Every source I have seen says there were 2 built. One blue one that has been demo'd at NAMM and a guy from HC had it on loan for his own demos (although he claims there are 3 in existence). The other was black. At the NAMM show it was the one opened up for the gut shots next to the blue one. Looks like the black one went through 3 guys here on RT haha. I'm the current owner of the black one (assuming there's only 1 black one anyway
love, Love, LOVE this amp. Currently I'm running Chinese pre's and =C= EL34. When it's time to retube in a month or so I'm going to switch to Sovtek 6L6wxt+ and a select set of pre's. I almost traded it for a 101b, but after that fell through I decided that I'm just going to keep the thing. I also got in contact with Martin Kidd, and he has confirmed that it is the same amp as his Cornford MK50H II, but without the secondary effects loop. He said there may be a couple component changes, but he said he'd gladly give me the rundown on what I would need to change if I want to get it up to Cornford spec.
Can't speak on how it compares to a Cornford since I have not played one much less heard one in person, but I would believe the Earhart would sound the same, based on what Martin has told me.