For reasons given in another post (Is the CD player dead?) I've got an Arcan Delta 5 Black Box Dac. I bought this off eBay without a manual. It sounds OK for my testing purposes but it has a "Sync" button on it, that when activated turns the musc into a horrible white noise hiss. Can anyone tell me what this button does or what it's for? There also has a button labelled "Phase". I'm less interested in this one... and think I know what it does... but why does it do it.. what is it useful for?