Possible group loop with balanced cables

Hi. I hope some one with more experience can offer some advice. I just replaced some single-ended cables with balanced. The balanced cables run from my DAC to preamp and from pre-amp to amp. The single ended cables still in the system are a digital coax from my CD to the DAC and from my TT into the preamp.

The balanced cables seem to have introduced a ground loop hum into the system. Is this likely? Is the fact that I have a mix of balanced and single-ended cables part of the problem? Any insights are appreciated.
It seems that you do not have a true Balance connection at the socket. Research "Pin 1 Problem" in Grounding scheme and you will get your answer.
Hi, I once had a hum coming from a Threshold SA10e mono amp with a balanced connection. This hum would come and go. I did a little detective work and discovered that the xlr input was loose where it connects to the amp chasis. I had to remove the top to the amp to get access to the small nuts which secure the screws on the xlr. The hum has never returned. I'm not sure what I did but my guess is that I grounded the xlr input to the amp chasis. Just wanted to pass this on.....Jess
Thanks for the helpful replies. Given this problem, it seems like there is no benefit to xlrs unless noise is a known problem. Maybe it's better to stick with well shielded unbalanced or semi balanced designs.