Which clock is running my system?

A S/PDIF signal combines clock, data, and various other information into a single signal. In the case of the Evo, the clock information embedded ("multiplexed") in that signal is generated internally within the Evo (assuming you are not using its external clock input). You didn't say what DAC you are using, but chances are that your DAC controls the timing of D/A conversion by using a phase locked loop to generate a clock that is synchronous to (i.e., slaved to) that embedded S/PDIF clock. That will not be the case with some DACs, however, which time D/A conversion independently of the S/PDIF clock.

All of that occurs asynchronously (i.e., with timing NOT being slaved) to the transfer of USB information between the computer and the Evo.

Regards,
-- Al

The Clock in your EVO is the Master Clock. However, there may be ASRC or asynchronous upsampling hardware inside your DAC that re-clocks the data. In that case, both EVO and DAC ASRC clocks are important. You didn't give any details about your DAC, so we can only guess.

Steve N.
Empirical Audio

The clock in the DAC controls the D/A process.

Both clocks are important, but only the one in the DAC controls the D/A process