There were only two setups at the meet:
- Source Music
- MacBook Pro running OS X 10.8.5
- Audirvana Plus [hog mode and integer modes enabled]
- Objective DAC
- Objective 2 or Bakoon Audio HPA-1 amplifiers
Compared to what I'm used to with the Objective 2, the HPA-21 had more impact with the bass and just overall sounded more lively and dynamic. Instrument separation was a little better with the HPA-21 too. On the other hand, I don't know if it's the Objective 2's characteristic spacious sound or something, but the HPA-21 seemed more aggressive to my ears with a more in-your-face presentation of things. For a general overall sound signature, I like the more laid-back and relaxing presentation of the O2, but the HPA-21 definitely brought out some of the details that weren't as apparent from the O2.
The overall verdict was that the Alpha Dog is a pretty darn good headphone at $600 based on the two amps above. Daft Punk's Random Access Memories album is a great pairing with the Alpha Dog. Those rippling bass notes in Motherboard are awesome!
*These observations were with the voltage-labeled output instead of the other one labeled current and the Objective DAC were used in both setups.
I did briefly try the current output jack with the Alpha Dog and to me it lost some of the micro-details as well as having less impact with the bass.
I would have taken a photo at the meet, but I forgot my camera at home.