Postby Crunchifyable » 18 Oct 2011, 18:49
Have you tried plugging a known good patch cable through the effects loop, with the loop enabled? If you still have noise with a simple cable connecting the loop, then yes, maybe something is wrong.
If you add effects to the loop, you will probably hear a small bit of noise, which can come from cables (which aren't perfect) and the effects themselves (which can add noise).
If you know for sure that the effects device and cables you have are good and relatively noiseless, then I'd consider taking the amp back or having it repaired.
I will say that an occasional rustle sound could be RF (radio frequency) interference, which is caused by your effects devices or amp picking up radio waves. Shielding is supposed to mostly eliminated.
Sort of funny...mine has a slight, very low volume rustle sound that goes away almost completely when I use bypass the pre-amp and use the effects loop. Sort of the opposite issue, and quite minor.