What Silenced the Ground Loop?

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.

By the way, there is no problem having the rcas and xlr's connected at the same time.

Have you tried disconnecting the XLR pair while keeping the RCA pair connected? I am aware they each have their own sonic signature. On my present preamp, having both connected at the same time skews the right/left balance and reduces the gain. This goes away when one or the other is disconnected. I didn't learn this until I tried it. Unless you've tried it, you also won't know if it affects your system's sound.

I'll consider trying a reversal a set of the AZ's.
Foster_9 (Threads | Answers)

So I am clear, I am not suggesting another set of AZ ICs. I'm suggesting unplugging the set you own and reversing the interconnects so the ends that were connected to the source are now connected to the Blue Circle, and vice versa.

Since the only new element in your system is the Blue Circle, I'd suggest the problem likely lies there. Perhaps try lifting the ground on the power cord that you use on the Blue Circle (by using a cheater plug).

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.

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.
Herman (System | Reviews | Threads | Answers)

That's correct. That's what I intended. Thanks for the correction. A cable's directionality has to do with the shield being connected at one end and not the other.

What's important for Foster9 is that he turn his IC around to see if the hum is eliminated by doing so. Wouldn't you agree?

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.