ALO RX Mk II
I asked for and received a loan of the ALO RX Mk II from ALO audio. The amp is very low profile, but somewhat large in terms of footprint. Nice looking amp, though.
Info: http://www.aloaudio.com/store/index.php?main_page=product_info&cPath=2_60&products_id=556
Build Quality: A+ It comes in a very, very attractive metal case. There is only a very slight turn on tick. The digital volume control works quite well. The gain switch is always a very welcome thing - I used it on low gain.
Bass A+: the bass is slightly elevated in level versus the Meier Stepdance (which is my current reference in terms of neutrality, among other things). The RX Mk II has a little more bass than is strictly neutral. But it was of very good quality, and on the Beyer t50p, it was really quite welcome. Might not be ideal for already bassy headphones, though.
Midrange A: the mids were just a little lush, but were generally very clean and open sounding. The RX II lacks the supreme transparency of the top tier amps, but is verge good nonetheless. Vocals were natural sounding, as were string instruments.
Treble A: the treble was just a bit softer than on my reference amps, but was still nicely nuanced and detailed, and clean. There was a good delicacy of instruments. Brushwork was natural sounding. Here again, short of the top tier, but very good.
Neutrality A: there is a slight departure from truly neutral in that there is a bit of a downward sloping overall response. But this gives the music a powerful yet non aggressive nature that is unfailingly good sounding, and we are talking about a very subtle shading here, not a gross coloration.
Transparency A: overall the sound is grainless and clean. There is just a slightly less sense of openness versus the Meier , but taken on it's own the RX Mk II is a transparent sounding amp, with no veil detectable. This was quite obvious on well recorded female vocals, like on Alison Krauss's "Maybe", which sounded terrific.
Soundstage A: - a little deeper than it is wide, but very well defined, and puts instruments out in front somewhat, which is really nice. The image specificity was excellent, and lateral image placement was also very good.
So what we have here is an amp with no major weaknesses, and a lot of very strong performance. It's just a tiny bit fat on the bass and light on the treble, which will suit many headphones really, really well. It was a VERY synergistic pairing with the Beyer T50p. Overall I think it is a very recommendable amp, and one I'm having a hard time letting go of. If I have any issue, it's that it faces some pretty stiff competition at it's $450 price point. Still, for an excellent amp with just a bit of bass kick, if you like the footprint/size, it's a great choice.