The background on this amp is here: http://www.amb.org/audio/ck2/ and the construction thread is here: http://headwize.com/ubb/showpage.php...d=6605&fpage=1 On a whim, I had MisterX build one for me. I think there are a few others here that have built one, but haven't seen any press on it. Well, just opened the box up a few hours ago, took a few pics and then plugged her in. I'm in a transitional state with my cans right now so, the HD600s are all I have to test it with. I'm throwing different SACD discs at it now, and I am very pleased. Deep, tight bass, forceful mids and silky highs are the first impressions. They seem to have a good synergy with the Sennheisers. As it burns in, I'll post further impressions.