What Silenced the Ground Loop?

I have a ground loop in my system that is audible from the speakers as the volume is turned up higher. I have a Blue Circle integrated, and one of my sources is a Raysonic CD128. I've had the Raysonic connected single ended. I purchased an inexpensive XLR interconnect just to hear the sonic difference since my Blue Circle has balanced cd inputs and the Raysonic has xlr outputs (not truly balanced).

Once I connected the xlr cables between the Blue Circle int and the Raysonic, the ground loop is gone. Total silence. I can turn the volume on the integrated all the way up and the speakers are silent.

What is it about connecting via balanced inputs on my integrated to not truly balanced outputs on the cdp that killed the ground loop? Thanks for your thoughts
All hums are not from ground loops. That you hum varies with volume suggests to me that it is not a 'ground loop' hum. Your RCA's output connections themselves may be causing a hum, or the tubes in the center two positions may be inducing a hum. Don't have that trouble with mine from either outputs though. FWIW.
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You might try using a cheater plug to "float" the ground at the AC plug(s) of both components; I'd also try leaving everything as is (with the RCAs connected per usual) and connect a wire between both units to effect a chassis ground. There is NO simple solution for ground loops, or differences in ground potential. Trial and error are the only sure curatives. Most can be solved with patience; some cannot. Happy hunting.

Thanks for the feedback.(no pun intended):)
Newbee: its not the tubes in the center position of the Raysonic since I had this hum before I got the Raysonic.

Tvad: the sihgled ended IC's I use on my sources are Acoustic Zen Matrix Ref II's and are directional. I don't have enough knowledge of the cable design to know if Robert Lee designs the Matrix Ref II's with the grounds floated or not.

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Tvad: Yes, I did have the ground loop (or whatever it is)prior to connecting my Raysonic with XLR's. Using the AZ RCA's with both of my cdps I have had the hum. In fact, I've had 3 different cdps connected up with rcas' and have had hum with all 3. The only exception has been when I connected the Raysonic up to the balanced inputs on my integrated. That config has no hum.
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No I did not have hum with the DK except when I had it connected to a particular AC regenerator I had previously. By the way, there is no problem having the rcas and xlr's connected at the same time. Each has there own sonic signature. And the xlr's are inexpensive Belden wire with Neutrik connectors(Blue Jeans), but they sound pretty darn good and aren't fully broken in yet. Thanks for the thoghts Tvad. I'll consider trying a reversal a set of the AZ's.
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Directional means the ground is floated at the load end (in other words, the ground is not soldered to the RCA outer ring at the end that connects to the preamp).

That is incorrect. A cable can be directional if there is an outer shield that is only connected at one end but you have to have the ground (outer ring) connected at both ends. It can also be directional if there is a terminating network on one end.
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Also, try disconnecting the single ended ICs from both the BC and cdp. There are some preamps and integrated amps that do not like having only one input connected and will hum until one other input is connected as well. Give it a try, see what happens.
And yes, the Blue Jeans XLRs are really good. Their single ended cables are excellent as well, although not quiet as detailed and do not do the soundstaging as well as AZ Matrix Ref II.
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Grant, no time for testing the cables today. I barely had a chance to do any listening. I will test them soon. As always, thanks for the suggestions. I will post my findings.