Before changing amps try this:
I contacted Bob at NuFORCE Tech Support and he said to try the following:
John,
He should connect the ground on the amp to the earth/safety ground of the AC outlet. This should be done for safety's sake, let alone any noise issues. With all of the internal HF switching going on inside the amp chassis (particularly the SMPS power supply), if that energy has nowhere to go (i.e., "ground") it is likely to get into the signal path and be amplified as hiss. Grounding may not completely get rid of it, but it should help.
Furthermore, once the amp has been properly earth grounded, then the customer can "lift" the AC power ground on the rest of the equipment. At that point all other components in the system will be connected to earth/safety ground through their various interconnect cables and on through the MCA's power cord to earth ground. That is called "end of chain" grounding and should help to reduce any noise even further - not to mention eliminate any ground-loops.
Although, in his case he says he doesn't have an earth ground available at all. So... if he could just get the MCA grounded, then there would be nothing else for him to do with regards to the other equipment as apparently... they already have no earth ground connection to begin with.
Thanks,
-Bob
The above would explain why a couple have mentioned a hiss, and others have none.
The Marantz used earlier was likely not of the same amp topology, and thus might not be as susceptible to a lack of grounding. And since this has only been reported in 2 incidents (but over 3 total amps) it is possible that it is a manufacturing defect in those particular samples, as all the others I have placed in the field have not needed to be grounded, and have no hiss.
Hope that helps.
