I have a newish iMac that I've connected to my stereo via optical out (the headphone jack doubles as such). But I recently picked up an Audioengine D1 DAC, which uses USB to bypass the Mac's internal system and sends signal to my stereo via RCA.
I'm having some trouble with the DAC as it produces a hum/buzz - a ground loop issue, I think.
While I work on a fix, I'm wondering if the DAC route is indeed superior. Doesn't sending a digital signal via optical simply use the DAC in my Cambridge Audio receiver? If so is the D1 even an upgrade?