Ridiculously Loud White Noise Out Of DAC

[Lancerhb2]

I recently purchased a pair of KRK Rokit 5 Studio Monitors. I connected them via RCA to 3.5mm jack into my PC. They sounded great, except that they had a white noise/popping/crackling noise emitting from them that changed when I opened a program or moved my mouse. When I plugged the jack into my phone and played music from that, they worked beautifully. I did some research on the problem, and found that you needed an external DAC to fix the problem. I've purchased this DAC from amazon http/. I've connected my optical from my pc to the DAC, and RCA cables from the DAC to my KRK's. However, now I have a new problem. Whenever I play audio from my pc, the speakers emit EXTREMELY loud white noise. I've also plugged headphones into the DAC through its jack and still get white noise in my headphones. It's not the optical port on my pc because I've been using headphones with optical for about 2 years. You guys will either look at this post and majorly facepalm because of some stupid mistake I made (I'm not an audio wizard), or you'll be just as confused as I am. I also do not have much money to spend, so I need a cheap solution (not a $150 mixboard to run XLR through or something of that sort) Thank you very much for any support.

 

[americanaudiophile]

Check that you are sending 2 channel PCM to the DAC. If your PC is sending 5.1 channel audio into a 2 channel DAC you would get white noise.

 

[Lancerhb2]

Thank you so much, this fixed the white noise. However, I am still getting cracking/popping/screeching from my monitors. I know that a very faint amount of white noise out of studio monitors is normal, but this is still a large amount of noise that corresponds to actions on my pc. Do you think maybe I need a ground loop isolator?

 

[americanaudiophile]

If your monitors have 3 prong AC cords you could try a 3-2 AC adapter to break that ground. Cheaper than an audio isolation transformer.
These noises could be RF which would be harder to eliminate. You could try ferrite rings on the audio cable to the speakers (as close to the speaker as you can).