I'm looking at these two as well. I've read a couple review threads on each individual one, but am still trying to assess how they compare. I'm just looking for a portable (as in laptop/bag portable, not media player/pocket portable) to use with my MacBook Air that would be a decent upgrade from the Fiio E10, which is OK for the price, but is still a little muddled to me.
I'm particularly trying to see which one has a blacker background, is more neutral, and how the soundstages compare to each other, and/or how either compares to the E10 if anyone happens to have one of these and the E10. I've seen people mention the D7's being somewhat neutral and with good soundstage, but in a more general sense than a comparative sense.
In terms of features, from what I'm reading/seeing, the D1 doesn't appear to have a gain switch, while the D7 does. The D1 has an optical input, although that doesn't matter to me since the MacBook Air doesn't have the analog/optical combo output that the MacBook Pro has--it is purely analog on the MBA, so I'd only be using USB anyway. Looks like the D7 is a bit smaller in size, although the weight is trickier, since the AE website lists the D1's weight (~500g) as "shipping weight", so it's hard to properly compare vs the D7 (108g).
In comparing the review threads for each here, I'm seeing more people with technical issues with the AE D1--a couple people having to workout "popping" noise from power interference (I think they all managed to fix everything in the end, but it still seems overly sensitive to begin with) and a couple mentions about non-linear volume "jumps" at lower levels--but I'm just going by what I read here. Maybe someone with more experience with them knows more here...
Right now I'm using Beyer dt880 & dt990--both 250ohms. The dt990's already have more than enough color for me (although I only use them about 1/4 of the time) which is why I want something neutral. I also keep looking at the JDSLabs O2 and C421 amps, but since I don't want to get into daisy chaining separate DACs and amps in a "portable" solution, I'm not sure how much quality I'd lose running those straight from the MBA's (mid-2011) headphone port, so I'm still leaning towards another DAC/amp combo for under $200.
Edited by bluishgreen - 1/29/12 at 4:07pm