PS Audio vs. Fiio D3: It was embarrassingly difficult to tell these two DACs apart.There were differences, but they were subtle and could not be identified with consistency by any panel member. The PS Audio had trouble locking onto the TOSLINK source consistently, so it was only used briefly in this one sighted pairing. Oppo HA-1 vs. Fiio D3: This pairing was also very difficult to tell apart consistently, although differences could be heard. Oppo HA-1 vs. Fiio E7: With this pairing it was fairly easy to hear a difference, and all panel members felt they could identify these DACs consistently in an A-B test. Oppo HA-1 vs. Audioengine D1: This pairing was, for me, very difficult to identify. I had compared them extensively in my own preparatory work, and when Dennis Young, Tesseract, came to my laboratory later to add his data to that from our weekend in Alabama, he also worked briefly with this pairing. His evaluation was brief, as it was at the end of other listening tests and fatigue was setting in. Dennis also had a difficult time telling the two units apart. My own assessment is that the D1 and HA-1 were virtually indistinguishable. Oppo HA-1 vs. Headroom Desktop Headphone DAC/Amp: This pairing we did not have time to work with in Alabama. I did my own A-B comparison back home, and was able to consistently tell them apart, using the final A-B test method employed during our weekend.