The age of good battery life, massive power, and freaking amazing gain control is upon us. It’s the age of the ALO Rx MKIII-B+, an age that cooks your beans without over-cooking them, you know what I mean?
Frequency response (balanced & unbalanced): 5Hz-80kHz ±1dB
Gain lo/med/hi: -3dB, +3dB and +12dB
Balanced RMS output power (both channels): 640mW into 32Ω, 630 into 50, 150 into 300 and 80mW into 600Ω
Unbalanced: 320mW into 32Ω, 220 into 50, 40 into 300 and 20mW into 600Ω
Bass adjustment at max: +3.5dB@<40Hz, 3dB@80Hz, 2dB@160Hz, 1dB@260Hz, 0.5dB@360Hz and <0.5dB@>360Hz
<1 Ω Output Impedance
Built in Rechargeable Lithium-Polymer Battery
Playtime: 19-24 hours
Recharge Time: 3 hours
Charges via included wall power adapter
Made in USA
ALO Rx MKIII -B+ 649$ USD
ohmage & porridge: haptics
On the outside, little beside the font stencilling technology has changed. Still the inputs queue across the back. Still the outputs queue across the front. Still a twist of the volume pot powers the amp up and powers it down again. Still a twist of the bass knob amps the lows. Because ins and outs occupy different sides of the amp, cables protrude from both ends; pocket use is all but precluded. Because inputs and outputs line opposite sides of the amp, you can use the fattest of fat pipe in/out connectors. Not a one interferes with gain, volume, or bass functionality. And that understated lamp? Still there, still making good bedside rigs possible. Still shining as you and your beans bump and grind to Manilow or Denver.
ohmage: kitsch and quality
Aside from the original Rx amp, which somewhat bristled with fiddly switches, the Rx series has always been solidly built. Proven construction - plate-braced ports, thick chassis, good use of steel fastening hardware - makes it possible. Seams are tight and knobs aligned with ruler-straight precision. You will find no excess dust or residue from final finishing processes. You will find no hair sandblasted to your amp. ALO take pride in their work. The Rx MKIII-B+, like all modern ALO amps, is brilliant.
The only niggle I have is the logo’s new paint job, whose dried-out-tongue-papillae feel gives me the fuzzy bunnies every time I run my prints over its surface. But I don’t do a lot of rubbing. That is, not without Manilow.
One thing that Rx owners have mildly complained about since the very beginning is background noise. Simply put, as a series, Rx amps output more shhhhhhh than is necessary. For the most part, that noise fades to the background whilst music breaks into the amplifier circuit. Over the years I have gotten along quite well with it. But I won't snub improvement. The Rx MKIII-B+ certainly improves on the B. Hiss is both quieter than in previous Rx amplifiers, and smoother. It exhibits no dips, no troughs, no peaks, no scratches. And despite that hiss still being clearly audible hiss it really does melt before the music.
The new gain system is phenomenal. Let me say that again, this time with quotable bits.
Into either single-ended or balanced ports, highly sensitive earphones are able to achieve perfect L/R balance at low volume levels. The previous Rx MKIII-B did what every Rx amp did, output flawless resolution into any earphone or headphone. But it also output too much volume at the lowest left-right balanced volume levels. Eardrums bled. It also had less than a 10% margin of error between its on state and a volume level which was too loud for pairing with sensitive IEMs. B+ allows around a quarter turn of the volume pot before driving your eardrums bonkers. Whatever mileage you cover, these sensitive ears are thrilled.
The benefits of control would be for naught if output power dropped across the board. It does not. The B+ retains the same power that its predecessor boasted. That is, it exhibits incredible top to bottom control at every current and voltage requirement. It is one of a baby's handful of portable amps that effortlessly powers both earphones as well as it does voltage-hungry planar magnetic headphones. Output impedance of less than 1Ω along with the current necessary to sustain high-resolution images really is key.
But B+ takes the Rx series to a couple of new places. It is the first of the series to round the spatial image into a mild parabola. The parabolic bulge is parsed thusly: a mild directrix rather directing the midrange, highs and lows fluttering at the sides and back. Top and bottom tails curl away to infinity on either side. The net effect is a greater 3D image than ever before. Similarly, contrast between mids and spectral extremities is starker than in earlier models. Is it a funner sound? Maybe. It is a softer, more subtle sound; a sound I realise now that I have long longed for.
Okay, damn it, the B+ is the funnest Rx yet. Its bass enhancement of ~5dB is subtle and less prone to bloom at high and mid-bass frequencies. Subtlety and fun. It's a wry combination upon which the Rx perches, looking down on the competition, like the Triad Audio L3, that is too big for its own good, or the VorzAMPduo, whose bass enhancement switch is far too much of a good thing. Subtle as the new Rx may be, speed remains top, and that famous resolution is as crisp as ever it was.
I have no hesitation in recommending the Rx for any earphone or headphone setup out there. Performance is still Rx hardcore. But it is the B+'s refinement of the Rx image that endears it. It retains the signature Rx detail, stage width, and power, but reins in the bits that weren’t perfect. There is precious little else ALO Audio could do to further impress me. My beans thoroughly have been cooked.