Hi. Thanks for the interest in our products. We have redesigned the digital output board of the D1 transport, the connecting cable, now called HD-Link, and digital input board of our C1 DAC. The latest available chipsets on these boards provide us with new processing power allowing us to implement a new upsampling algorithm used on discs played on the D1, USB, and ethernet streaming. The benefit is clearly and easily audible. Owners can easily upgrade as these boards are field replaceable. The board(s) in the C1/D1 are replaced, new HD-Link cable replaces the original, software is upgraded and the owner is good to go. We have not changed the model number of the C1 or D1. Have a look at our web-site for more information: ch-precision.com. Alternatively you can contact me at email listed below and I will get you in touch with one of our dealers.