Just following up with my decision to purchase a UD-10. I received one in the mail yesterday that I purchased from a dealer here on Audiogon. Unfortunately, it died after about an hour of use. This may have been my fault though, I don't know. It worked great until I plugged in the AES/EBU digital. The moment I plugged that in, it threw my DAC into a frenzy, making digital noise and lights on the front were acting weird. I immediately unplugged the digital cable, but my DAC was still going nuts, so I unplugged the power from the DAC (no power switch). Luckily after I restored power to my DAC, it came back up and works fine, but the UD-10 is now dead (at least no output from any of the digi outs anymore, the headphone out still works).
I wrote the seller on this to see how to work the warranty on this thing, but haven't heard back yet. It really sounded MUCH better than my internal card digital outs (coax) and I didn't even get to use the battery yet. So I'm curious... Is it common practice to unplug from the USB any time a digital connection is made to a USB DAC? I want to know if the device was faulty or if it's possible that its my fault for making a connection while it was powered on by the USB. The problem here is that the UD-10 didn't come with any manual whatsoever... not even a piece of paper decribing the device. There was nothing to tell me not to make any connections while it's plugged to the USB. I've done this many, many times in the past (other devices powered on when making digital connections). Actually most DAC's don't even have a power button, so they expect you to plug them in while powered on...
Anyway, it's a sad thing right now. Hopefully it's not a huge hassle to repair/return under warranty. I'll let you guys know how it goes. I will say that for the short while that I heard it, it was much better and I would buy another one if I knew it was reliable.
Ben