As [Jan-Erik] had already built a simple USB connected Digital-to-Analog Converter (DAC), he decided to make the high-end version of it. The prototype you see in the picture above is based on ...
[joneeboi] sent in his DIY DAC mod how-to ... The audio signal is tapped directly after the DAC, and the SMD capacitors in the iPod are replaced with high end Black Gate capacitors.