I've reviewed my share of portable headphone amplifiers, but ALO's new Rx-MK3B just might be the best on a number of counts. First, the amp is compact, just about the same size as an iPhone, but twice as thick. ALO invested two years of engineering and development time in the Rx-3B, and makes it in the U.S.
The Cypher Labs AlgoRhythm Solo is a portable digital-to-analog converter designed only for use with iPhones, iPads, and iPods, but it won't work with computers (it's not a USB DAC). There are precious few portable DACs that can accept the digital output of Apple iDevices, so it made sense to review the Rx-Mk3B and AlgoRhythm Solo together, with my iPod Classic. ALO sells a special carry bag that holds all three components, and that's how I brought the system with me on the street and NYC subway system.
The amp and DAC are designed to be used with higher-end in-ear and full-size headphones, so if you have a nice $100 set of headphones, don't even consider these; buy yourself a pair of great headphones instead.
The Rx-MK3B's connectivity suite is a little unusual; it has a 3.5mm port and balanced Kobiconn inputs and outputs (all analog connections). Right now, there aren't any portable balanced DACs, but ALO's founder, Ken Ball, expects to see them coming in the next year or two. The balanced output jack can be used with some high-end headphones from Sennheiser, Hifiman, and Audeze right now. The lithium polymer battery provides 10 to 14 hours of playing time.
The AlgoRhythm Solo digital-to-analog converter has a special USB input, a 3.5mm analog output (that goes to the Rx-MK3-B), and a RCA digital output you can connect to a home DAC. The Rx-MK3B and AlgoRhythm Solo are made in the U.S.A. The amp's metal bass and volume control knobs are machined in Portland, Ore.; they're very cool!
I started my Rx-MK3B/AlgoRhythm Solo auditions listening with a pair of $350 Sony XBA-4 in-ear headphones, and was amazed by the sonic transformation, compared with plugging them straight into my iPod Classic. The amp and DAC together made the XBA-4 sound like a much more expensive set of headphones. Bass definition was dramatically improved, and midrange and treble clarity showed strong improvement. I didn't have to jack up the volume to appreciate the differences the amp and DAC were making to the sound; it was like looking through a window after it was cleaned. Returning to the iPod on its own was a letdown; it didn't sound bad, just boring. The XBA-4 was nowhere as transparent-sounding plugged directly into the iPod Classic.
I continued listening with my Jerry Harvey JH-13 custom (molded to my ear canals) in-ear headphones. The sound was substantially more vivid and pure than it was with the Sony XBA-4s. Drums' dynamics and impact were more viscerally realistic; there was less standing in the way between my ears and the music. Quiet details, like the subtle reverberation on some of my favorite classical music albums, were easier to hear. And not-so-subtle stuff like James Brown's screams and grunts jumped out of the mixes with more power than I'm used to.
I've listened to the JH-13s for years, but they were sounding much better than I've ever heard them before. When I wasn't playing music I heard a small amount of hiss over the headphones coming from the Rx-MK3B, but the noise wasn't audible when I played music. The bass control knob doesn't add a lot of bass, but it's nice to be able to add a little extra oomph when you feel like it.
I also tried the amp and DAC with my old Sennheiser HD 580 full-size headphones, and was knocked out by the sound. Again, it was the transparency gains that made each instrument and voice stand out in bold relief that grabbed my attention. I also played the amp and DAC with the Audeze LCD-3 headphones, which sounded great, but not up to the standards of a big home headphone amp like the Hifiman EF-6 (review to come).
You can, of course, hold off on the DAC and just get the Rx-MK3B amp and see how that rocks your world. I want to stress that it's not just about playing music louder; better amps sound better at all volume levels.
The ALO/Cypher Labs stack raises the bar for battery-powered sound quality over a wide variety of headphones. The Rx-MK3B ($649) and AlgoRhythm Solo ($579) are sold direct on the ALO Web site with a 30 day money-back guarantee, so you can hear for yourself how they can transform the sound of your headphones. ALO makes a few different portable amps, and its National amp sells for $299. Warranties run one year, and after that ALO will provide service or a heavily discounted price on a replacement unit. ALO has been in business for six years.