[jvgig]

I have a pair of Adam A7x hooked up to my computer's Asus Xonar STX with RCA cables.  Out of one speaker's tweeter, I am getting a high pitched noise, even with no input signal.  It is particularly odd because the other speaker does not do this, even when I switch the RCA L/R cables.  I then switched the left and right speaker so that the power and signal were both changed, but the same tweeter still hissed. This originally made me think something was wrong with the high frequency amp in the one speaker.  However, if I change the source to my iPhone or HK 3700AVR both speakers work flawlessly, no buzzing at all with the same source file, same cables, same power source.  In fact, going from my computer->hdmi->AVR->speakers is the only way I can play directly from my computer without buzzing.  Unfortunately, I need the AVR to power my hometheater which is in a different room.  I also tried changing the PCIe slot of the sound card in hopes of eliminating a source of electronic noise from my computer, but it did not help.  I have also tried the onboard audio and a USB Fiio E17 DAC, all resulting in the same buzzing.  The only way I can get clean audio out of my PC is with headphones, and with headphones, the Asus STX, onboard, and USB DAC all work fine.  Needless to say this is very puzzling to me and the buzzing is ruining the music.
 
Any ideas why the combination of my computer as a source and this speaker is having a problem?
 
Thanks in advance for any ideas as I'm stumped!

 

[jvgig]

I have done some more trouble shooting.  I have unplugged all fans, all extra hard drives, DVD drive, removed every PCI/PCI-E card except 1 graphics card, cycled through every RAM configuration (3 sticks, 6 slots) and unplugged every non essential USB device.  I have 2 graphics cards in my computer to run 3 monitors and have tried it with each of them in different slots.  No matter what combination of essential hardware I try, the hissing/crackling is persistent. I would almost describe it as a random set of beeps, crackles, and hissing all at once....kind of like a slurred drone noise from Star Wars on the Hoth planet...if you know that sound.   However I did notice that it only starts at about half way through the Windows boot screen and that it has some correlation to my keyboard.  If i hold down a key, the sound changes to a quick, consistent stutter from an otherwise random set of noises.  
 
Are there any BIOS settings that could affect this?  I have tried disabling all nonessential onboard components including sound, LAN, and firewire.  
 
Windows 8 and all of the hardware drivers are updated.
 
Any ideas?
 
Thanks!