I heard some slight noise from OPO's headphone out with Westone ES3Xs, Neutron app and quiet piano music. I called the noise "slight" as it cannot be heard while loud/busy music is playing, nor from dynamic earphones (VSonic GR07). If you are not listening for noise using really sensitive BA IEMs, you probably won't hear it. However, OPO's noise level does seem higher than my Sansa Clip+ or iPhone 3GS. OPO's output volume is louder though.
8/8/14 at 2:13pm