Here is a marathon review of the HA-1 by Nicolas Bécuwe of HDFever on July 10, 2014. No doubt this is the most diverse technically/image laden review you will have the pleasure of viewing.
Very interesting indeed. Although they missed the one detail I wanted to know which was the type of opamp used. They mentioned they exist for all of the outputs, but despite mentioning very specifically the components used elsewhere like brands of capacitors and transistors...they didn't mention this which was a very odd omission.