I acquired the Ruby Z a few months ago and absolutely love it. I experienced a similar issue about amonth ago. I found that in my particular instance it was due to the routing of the cables and shielding. I moved to a new house and during the setup process I must have routed my cables differently than before. I tried different phono cables and switched to different IC's between the phono pre, Aesthetix IO Sig with default loading of 47K, and the Octave Jubilee preamp, all with differing results. For instance, the rustling noise would dissappear, however, I ended up with distortion in one or both channels, like it was a drop out. It was really frustraing as I thought something may have happened to a piece of equipment during the move. On a long shot, I wrapped some polyeurethane pipe wrap around the phono cables and all was normal again.
I guess in my particular sitution, going from 220 volts to 120 and moving into an enirely new house, albeit, only temporary for now, added to the complexities. I never thought to consider the shielding of the cables to cause as many problems as it did, especially since I never had this type of issue before. It may only be a small amount of EMI/RFI leakage from a component or cable and finding the culprit will entail isolating components and cables until you find it. The cables or equipment may only need to be adjusted a few inches if it is leakage of signals. I hope this helps you, it sure helped me.
BTW, the Ruby Z is completely broken in now and sounds fantastic, very impressive and lively sounding. I will add a review shortly.
Ciao,
Audioquest4life