Onboard Audio Chip Noise (cannot figure out) - diyAudio
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Old 20th September 2014, 03:39 AM   #1
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Question Onboard Audio Chip Noise (cannot figure out)

I have a Supermicro C2SEA board which sports the Realtek ALC888 (HD 7.1 channel audio).

I keep getting a computer-sounding background noise (quite lowlevel in audibility but is easily faintly noticed during pauses in sound). It sometimes happens when I move the mouse around the screen. And, it sometimes happens when the HD drive is accessing data and when the network chip (on the motherboard also) is transceiving via CAT6 a large amount of data.

Could this be an issue with an improper ground? Or, could this be an issue with the PC's power supply? Supermicro does not make bad boards.

I do know that lowlevel noise can happen in automobiles, why, and how to fix it. But, never had this before in a computer.

And, this has been the case for years (the board is from 2007 I believe). I have been using an E-MU 1820m system or ESI Waveterminal 192X card to get around the problem.

For testing, it would be cool if someone could tell me how to "shield" the PSU from the motherboard or make a tiny shield around the Realtek chip to temporarily see if that helped (Faraday cage, right?).

Thanks!
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Old 20th September 2014, 03:49 AM   #2
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I don't believe its feasible that shielding will do any good because this problem is unlikely to be due to radiated noise. There are probably a couple of issues here - common mode noise and common ground impedance coupling. Both of which are caused by interference currents flowing in ground conductors. If you could get a ground connection (for the audio output) right on the ALC888 IC you might fix up the second of these issues. The first is tougher to solve - going to a linear PSU for the computer will most likely help.
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Old 20th September 2014, 05:27 AM   #3
sangram is offline sangram  India
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This is not a problem that can be actually resolved. The only way to see of the board is the culprit or not is to replace the power supply.

The last time I encountered this issue, even that did not helps as the board's onboard filtering was inducing a massive amount of junk into the PCI slot power inlets and the power line for the onboard audio. Only replacing the board solved the issue,

It's not a question of supermicro making bad boards. It's just not intended to be used for any serious audio work, just system sounds. You're art least lucky that the pci slots are getting decent power.
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Old 20th September 2014, 05:27 AM   #4
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Thank you. I will investigate and make attempts. The ALC888 should be a pretty decent chip although I like my E-MU 1820m and WaveTerminal 192X better, heh.
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Old 23rd September 2014, 02:17 PM   #5
marce is online now marce  United Kingdom
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simultaneous switching noise is also a culprit.....
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