Well, this will all be very interesting to see pan out. I have a GTXP, a Phillips card, and the onboard Analog Devices Soundmax in various PCs, the soundmax has both toslink and coax digital outs which I can connect to the superdac. The superdac has balanced outputs...I have not yet really though about taking any measurements in RMAA, but perhaps it might be something to look into.
On to the section for those curious but less technically astute (no offense to anyone, as this includes me). This testbed PPA was built to spec right off the schematic, and I had an issue with hiss at first, which turned out to be my negligence in jumpering the bass-boost switchpads (who really needs a feedback loop anyway?). Thought I had in the back of my mind, but I had actually done the power switch pads, and my mind was telling me it was all squared away. Anyway, now that they are closed*, the hiss is gone, and DC is down to 2.1mV and 1.9mV, which is super, and there is no hiss, of course.
I'm powering it off a bastardized version of a half-PS1 type PSU that is outputting a regulated 24.4v (my on-PPA caps are 25v r-t-r).
It is a 'really nice amplifier' is what I have to offer so far. I have not had the luxury of extended listening periods as of yet, but do look forward to more time soon! It is still on the bench with the HD570s and Sony DVD player. Yeah the cans are a bit sketchy, but it's what is on my workbench. I hope to get the amp upstairs shortly to hook up to my HD580 C541i rig, which is a great workable rig, though not exotic. I'm not really the reviewing type, but the PPA is a very smooth and responsive amplifier. It initially seems very powerful, yet articulate/responsive. I have the OPA627s in it for now out of convenience, but plan to mount a few more 8610s onto Browndogs so I can load a set of them. I also have two buffers per channel at the moment (burning in for the last 20 hours now), but will populate the other six locations this weekend. I'll prolly replace the six in there now first, and repeat the burn cycle, then load all twelve buffers. I have not done any subjective testing side-by-side as of yet.
*the S2 switchpads are for the bass-boost config, which I did not want to implement on this breadboard-style PCB. You thus leave out those components, but still need to jumper the pads to enable the feedback loop to function.