Received the kit on Saturday and had it built four hours later. I've been listening and doing initial break-in for the last day or two.
Initial impressions are extremely positive. Really love the way this amp sounds with every headphone I own. The soundstage seems to be quite large and airy with this amplifier. With my other gear there seems to be a "gap" in the middle making imaging seem unnatural. With this amp though, imaging is more seamless and really helps place you in the performance. Another positive difference I've noticed is with bass and kick-drum. Huge bass transients are no match for this amp. I've never heard the kick drum sound so punchy and pronounced.
The impedance switch seems to do well with under 200ohm on low and over 200ohm on high. That's my initial impression anyway with the varying impedances I've tried. My dt880 250ohm really sings on the high impedance setting with a flat yet full-bodied sound throughout all frequencies. The same can be said for my 120ohm k601 on the low impedance setting. Headphones that fall in the middle between 120 and 250 ohm could go either way. It's a great feature for a headphone collector who can't be tied down to one impedance range.
There's only a couple issues I have found with my amp, and these are very very minor.
1. A tiny bit of hum is audible for me during silence. It mostly shows up with very sensitive headphones (Grado) or headphones that are middle-of-the-road impedance on the high setting (dt880 250ohm). It should be noted that I have not tried the numerous tweaks available and that I have an older house which does not have grounds on any of its outlets. Once I attach the amp to a properly grounded outlet the hum may disappear completely. Combined with the tweaks, I am confident I can get the amp to be dead silent. With that said, it doesn't take away from enjoyment at all and should not be a deterrent from buying this awesome kit.
2. I only found 3 short black screws in my kit. It would be useful to have 6 short screws for the standoff mounting. I ended up stacking washers with the long screws inside the amp which gets very close to the output transformer leads. I'll be shortening those screws and reinstalling them soon.
Thanks to everyone involved with designing and distributing this kit. It's absolutely fantastic.
Edited by Punnisher - 8/26/13 at 10:00am