I'm not sure if this is the exact part number but it is similar to Digikey 240-2539-1-ND. In thinking back (I built the board in March), I'm not sure the ferrites could have anything to do with the problem since initially I did not install the ferrites, but simply wired across the pads for the ferrites. If I do hook the DAC to my computer, it plays music without a problem, but I get the hum/buzz along with the music. And I get the hum powering the DAC with a battery and nothing connected except the outputs to a headphone amp. Of course when the battery is removed, the hum goes away. It sounds like 60 Hz, but could be higher and the frequency seems to go up slightly over time. Something is oscillating, but I don't know where to look.