Th sonly time I have encountered any noise was with the CSLS partnered with Halcro power amps AND with the mute switch on. The owner of the Halcro contacted Israel who i understand was aware of this on happening on rare occasions and has made changes to newer models. It was no big deal for me because it was totally silent with the mute "off" mso it wouldn't be a problem using it.
Apart from the Soulutiion 710, have also hooked up the CSLS to a pair of Gryphon Colosseum monoblocks, Jungson JA-100's , Bakoon amps, Doge 9's, mingda and McCormack power amps and one or two others with absolute silence at all times and being fed by DAC's CD players and phono stages.
I think Brownsfan's advice is right on the money - its worth talking to Israel to help solve the problem although new owners shouldn't have this issue in future.