I got the Fethead today. I placed both NT1-A's in as close to the same
position as possible. I ran one through the Fethead, and the other
straight though into the preamps of my M-Audio Fast Track Ultra. I set
the non-Fethead gain to 100%, then set the gain of the Fethead mic to
match the best I could trying different sound sources and pink noise far
and close to the mics. Eventually I was satisfied that the meters were
responding identically.
Next, I traded the mics for two 150 Ohm dummy mics. The Fethead
produced audibly more noise. I applied same-gain normalization
to the two tracks, and here is the result, with the Fethead mic
on the bottom.
https://imgur.com/a/UwdLoII
So, it goes back. I could see it being handy with a portable
recorder that had horribly noisy preamps.
Toby