Overall, I think this is a bit of an upgrade in sound from my NuForce Icon uDAC-2, which seemed to have a bad pot or something on the volume, and would need to be reset on occasion because it'd just stop working. Also, the uDAC seemed to have bad left/right balance issues sometimes.
It is still working fine, but, for the price, I kind of wish I had bought something with more driving power and specifically meant to sit on a desk, as I use this on the desktop at work.
Cons:
Volume control. It is nearly impossible to use without moving the amp all over the desk. I never know which way is volume up or down because of poor labeling.
Jack: The headphone jack and usb jack don't seem to be mounted quite right - the USB cord angles up. The headphone adapter sort of angles up and to the right as well.
Occasionally needs to be unplugged, or gets weird artifacts. I'm not sure what this is about.
Seems alright enough at driving my Audiotechnica ATH-M40fs headphones, but I doubt it could drive anything much more demanding.
SagaciousBYou might have gotten a bad unit. Mines drives the Sennheiser HD 660 s and the HD 650s just fine. I also haven't had any of the issues you described.