@DougofTheAbaci: At a local head-fi meet I had the WA7 connected to an ASUS Ultrabook using the ASUS power adapter and a standard, no-frills but shielded USB cable. Zero noise. None. Also using JRiver Media Center. No dropouts either. Just very clean sound.
The fellow next to me running a Mjolnir and W4S DAC-2 connected to a Macbook Pro was experiencing digital hash at approx 40~45 dB SPL below the playback. It added an edgy harshness to the sound. If there had been more setup time we might have been able to sort it out. With the proper power both are quite capable of great sound. The AC mains was not a clean source of power. Lots of computers in the room.