The issue I'm having is that the auto-sensing feature of the ADI-2-DAC will not switch to USB apparently because the 6000N is sending some a signal that is holding the ADI-2-DAC at the optical input.

Here's what I got from Audiolab: "When connected, it will offer a low-level signal to confirm connection (like a trigger connection) - hence his DAC thinking it is connected. This is a Play-Fi protocol, not strictly Audiolab’s setting."
...
So my question is whether the DAC could be made (through a firmware upgrade) to have some sort of input detection setting so that a signal at a level as low as what they're talking about would not be enough to prevent the DAC from switching to another input when audio is coming through the other input...

rossputin wrote:

The issue I'm having is that the auto-sensing feature of the ADI-2-DAC will not switch to USB apparently because the 6000N is sending some a signal that is holding the ADI-2-DAC at the optical input.

Here's what I got from Audiolab: "When connected, it will offer a low-level signal to confirm connection (like a trigger connection) - hence his DAC thinking it is connected. This is a Play-Fi protocol, not strictly Audiolab’s setting."
...
So my question is whether the DAC could be made (through a firmware upgrade) to have some sort of input detection setting so that a signal at a level as low as what they're talking about would not be enough to prevent the DAC from switching to another input when audio is coming through the other input...

Besides that you can switch manually -
SPDIF sends a carrier signal even if no audio is present.
This is what ADI-2 detects.

Only if you switch off your 6000N ADI-2 would select another input automatically.

Something that I don’t understand: normally ADI-2 should prioritize USB, see manual page 7.

Hi Ramses! Where ya been Man?  We missed you.

On prioritization:   I just tested it by turning on Wife's TV which is connected to my RME via TOS, and SPDIF indeed takes center stage!     My active USB input was immediately given the Boot.
(My Source select is set to Auto)

In my interpretation of Pg.20,  I think RME spells it out the Way it is!

Just sayin!

Curt

My 10minute old test result indicates SPDIF takes priority.  Kicked USB off the air immediately.

Not about being "connected" (Wife's TV is always connected)   

ACTIVE is the operative word.

So, it seems the OP has the choice of either turning OFF his Streaming device, or simply de-selecting "Auto", and choosing the desired input source easily via Remote, or Front Panel input.

TESTED:  Merely de-selecting Auto, and setting my primary source (USB) renders Wife's TV input (spdif) meaningless unless selected by me. 

Rasputin can take this to the Bank!    His troubles are over!   \ /

Ja? 

Curt

English can be a difficult language to understand, even for native English speakers. For instance, just today, this very morning I received the following:

“When I was young my father said to me: “Knowledge is power, Francis Bacon.” I understood it as “Knowledge is power, France is bacon.”

For more than a decade I wondered over the meaning of the second part and what was the surreal linkage between the two? If I said the quote to someone, “Knowledge is power, France is Bacon,” they nodded knowingly.

Or someone might say, “Knowledge is power” and I’d finish the quote “France is bacon,” and they wouldn’t look at me like I’d said something very odd, but thoughtfully agree.

I did ask a teacher what did “Knowledge is power, France is bacon” mean? And got a full ten minute explanation of the “knowledge is power” bit, but nothing on “France is bacon.”

When I prompted further explanation by saying “France is bacon?” in a questioning tone, I just got a “yes.”