I had a crackle in my system after I added a Rotel DAC and I finally narrowed it down to the digital interconnect. Some brands may not be compatible with all players or it may be defective. I put in a different brand cable and it fixed it right away. Also, check to be sure your cables are not in a "birds-nest" behind your cabinet. Piles of cables not run cleanly and neatly can lead to noise in more complex systems. But try the first posts recommendation first because it is most common fix (using non-grounded cheater plug).
Hum in the system
Hi, I just installed a MSB Link DAC III in my system and that promptly caused a low but audible hum. The hum goes away as soon as I turn off my power amp. (but that's not exactly a workable solution....) Now, both the power amp (Acurus A-100) and the MSB have 3-pronged plugs, so I wonder if there is a ground loop problem. My question is, how do I fix it? The Mondial M.A.G.I.C won't work, because it is a cable ground isolator - at any rate I don't have cable TV. Any suggestions/solutions will be much appreciated. Thanks!