Hey Maxvla, this is a guts extraction of a RA-1, vaguely based off of the HPA.
The HPA-1 is close to being the same circuit, yes, but in my mind I'm paying for the direct design by Sidney Stockton Smith, Joseph Grado's selection of best ALPS pots and custom made condensers, Ultra-Wide Bandwidth cabling, and the ability to be both portable and nomad, all in this awesome casing:

And with those internals:

the amp, Joseph's version, is said to be better and less grainy than the RA-1.
And I need a HPA-1 because I'm such a filthy purist. I'm close to owning four HP1000 driven headphones now, I want the synergy people have talked (little, because little have been said about the HPA) about.
Sad part is that my only source for it is selling it for 1 000. And 900 for me because I'm a friend. He doesn't want to sell it any lower because he remember having paid 795$ for it in the days. Grr. I would like to say no to him and take more time to find one (I've already placed many ads) but he has just put the HP1 on top of it, for 2000. And no my source isn't LFF on Head-Fi, who is offering almost the same deal (but a tad cheaper). 1100 for the HP1 is great though! but he will only sell the combo (2050 with shipping). I already have a HP2 so if I could find a cheaper HPA I would go for it and leave the other combo behind, but I might also accept the combo as well, if I can't find any other HPA.

Looks so much better than a RA-1..
Edited by devouringone3 - 4/1/12 at 4:57pm