I have a Massdrop Airist R2R DAC in perfect working order. It has no known issues and sounds amazing. I am asking $400 with Paypal F&F buyer pays shipping or $450 I pay shipping and Paypal Goods and Services.
I tried to do an objective test of the ifi iPurifier3 as doing a proper blind ABX listening test would require two of the same DAC.
Thought process was sort of stolen from a video made by Passion for Sound where he compared usb cables to each other by recording the DAC output with a USB audio...