Since I don't believe this has been done yet, let's get a look at the uDac-2 measurements with RMAA.
First, a little background, I purchased a uDac 2 on 21/01/11 on Amazon and received it on 27/01/11 in Beijing, congrats on the fast delivery. And as I said on a previous post, the uDac-2 was a disappointment at first because of numerous audio glitches, dropouts... especially in WASAPI, but like most problems in Windows, they sometimes disappear after a restart (and sometimes reappear later). So, I did those tests in a bug free session. The test was run under Win & using the latest version of RMAA
The uDac was set at 100% volume via the windows audio device panel at 24 bit 96 kHz, studio quality, the loop in was the line in of a Macbook Pro, that is to say that the ADC is a Cirrus Logic CS4206A (AB 71), the line in was set at + 0 dB, recording at 24/96. the Headphone out of the uDac 2 was used, and the potentiometer was turned up to around 2 o'clock to get the appropriate volume.
As a reference point, the headphone out of the Macbook Pro was used, likewise volume at 100%, set at 24/96, enhancement disabled, it happens to be the appropriate volume for the line in.
The test were run at 16/44 and 24/96. I used the headphone out because it is the way I plan to use the uDac 2, it's line out may give better results (but they are still affected by the potentiometer).
A few more words before we begin, the uDac 2 is marketed as having a better potentiometer than the uDac 1 to allow better channel tracking and usability with sensitive IEMs, it turns out that the potentiometer has a huge channel imbalance at between 8 and 9 o'clock where at one point the right channel is 8 dB weaker than the left one (the point was found by using headphone and then measured with RMAA, so it may not be the max point), before 8, it's relatively balanced even if I didn't measure anything. The imbalance slowly rights itself before reaching a plateau around 10 o'clock to 2 o'clock where the left channel is 0.3 to 0.4 dB louder than the right one. Somewhere between 2 and 3 o'clock, the imbalance disappears completely, both channel are matched within 0.1 dB.
For your information, both channels of the headphone out of the Macbook Pro are matched within 0.1 dB. The issue if channel imbalance was also confirmed by ear.
Finally, please note that all the information here concerns only m uDac 2 unit, whether it is representative of all uDac 2 is a valid question. Likewise, don't consider my results as gospel since experimentation errors may have occurred.
Link to the RMAA files if you want to get a more detailed view than what is below http://www.mediafire.com/?e8pqsktlxabc8ln (PM me if the link breaks).
EDIT: Apparently, I'm not the only one to have channel imbalance issues http://www.head-fi.org/forum/thread/533779/nuforce-udac-2-hp-disappointing-using-with-hfi-780-imbalance-issue
EDIT: A replacement unit has been sent, I'll update the conclusions once I receive it.
Edited by khaos974 - 1/28/11 at 4:00pm