Vivere DAC Settings

Hi,

can someone lease explain how the settings on the DAC work and what they do.

What is the best settings.

How do I know that the DAC is actually working.

I have connected my CDP to the DAC with an optical cable.  and then with RCA's to my amp.

I can't really note a difference between the CDP on its own and through the DAC.

What am I doing wrong here?

Thanks,

Andre