I have tried that, yet again, and can hear nothing whatsoever in terms of noise. I've tried both USB and Toslink inputs, powered and on battery. I've used ThieAudio V16 as my reference IEM - 112dB sensitivity, 18ohm impedance. I have Sparkos SS3602s installed, ESS DAC at present (awaiting an AKM module). In Eco mode with music playing, there's nothing audible, but I can still hear music in Normal or Turbo modes when the volume is on 0. I've tried dialling the volume all the way to 99 in both modes and can still hear no background noise. I acknowledge my hearing isn't as sensitive as some here, so I'm not sure what to suggest to resolve your issues.