Received the well packaged PORTA CORDA MkIII-USB in the mail from Germany yesterday. Finally used it this morning both as a DAC and an Amp with my iMac and then as a portable AMP with the iPod. Absolutely Breathtaking sound. The only hiss was from poor source material such as the Edith Piaf CD that has been kicked around for a while.
I can not review this device. Not qualified. This is my only experience. I just like to listen to music and the MkIII-USB makes it sound a whole lot better and I mean it big time.