z5500's to blame?

[Luca1]

Hi,

Have Xonar D2X soundcard running through 2 powered studio monitors (front of house), and bringing up the rear are the logitech z5500's (centre, left and right surround satellites and 12" sub)

When running the 2 powered studio monitors I have no dramas, but when I plug in the xonar into the 5500's control pod and run the surround setup I get crackling through all speakers.

What the possiblities? aside from the usual logitech sarcasm

Could the control pod be holding back the soundcard or system via power or increased latency?

Should I return the logitechs for replacement?

Any suggestions?

:Luca