Is it save to convert XLR to RCA?

My experience with hooking up ic's to an amp and leaving them open on the other end is a very loud and seemingly dangerous noise through the speakers.

Yes, if the RCA center pin comes in contact with, or perhaps even close to, a source of static electricity (such as your body), or anything that is at a different potential than the amp's ground. I should have thought of that when I posted.

In any event, you've established that the problem is not due to a ground loop, since it occurs when the amp is the only thing that is connected to AC power. So it would seem that the problem must be due either to EMI (electro-magnetic interference) pickup in the cabling and/or the preamp, from some nearby source of EMI, or to some defect in the input circuit of the amp. I found the Atlas manual online, and I see that it has a front panel switch to select among four possible inputs (balanced and unbalanced, direct and high-passed). I'm just speculating, but perhaps something is messed up in the switching circuit which causes the ground side of the RCA connectors to not be properly switched in.

If you haven't already, you might try switching among the various inputs, and/or unplugging the amp for a few minutes, to see if that clears out any improper states in the circuit that selects among the inputs. As the manual indicates, MAKE SURE THE AMP IS MUTED when the input selection is changed. Also, it might be worthwhile seeing if the same problem is present when you connect to the high-passed RCA input.

And if all of that leads nowhere, perhaps purchase an RCA-female to XLR-male adapter, that would allow you to try the XLR input on an experimental basis.

Beyond that, I'm pretty much out of ideas.

Best regards,
-- Al

Ok , here is what I found. With the ic's connected to the direct inputs (RCA) on the amp no matter which input I chose on the selector the buzz was there. Did not matter as long as the ic's were connected.

When I connected the ic's into the crossover RCA inputs on the amp the noise was there wether I selected the RCA or XLR inputs on the crossover inputs. But with the ic's still connected to the crossover RCA inputs and selecting the direct RCA or xlr selection on the display the buzz went away.

Ok, I have no idea what that means. But this next thing is very strange. As I changed out IC's (I use the same brand -two sets of Fusion Audio Romance and even trying a set of Radio Shack ic's) as I change them in and out and back and forth from cd player back to amp etc the buzz would change from one speaker then to both etc.... All the ic's caused a buzz, but turning off the system and placing them in different positions changed the volume and channel of the buzz. Nothing consistent in terms of each ic, but always a change.

Now I have the same 2 sets of ic's back into the system and both channels now buzz at the same level. One channel is no longer louder then the other. That is most strange and I am ready to jump on my crazy system.....

All the ic's caused a buzz, but turning off the system and placing them in different positions changed the volume and channel of the buzz.

What happens if you don't change the cabling at all, but you turn the amp off, wait a few minutes, and then turn it on, and you repeat that whole cycle a few times. Does the volume of the buzz on each channel stay the same?

With the ic's connected to the direct inputs (RCA) on the amp no matter which input I chose on the selector the buzz was there. Did not matter as long as the ic's were connected.

When I connected the ic's into the crossover RCA inputs on the amp the noise was there wether I selected the RCA or XLR inputs on the crossover inputs. But with the ic's still connected to the crossover RCA inputs and selecting the direct RCA or xlr selection on the display the buzz went away.

This increases my suspicion that something is defective in the amp's input selection circuit. That's just a guess, though.

Regards,
-- Al

It stays the same if all I do is turn off the amp and then turn back on. I may bring another speaker down to test as the problem only surfaced when a new speaker came into the system. Could it be a speaker issue? I know it is passive, but.....

Could it be a speaker issue? I know it is passive, but.....

I can't envision a way in which a passive speaker could cause the symptoms you have described. But I guess it is conceivable that a problem involving the front end of the amp, or the interconnect cables to the preamp, could be AFFECTED differently depending on whether an electrostatic speaker or a passive dynamic speaker is being used.

Regards,
-- Al