Need Help identifying / Correcting PC Audio Hiss

[bluesman]

First you diagnose, then you treat. The results of a few simple maneuvers will help you localize the source.  For example:

• Review your computer audio settings.  Are they all set as you thought they were?
• Are you using any filters, DSP / EQ etc? If so, does bypassing them all affect the hiss? If so, add one by one to find the culprit.
• Switch your gain control from hardware to software or vice versa (depending on how it's set up now) - did that change the hiss?
  • If you have multiple possible gain control points, try each one with fixed gain at the others to see if it makes a difference.
• Does the level of the hiss change with your gain control setting or is it constant at all volume settings?
• Do you hear it when you listen with headphones through the mobo audio output jack (i.e. using the onboard DAC)?
• Is it the same in both channels or is it clearly louder on one?  If louder on one, does it move when you swap inputs to the amp?
• Do you hear it when playing from your DAP through the amplifier?

Each of these and other interventions you can figure out for yourself will help you locate the offending component.  If the hiss comes out of your motherboard's audio jack too, it's obviously in the computer somewhere (whether associated with software, component failure, power noise, etc).  If not, it's in a peripheral.  If it's in the computer itself, it could be a software setting or glitch, a hardware problem, a power problem, etc. Isolate the point at which the hiss is gone by bypassing or eliminating components one at a time, moving backwards from the speakers / phones to the source.