Onboard LED's buzzing over audio devices

See if you can adjust power settings, including Cool&Quiet, to be a little less aggressive with power saving and/or monitoring.
Your board apparently can't make up its mind how much power your CPU needs, and the rapid cycling of power phases is causing your interference.

Edit: And, what PSU (brand and model, not just wattage) do you have? Your board may also be trying to compensate for an unstable power source.

There are many things that can cause 'buzzing' as such, and most of the time the root cause is a cheap or bad PSU.

If you have Utilities like Green Power II Utility installed then Uninstall. Otherwise, I see no way to control anything but the GPU Phases.

This is a LOAD issue, i.e. 9/10 a PSU issue, and as the load changes you're hearing the 'buzzing' noise. I assume the PSU is plugged into a 3-prong GROUNDED outlet; try a different outlet. Sometimes the electricians flip the phases in the sockets.

Otherwise, try the cases' speaker/mic ports or visa versa the MOBO's; verify that you're using the correct Mic port and that the sound control only lists/enables (1) Mic. Next, try the latest Realtek ALC892 drivers - http://www.realtek.com.tw/downloads/downloadsCheck.aspx...

Lastly, any sound card or USB Headset is going to be better than onboard sound.

Antec 900 Watt (80 Gold)
Adjust power in the BIOS?

Like Jaquith said, do you have any special "green" utilities loaded? Try uninstalling them, or select a high performance (rather than low power) setting.

All utilities that came with the Motherboard have been uninstalled (except the motherboard driver, of course). BIOS has been returned to its original settings (after lowering the CPU fan performance AND unplugging the fan altogether), but despite any efforts the problem persists.

This is my power supply: http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Trying a different outlet led nowhere. I do not have any soundcards.

Higher settings did not work. I enabled the Spectrum Spread and still nothing.

anyone got any other ideas?

Try moving the CPU Fan to a different Fan Header or in the BIOS if available set the CPU_FAN header (CPU FAN) to run at it's highest speed. Often the CPU's PWM (4-pin) causes a whine.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...
That is my CPU fan/heatsink.
It's a 3-pin. I tried unplugging it altogether, setting controls in the BIOS on "aggressive" and "quiet" CPU behavior, attached an extension to slow down the fan to make it quieter.

Moving fan to a different header did not work.
BIOS cannot calibrate the fan for some reason. Nonetheless, I put "aggressive" as the CPU fan behavior.
Please keep in mind that the buzzing is present even without the fan altogether.

Okay that's not it.

Q - How EXACTLY are you connecting the audio to the 'PC' and what EXACT headset?

Noticed this in the manual:
This header allows only HD audio front panel connector; AC’97 connector is not acceptable

What that means on older Case's if the Audio Front Panel isn't HD Audio compliant then it won't work properly and it's best to disconnect the Front Audio to the case.

Through Audio jacks.

Keyboard is plugged into the back jacks, speakers are connected to the keyboard (this keyboard http://www.newegg.com/Product/Product.aspx?Item=N82E168... )

These speakers are connected to the keyboard: http://www.bestbuy.com/site/Logitech+-+Z313+2.1-Channel...(3-Piece)+-+Black/Silver/9427774.p?id=1218104302605&skuId=9427774

The buzzing is heard over the speakers (which are indirectly connected to back audio jacks through the keyboard)

The other headset, which is connected to the front audio jacks, is http://www.bestbuy.com/site/Dynex%26%23153%3B+-+Earclip...

My case isn't old (brand new in fact): http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Keep in mind that on my old motherboard I had no audio problems.

Just for the record, this is my PSU http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Try taking 'the middle man' out of the equation (i.e. keyboard) and use the MOBO's rear audio:
Speakers (Green) ; right center
Mic (Pink) ; right bottom // can also try the Line In (Blue) ; right top

Yeah your older system was AC '97 compliant, this new MOBO is not.

i plugged my smaller headset into the front and back audio jacks, and the back jack has much quieter buzzing (still buzzing, but negligible).
Lemmie switch the AC '97 with the HD Audio and see what happens.

No cigar, the HD Audio has no effect on the front audio jack. Speakers, when plugged directly into the front audio jack, clearly exhibit the audio interference.

Lazy solution: The speakers' volume needs to be turned up significantly for the buzzing to be detectable. During normal operation, no interference is noticeable. As long as some sound plays through the speakers, the sound will mute the buzzing.
Regardless, when no sound is playing, the buzzing is still irritating (and it shouldn't be present in the first place anyways). But...I got some kind of backup...

Your MOBO doesn't support AC '97 - period.

Reread what I stated, "What that means on older Case's if the Audio Front Panel isn't HD Audio compliant then it won't work properly and it's best to disconnect the Front Audio to the case."

Try disconnecting the Case's audio all together from the MOBO and see what if any affects.

The case is HD Audio complaint. It has both the inputs to AC '97 and HD Audio. This is the case: http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Man you're putting your money is 'different' places, I have a $130 500R on a SB-E rig.

Again, try disconnecting the Front Panel audio all together and test. Later only use the 10 GT's HD Audio connector.

Buzz still present in back audio jack when speakers are connected directly after the removal of "HD Audio and AC 97' " cord (meaning F_AUDIO1 is unplugged)

Q - Are you using the latest Audio driver from Realtek that I posted above?

Q - Are you using the latest BIOS?
99FAD229.BST 2012-02-29 - http://www.biostar.com.tw/app/en/mb/introduction.php?S_...

Q - In the Device Manager are there any {? or !} devices listed?
Q - Did you use the latest drivers from BIOSTAR? (same link from BIOS above)

In the Device Manager, in Sound... [+] expand and Uninstall everything then reboot.

In the Realtek use the highest sampling rate (DVD); see - http://i1013.photobucket.com/albums/af254/Jaquith/SPDIF... and then change around the Microphone settings.

1. Yes
2. Yes
3. No, there aren't any ? or !
4. Yes.

I did everything you told me. Nothing changed. One interesting thing though: I tried connecting the HD Audio input into the motherboard from my old case and to my surprise the audio interference was much much lesser (when heard over the audio jack from the old case). How could my new case be providing me clearer interference than my old case?
My old case is http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Still no solution, but food for thought: when I run the AMD OverDrive Stability test, the buzzing ceases. When the stability test ends, the noise resumes.

Choices:
1. Breadboard MOBO ; Failure
2. RMA the MOBO ; choices
3. As 1st stated, any sound card or USB Headset is going to be better than onboard sound.

As I also mentioned it could be you PSU so if you have another handy then try a different PSU.

I am all out of 'magic' ideas.