The Power Pack: ALO RX MK3-B


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 Power

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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  • If you happen to own the Hifiman HE-5 (the original). I have just tried it on the RX Mk3-B running balanced, and with the Hifiman leather pads, the sound is absolutely amazing. The best I’ve heard the original HE-5 with. Obviously the leather pads help in taming down the treble, but the amp strikes a brilliant synergy as well.

  • Hmm, for the HD800, how would you compare the Mk3 to the SR71b? I really like the hd800 because it has the pace, punch and attack of a grado (almost) so its good for metal, but also an incredible amount of detail etc. so it is good for classic and other genres too. I’m sorta wondering if I should try switching to Mk3 and maybe even switch to a HE6 as well… Any thoughts?
    Cheers 🙂

  • No mention of very sensitive IEMs and how they fair.

    • I did Steve, please check page two. 🙂

  • Is the HE-500 or HE-6 best with this amp? Or to put it differently, can the HE-6 compete with the HE-500 out of this amp? Because having a speaker amp at home, the HE-6 would definitely be the best there… But on the go? 🙂

    • The HE-6 is much better than the HE-500 on the Mk3-B.

      • Mike, so you would say with HE-500 is not the best synergy with Mk3-B? Because currently im funding for HE-500 and go with portable DAC and portable amp. Do you have any suggestion mike? Sorry I’ve been looking for the answer in the net but wasnt any.

  • Trent_D

    You say the clarity is also good with this amp. How were the mids with the K550?

    • I think the mids are okay. Nothing particularly special but not weak either. You need to go with the Continental if you’re looking for nice mids. 😉

  • Hi Mike. I have the National right now, and I’m using it primarily to drive Ultrasone’s Signature Pro (it has the stock single-ended cable). I was wondering if the Rx Mk3 in single-ended mode only
    would be significantly better than the National.

    • Peter,
      It would be an improvement, but sound quality wise it wouldn’t be a big jump. The Rx Mk3’s main strength is the power output, which your Signature Pro doesn’t really need.


  • Hi Mike. I’m looking for an amp that works well with my Hifiman re262 and a Cowon c2. My budget is around 200 usd. Could you please help me? I listen classical, electronic and rock music. Cheers.

  • Andre Sneed

    Hey Mike love what you do over there! I’m looking for a portable amp to power my DT990/250 with some umph!! I have a e11 and it doesn’t feel like I’m getting the most out of my cans. I’m familiar with the Headstage Arrow and TTVJ Slim being some of the only portable amps that can drive 250ohm headphones properly. Doesn’t look like the Rx-MK3 will do the trick either… HELP!! 🙂

  • stan zorin

    “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…”
    Does the single ended output of this amp have the same sound signature / shortcomings as the balanced output ? How does this single ended output compare to the Alo Continental sound ?

    • Stan,
      The Continental is superior to the Mk3B single ended.

    • Less problems in single ended but if you want to go single ended the Continental is better

  • CLAS is source
    RX Mk3 is amplifier.

    Different things. Having both is good.

    • disqus_0ADxuk4tWH

      Does a source alter what comes out of my digital player, iPod?…I see they sell the amp/CLAS as a package, so I’m curious…are the benefits dramatic?

      • google dac ( digital to analog converter) understand what it is first and you can find your answer.

  • disqus_0ADxuk4tWH

    Thank you for the quick response…I await delivery breathlessly…

  • disqus_0ADxuk4tWH

    Excuse my ignorance as, I’m a newbie, I don’t know diff betwixt source and amp

    • Ipod, CD Player, Laptop + Medial Player, Walkman, DVD Player, Sony Playstation = Source Amplifier amplifies the signal before it reaches the headphones / speakers.

  • disqus_0ADxuk4tWH

    Hello all….myRx Mk3 has arrived…..but, alas, a cable is missing or I’m unaware of something I should have had…..can someone guide me?….seems I need something to connect Mk to iPhone…

    • Can you take pictures so I can see what you got?

  • disqus_0ADxuk4tWH

    Mike…..I just got my Rx Mk3…all it has is a power cord…there’s nothing to go from amp to source(iPhone, iPad, etc)…I’m not sure how to attach fotos here…ur kind for the response, so thanks

    • Yes you gonna need a cable to hook up the iPhone to the Rx. Better call ALO

  • disqus_0ADxuk4tWH

    Got it….anything I can buy at radio shack or Frys?

  • disqus_0ADxuk4tWH

    Mike…Seems I’m missing a “triple pipe L.O.D”….I wish I would have known, and, it’s another 200…goodness…what have I gotten myself into….thanks for ur time

    • You don’t need to get a triple pipe LOD. The one from Amazon would do as well.

  • disqus_0ADxuk4tWH

    I’ll DEF be looking at that…can a cable that’s an inch long be worth 200 bucks?…I’ll drive around and see if I can find one….uve been very kind…

    • You’re welcome, not a problem.

  • Gauchomb

    Hey mike, this is me, the rx mk3 newbie…thanx again…I’ll prob have more questions in future, I hope I don’t impose

    • Yes, no problem.

  • Gauchomb

    Hey Mike, rx mk3 is just great….size,weight,sound, defintion,amplitude were as good as defined and described…I use beyerdynamics dt1350 for bumping around and ultrasone pro 900 at home…is there something I can improve on?

  • Gauchomb

    Also, I run alot and bought westone ie2s, billed as the ultimate running earplugs…the actual plugs get saturated with sweat and flat out fall of my ear…in my call to westone, I was told that sweat “compromised” the seal of the earbud…do u know any other high end running headphones?

  • Nishy Wijewardane

    Hello Mike, Nice review. I have the HE-6+SR71B as my ‘portable’ gear (and EF6 as my unportable). You clearly say the ALO does a better job and I’m interested though I have no complaints on the SR71B: does the ALO give a better bass (for jazz); is the soundstage wider, does it have more power output, does it have a longer battery charge, and can it run on the same Silver Dragon balanced cables to the HE-6? Also what amps better than EF-6 with HE-6 can you point to? Have you reviewed the HE-6+EF-6 combination?

  • Vincent

    Hey Mike,

    Can you please tell me how far off between the mk3 and the mk1?


    • The one advantage the MKI has is the digital volume control. Smaller size is up to the owner. The digital volume control allows 100% perfect balance at all volumes with every headphone out there. If you are using single ended headphone or earphone set, the performance differences between the two are slim, but slightly in favour of the MKIII.

      The MKI was such a great amp that bettering it is rather difficult. While the MKIII is, overall, a better-performing amp, the MKI is a phenomenal piece of kit that will hammer it to most amps out there.

      • Yeah the Mk1 is special. Maybe talk to ALO to re-release the Mk1. 🙂

  • George Lai

    Hello Mike, can the same 9V charger be used for both the CLAS and the RX3?

    • If it’s both 9V then yes

  • George Lai

    And the newer model, the B+, is out.

    • Yeah

    • Yeah, bigger battery and supposedly improved sound. I’m still waiting for the store stock to come in.

      • George Lai

        Though I’m already very pleased with my CLAS -R and ALO National and Continental v3 as my main portable, or rather transportable, rigs.

    • It is. Both are great amps. If you are going to choose the best now, the B+ model may be the best investment, but if you already have the MKIII, staying the course is a great idea.

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