More and more, ALO is becoming a big name in the world of headphone amplification. I had my doubts when a company that specializes in developing cables suddenly turns their attention to making amps, but as it turned out, the original Rx amplifier was received very well by the headphone community. The Rx evolved to the Mk2, and in the mean time ALO also developed a different line up that we now know as the Continental and the National.
ALO’s Rx line of amplifiers have always been very powerful amps. When the original Rx amplifier was released, we found it to be the only portable amplifier able to drive the original Hifiman HE-5 orthodynamic headphone. When we tested out the original Rx along with some other amplifiers, we were surprised as the Rx handily beats other powerful amps like the TTVJ Slim, RSA’s SR-71A, and even the first generation Triad Audio Lisa III amplifier as none of these could drive the HE-5 to moderate loudness without distortions. The original Rx evolved to the Mk2 version, and finally now we have the Mk3 version that comes in a fully balanced configuration.
The balanced configuration in the Mk3-B yields very powerful results, and the Mk3-B not only drives both the Hifiman HE-500 and HE-6 better than RSA’s SR-71B and Ibasso’s PB-2 portable amps (both balanced models), or Triad Audio’s gigantic L3 amplifier, but also better than a lot of mid-fi desktop amplifiers, and better than most high-end tube desktop amplifiers. It still doesn’t kick like a good speaker amp with the HE-6, but it’s really a good combination and one of the best amps that I’ve heard the HE-6 with.
I admit that I’m a big proponent of bigger is better, and so I’ve always been a big fan of humongous sized desktop amplifiers. How the Mk3-B is able to drive the HE-6 with very good results, frankly speaking, still puzzles me. I’ve always told people that the HE-6 is best used with true speaker amps, because the reality is that the HE-6 is the hardest headphone to drive today, exceeding even the speaker-like AKG K1000. So I talked to the guys at ALO about how they were able to do this. They mentioned the use of the same op-amps as on the Mk2 and Mk1, but in bigger quantities. Other than that, the input and output sections are different than on the Mk2 and Mk1.
Like all the other balanced portable amps I’ve reviewed, the Mk3-B does suffer from the same shortcomings compared to the best of single ended portable amps. It doesn’t quite have the composure of high quality single ended amps, the mid range, the soundstage depth, image, and coherence, and so with highly resolving headphones like the HD800, I’d still take the Continental or the L3 over the Mk3-B. I think the sound is a bit grainy and not as clean as the Continental and the Triad Audio L3. I did enjoy the sound of the Mk3-B and HD800 pairing, but I just felt that it’s not the best combination that I’ve heard the HD800 out of.
Compared to the other balanced portable amps in the market, the Mk3-B indeed is the best implementation I’ve found as it really has the guts to drive difficult headphones up to the Hifiman HE-6, while the SR-71B and the PB-2 amps fall short.
The Mild Bass Boost
Initially I was disappointed to find out that the Bass Boost knob only adds mild amount of bass to the sound, while I was expecting something more aggressive like on the L3. I don’t like having excessive bass, but I like the fact that I still have some extra reserve on the boost, even if I end up only using 30% of the available boost most of the time.
Turns out that the ALO guys likes roughly the same amount of bass boost as I do, only they decided to set it that I have to go all the way to the 100% level to get it, instead of the usual 30% on the other amps. I like the bass boost and I constantly use it around the 90%-100% mark. I find that with the bass boost on that position, I get a fuller bodied sound that reminds me of the National, whereas with the bass boost off I’m back to the same sound of the Mk1 and Mk2 Rx amps: spacious but not so much midrange body.
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