Building on the success of the first Rx amplifier, ALO has released a Mark-Two version of its popular Rx portable amplifier. The ALO Audio Rx Mk2 amplifier still carries mostly the same sound signature as the first. Of course every sound signature has their own fanbase, and likewise the Mk2 will continue to sound good to people who enjoyed the original Rx. One of the most impressive aspect of the Rx, that is its superb bass impact even when driving big headphones, remains a strong feature on the Mk2.
The change to a bigger sized enclosure seems to contradict the current trend of miniaturization. The first Rx had a perfect footprint to match the dimension of a typical Ipod, but the newer one is bigger and heavier. The decision to go bigger is to accommodate the bigger batteries and to match the footprint of the CypherLabs Solo transport. The change of dimension probably won’t matter as much as the added weight of the new version. With the pack in my pocket, the new amp and an Ipod feel significantly heavier than if I was carrying the original Rx. Of course, the new hairline finish anodized finishing looks much classier than the first version, so the change on that part is very much welcome. Another welcome change is the addition of a lo/hi gain switch in the front panel. As one of the few ultra-powerful portable amps in the market that can conveniently drive full-size headphones like the Sennheiser HD800 or Audez’e LCD-2, the gain switch makes it convenient to switch from using an IEM to a big fullsize. The low gain setting is noticeably more refined, has a better separation, and a blacker background than the high gain setting. So it’s important to keep the amp on low gain whenever you can. The high gain, on the other hand, is very powerful as I use it with big full size headphones like the LCD-2 and the HD800 (although don’t expect them to match a decent powered desktop).
Having mostly the same sound signature as the original Rx, the question of “is it worth upgrading?” would be asked by most of the original Rx owners. Comparing the two amplifiers, the new amp has a slightly larger soundstage, a bit more forward presentation, and a little more bass presence. Not only is there more bass quantity, but the punch is also stronger, especially when driving fullsize headphones like the LCD-2. The Mk2 is one of the punchiest portable amplifier around. The new amplifier is also slightly smoother and more refined. Both are less refined at high gain, and with sensitive IEMs like the JH16Pro, you can tell that the separation is less clean on high gain, and the signal more noisy. Of course, most amps exhibit the same “problem” on high gain setting, so it’s understandable if the Rx-es also have this issue.
The Rx has always been a superb portable amp, and the Mk2 will undoubtedly be another favorite. If you are looking for a portable amplifier, the Rx would be one of the amplifiers that I recommend. However, as with any audio gears, it would be best if you can find a local store that offers auditions to see if the signature matches your music.
Gears used for review:
Source: Hifiman HM-602, Ipod Classic
Headphones/IEMs: Audez’e LCD-2, Sennheiser HD800, HD650, JH16Pro, UM Mage