For a long time now I have been trying to cure the buzzing that occurs at medium-to-high volume when the amplifier is connected to my PC. This is not a hum that sounds like the typical ground loop at either 50hz or 60hz. This is an electric hissing noise with occasional clicks, and a high pitch buzz whenever I move around the mouse on the desktop. The most terrible noise comes when I launch a 3D application, such as a game. Then a loud hum appears which is very audible even when the volume knob on the amp is turned to zero; this noise only occurs when the GPU is stressed, though I can't tell if the interference radiates from the graphics card or the power supply - or both. I highly doubt it is due to the PSU since it is of high quality and power: Corsair HX1000W...
In any case, I was wondering if any of you have any ideas of how to remedy this issue. Thus far I have done the following to try and resolve the problem (mostly treating this as a ground loop):
DID NOT WORK
1. Connect all devices to the same power outlet
2. Tried higher quality + double shielded RCA interconnect from Supra, which should enhance immunity to electro-magnetic interference.
3. Muted all unused channels for the mic input (NOTE: before I started using a USB mic, I had the same irritating sound whenever I used my analog mic)
4. Chassis grounding (though I'm speculating I made errors in this part)
5. Connecting all devices to the same high quality power strip with transient filter through an ungrounded power outlet.
6. Disconnect one device at the time, in this case PC and monitor. Monitor does nothing. Disconnecting PC while turned off and RCA connected to the RCA out on sound card removes the hum (when volume on max). As soon as the PC is connected again the hum resumes, and becomes louder when PC is turned on. Same happens when connecting RCA to 3.5mm jack on mobo (onboard device). Also tried this on another PC where the buzz became significantly worse. BUT! The same thing happens with the same noise, and buzz under GPU load, when the amp is connected to the monitor (my monitor has a headphone jack + 2x USB ports).
7. (This step is mostly here to confirm it being a ground loop issue and not a faulty amp or an interference issue) While the amp is powered on for a while and connected to the PC, listen intently to the buzz/hum (very audible when GPU is stressed) and then disconnect the power cable to the amp. The amp will still be on and process sound/music until its power supply capacitors run out. All buzz instantly stopped, which confirms the ground loop occuring when more than two power connects are made to the sound system.
8. A medical grade A/C isolation transformer is generally known to be an effective way to obtain galvanic isolation/separation, but it did not work in my case.
9. Tried medium priced ground loop isolator at circa $60. This worked in eliminating the ground loop buzz but perhaps at the cost of some frequencies; which is something I want to avoid. Even the more pricey option with Jensen and Lundahl transformers will degrade the audio quality to some extent, though significantly less than a cheap transformer.
10. Another thing that worked was connecting an external DAC via optical S/PDIF. Optical is generally considered the best alternative to avoid noise from interference. Haven't tried Coaxial RCA yet.
Will a better brand/quality of RCA interconnects help prevent the amp from picking up the noise of the computer? I had planned to upgrade my current cables for the Signal Cable Analog II for better shielding and overall quality.
I also tried a fairly cheap ground loop isolator-transformator which eliminated every interference noise coming from my PC and left me with a slight white noise on maximum volume only (but at the cost of some frequencies, I fear; though not that audible.) I have considered buying the Jensen CI-2RR which is a renowned transformator of high quality which should not degrade the audio signal as other cheaper devices do. I understand computers are very noisy environments and not ideal for audio in the first place, but since I am no longer using an external D/A I have to rely on my internal sound card which I so much adore. There got to be something beside an expensive transformator that can fix this.
Edited by Monir - 11/29/12 at 9:10am