Just got the HPA4 yesterday. It took all of 30 hours from the point I sent my first email inquiry to Benchmark to the point I received delivery. Amazing!
I owned the AHB2 for a short time last year, which I used with the Susvara and SR1a, so the HPA4 sounds very familiar to me. And when I heard the HPA4 at Canjam in February, I immediately realized I needed to have a Benchmark amp back in my system. All the observations I had made back when I had the AHB2 still hold with the HPA4, so it's not hard for me to articulate them even after a short period of time. Almost all my listening over these last hours has been with the Susvara:
- Detail, above all other things! Detail, separation, clarity, space, all that. It really rewards close/active/critical listening.
Relatedly -- or maybe this is part of the same point, but -- the amp draws out so much texture. The specific, sandy grit of a sustained, distorted electric guitar note makes me go, "Oh wow, so they really were doing something interesting there. Nice!" And similar kind of moments with synthesizers and electronic music, for instance.
Also, I notice ambient recording noise for the first time on a few recordings using the HPA4 and the AHB2 before it, which is kind of interesting.
Interestingly, I find that the level of detail and texture makes compressed material sound better rather than worse (which is what people usually complain about). It's like I can manage to hear and appreciate what's going on better with this amp, even when the musical bits are compressed into a bloody pulp.
- It makes the Susvara sound more forward than I'm used to. I believe this is not so much a function of soundstage size as it is one of outstanding clarity and intelligibility in its presentation.
- Tones sound so "true", up and down the spectrum, and so notably in the bass. Among other things, this makes polyphony/harmony sound especially satisfying. To my ears, this quality is fairly unique to the Benchmark amps.
Also worth noting is that the treble, despite the amp's neutrality and resolution, is always controlled sounding and unfatiguing with the Susvara.
- Imaging is as sharp as anything I've heard with the Susvara, especially when it comes to subtleties of left-to-right placement. Also, I need to use this opportunity to emphasize how much better imaging is on the Susvara compared to the Phi TC. Not sure what's up with anyone who says any different (ke ke).
- "PRaT": Somehow, this amp persuades me that this hand-wavey and semi-bogus concept possibly isn't. This was my biggest surprise when listening to the AHB2 and now the HPA4. I get a conscious sense of propulsion and drive that I wasn't necessarily even looking for.
- On dynamics: Very fast leading edges (of course). But also overall on the polite side, can't lie. This can be a plus or a minus depending on your predisposition or mood. So, counter-intuitively, simultaneously very detailed and kind of "laid back" in a way. I found this to be the case with all headphones on the AHB2, and not just with the Susvara on the HPA4.
Anyway, that's a quick enumeration of the various distinguishing characteristics I find with this amp. To call it simply the most "transparent" or "realistic" because of its low distortion is kind of simple-minded, and ultimately un-useful. It really does have its own distinctive sound signature.
Also, on other headphones: I did only a quick sanity check with the Utopia, just enough to confirm that I'll be very much looking forward to hours of quality time with that pairing into the future. And I was not taken by the Abyss Phi TC pairing. It's safe to conclude at this point that I just don't care for the TC with solid state amps in general as a matter of personal preference.
Good choice! Coincidentally I was about to get the HA-300 to pair w/ Susvara before pivoting to HPA4 last minute. I see you have both.