I had a light hiss/hum when I first set up my 970, but once I re-did my cables and kept everything seperate it almost completly went away. I have also had issues in the past because there was a tranformer plugged into the same circuit from something such as a phone charger, printer, etc....
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Marantz SR57012,Panamax Power Conditioner, Rega P2 Turntable, Fronts - B&W 684 S3's, Center - B&W LCR600 S3, Surrounds - PSB Alpha, SVS SB4000 Sub woofer, LG 55" 4K LED Screen., SVS Speaker Cable.