This will be a short review, professional reviews are out there. The next of this is that if you don't want to shell out the cash for an LCD-2 but want to get the next closest thing in  the Audeze line this is it. I've lived with these now for over 3 months and they give my Magnepan 1.7's serious competition for which will be listened to in the evening. These easily beat out the Hifiman HE-400, Grado SR-225 with a natural highly detailed sound. I chose the model without the in line iPhone DAC, as it wasn't important to me, haven't regretted that in using it with iPhone and iPad. One of the really nice things is how natural the sound is, there are no surprise fails in any area. The only people who might not like this headphone are those accustomed to playing at 100 db to hear details... there is no fake punchiness in these phones that you can stimulate by playing louder.

Microzotl 2 Review
 
The Microzotl 2  is an updated version of the original Microzotl, created by David Berning over a decade ago. Berning amps do not use heavy transformers, rely on a unique RF
scheme for signal amplification. This newer version is manufactured and sold under license by Linear Tube Audio ( http://www.lineartubeaudio.com/#home ). It uses a complement of
(2) 12AT7 and (2) 6SN7GTB tubes , the stock tubes are sourced from Tungsol. Two switch selectable inputs are supported, pre amp out, and speaker connections for high efficiency
speakers that can be driven with 1 watt. A peculiarity of the design is that you should avoid having both pre out and headphones connected at same time as this may drive both outputs
in parallel, causing a reduction in power to the headphones. The retail price is $1100.

The Microzotl is special for  its price point. If you have tube equipment, chances are you love it for its mid-range soulfulness but have a closet of tubes you have experimented with trying to get the most out of it. Seems transformers, big capacitors, and tubes all interact with varying success in audio transparency as you go up and down the audible spectrum. Tube amps are often characterized as slow
on transients and compressed sounding compared to solid state gear. Pre amp tubes in a traditional tube amp can have wide variations in how each affects mid range sound. The Microzotl 2 doesn't
use big caps and transformers so those interactions are reduced..
 
Speed and freedom from distortion are the hallmarks of the Microzotl 2; listen to it on loud passages and you become aware of how other tube amps  blenderize instruments and collapse dynamics. And if you are used to a traditional tube amplifier you may at first question if you like this amp... its not the warm wool sweater of sound you are used to.  It is the sound of a tube amplifier but its one where the  mid range is fast,  no added coloration, almost a paradox. This is a wonderful match for moderately efficient orthodynamics in the Hifiman  and Audeze lines as these headphones introduce very little harmonic distortion, love this with the Hifiman HE-400 I own and  when auditioned with the Audeze LCD-2's. With a dynamic headphone like Grado SR-225 I found the harmonic distortion of the headphone driver canceled out a lot of the musical enjoyment, just couldn't hear all the amp was capable of doing.
 
And unlike the Music hall 25.2 and ifi Micro  headphone amps I own with pre out, the Microzotl2 can be taken seriously as a pre amp solution; sounds wonderful feeding Magnepan 1.7 speakers. It does show its heritage at that point as a headphone amp; big bass drum slaps you but doesn't pound you in the chest.
 
There is a good thread on this amp if interested; I make no claims that this amp is the right choice for everyone. But if like me you gravitate to planars, electrostatics and orthodynamic speaker
solutions, you owe yourself a listen to this amp.  Hopefully posting this will get more head fi-ers to give it a listen
 
http://www.head-fi.org/t/771234/microzotl2-tube-headphone-amp-and-preamp-a-breakthrough-device

I think there are quite a few reviews on this headphone amp so I see no need to do another long winded one. Consider this rather some
observations on what is a fine product but does have its quirks.
 
First my setup is typically UPNP streamed music out to asynch USB/ DAC. For headphones I currently use Hifiman HE-400 and Grado SR-225,
For comparison headphone amps I have Hifiman EF-5 and Musical Hall 25.2.
 
Ergonomics:  one has to be careful to check all switches if the amp is moved as its easy to accidentally brush one on the bottom and change settings... this happens
often with the IEM button
 
Asynch USB section: this is quite good and used in my main system marginally better than the Gustard U12
 
Amp section: excellent detail, balance and range. However compared to the tube desktop amps the Micro lacks solidity for tone colors.  They in turn aren't
quite as delicate in detail and are less forgiving of bad source.
 
DAC section: works quite well feeding my other headphone amps. However in main system compared to Metrum Octave the Micro DAC section sounded thin,
not as good as the DAC section on an Oppo 103. This seems to be the weakest part of the amp.

If you are looking for an inexpensive USB cable, this is an OK way to spend your money. It will reduce some of the digital irritants and sounds better than the "comes with" usb
cables packaged with your gear. But I highly recommend  spending the money for their next model up. The $60 spend on the better 0.5m pure silver stranded Pangea USB cable will pay off in gobs
of uncovered music detail that other USB cables in the $100 range obscure.

Although I've only had this about a week, I've decided to post since there is a dearth of posted reviews.
First about me;
prior gear I have had - Grado Headphone amp, Headroom Micro amp, Stax SR-5 headphones, Grado 325 headphones
current gear -Music Hall 25.2 headphone amp, Grado 80 headphones, Hifiman HE-400 headphones
biases - tube gear, planar and electrostatic speakers.... headphones used when I feel too lazy to fire up the main system.
Audiophile purchaser since the 80's
 
Packaging when received was plain cardboard box with foam cut outs to house the product, no issues there with
shipping protection. The 12AU7 tube provided was a generic Chinese tube which I promptly put back in the box along
with the generic IEC cable. IMHO using these stock components is basically wasting the money you spent for a better amp.
IEC used was 1M PS Audio Jewel power cable. Out of the box I started with an RCA clear top 12AU7, more or less a pleasant
fail safe starting 12AU7 for all tube gear.
 
On initial play the amp presented good characteristics but  was a bit aggressive and overly dynamic. So after 30 minutes of sampling
I put JRMC on repeat play to break in the amp. After 24 hours of play time things seemed to settle in so I began to do more serious listening.
 
12AU7 Tube rolling- I have Golden Lion, Siemens, Funkwerk, Prima Luna , Telefunken (ribbed), Mullard CV4003, RCA clear top, Electro Harmonix
The Telefunkens as always are the cleanest sounding but expose a bit of an aggressive edge in the highs. The Mullard CV4003's damped
that edge at the loss of some finer detail.  I spent the majority of time listening using the Mullards but will report back if further break in eliminates
the edge with the Telefunken or I find a better matching tube.
 
Listening musts: like most tube gear the amp required full warm up for best performance. I found that 1 hour was best to get to maximum background
detail clarity. Cable performance differences also mirrored my main system so this hopefully means that if you have cables you already like, they will
work well also with the EF-5 and not cause a frenzy of new cable auditions.
 
The sound: the best acronym to use describing the EF-5 is "pleasing". It has tube mid range, clarity, along with solid state bite, and power.
With the HE-400's I typically listened at around 1o'clock on the volume knob, and did not have to  use the +10db dip switches on the bottom
of the unit. The Grado SR80's sounded nice also with the amp but sounded like the cheaper headphones they are, stressed by the demand of the additional
detail presented. This suggests that you want headphones with good power handling capabilities, lesser headphones with good source won't be pretty.
 
Comparison: compared to the 2 headphone amps I have had and the Music Hall I still have, this is a clear winner. The Grado comes closest for midrange magic
but the battery powered version had no oomph, couldn't convince on transients. I wasn't happy with the Music Hall or the Headroom Micro headphone amp but have no desire to bash them.
 
Areas for improvement: there are basically 2 things (1) the volume knob is very stiff and the position indicator hard to see. A dot of white paint would be nice and perhaps some tension reduction for easier turning (2)  low volume detail playback seems slightly compromised. My gut suspicion is that the OPA275 is the cause. I'd love it if HifiMan worked with Dexxa on a discrete op amp alternative that could work with their case fit limitation.