white noise coming from the Cinema Display only, and the artifacts, coming from everywhere, which is probably a cable problem (too much cable salad).