Pros: Looks great, price, seems durable, Burr-Brown PCM2702 DAC
Cons: Sound, volume, sound
Yeah, I agree with The Wuss. I am rather new to the headphone amp universe. So, don't choose to (or not to) buy baseed on my review alone.
I listening to the HiFiMAN EF2A through my Grados and a pair of Sony Studio Monitors I use for live music mixing. The Sonys were instantly revealed as crap for critical listening. The Grados came to life and quickly taught me what the term "muddy" was all about. This amp reproduces the upper lows through the lower mids as though they are on top of each other. These frequencies are fuzzy and sound as if the phones are being asked to play too loud without enough wattage, even at very low volumes. Turn them down low enough to begin to resolve this issue and you sacrifice balance. The left can is much louder.
This problem leaves you adjusting, constantly, the gain on the amp as well as the volume on the computer. Unfortunately, each song is different so the search for the proper balance goes on and on. But, every now and then, your music player shuffles you to a tune that matches the perfect recording with the correct volume levels and you get perfection! The soundstage is huge, the highs (although usually bright) pick out the vocals and strings delivering a fleeting glimpse of what you were looking for when you bought this thing. But, the lucky song ends and then it's back to back to your mixing job.
I am going to stick with it and try some new tubes to see what I can wring from this beauty. The best comparison I can make is to a super-model stereotype. Very pretty on the outside, but her personality leaves you wanting. The more time you spend with her the more frustrated you get, knowing the relationship is doomed almost from the start. But, you definately want your friends to see her before you trade her in. (Maybe one of them will want her!)