While not specifically with the Bithead I have had noise issues on the USB output if I had my laptop plugged in. This has varied from computer to computer, but might be something else to check out. The bithead I had on loan for a short while (for a Boston meet) was darn near silent in my work rig.
__________________
SB3/Arcam CD73 -> Hertsens Signature DAC -> Project Menace -> HD650 | Woody HF-1
-Head-Fi Feedback-
d-_-b
|