Here is a DAC 4.1 Signature build that was done for a local customer.  This one got all the goodies –  triple c-core output transformers with balanced/unbalanced outputs, all Audio Note tantalum resistors on the line board (and the complete audio path), Mundorf Silver/Oil coupling caps, and the USB option.  The 4.1 is a true giant-killer.  It’s our top-of-the-line DAC, and it has a sublime sound – accurate, detailed, and pleasant.