In late 2014 I emailed ALO asking them what is the game plane for 2014/2015 and they had a few ideas in the pot but otherwise I felt they had a fairly quiet year in terms of big ticket releases. The fact they didn’t have a table at CES2015 actually got me a little worried that perhaps the ALO Audio juggernaut had ground to halt a little. Yup we had some nice revisions of the National and the International but nothing seismic or show stopping. Glad to say with the release of the reinvented RX IEM amp over the last few weeks that is not the case at all. The revamped tube amp/DAC Continental may have stolen the show at CanJam 2015 SoCal but at $299 (promo price) and standard SRP $349 the RX portable amp might just hit the sweet spot for a ton of IEM users out there searching for something a little special and blissfully noise free. Yes it’s an oldie, their first ever amp was indeed the RX amp, but the thinking on this one is all new.

The RX Line

For those of you who have been into portable amps for more than a few years or tracking the rise of ALO Audio will know that before they adopted their neo retro geographical/travel style branding of the last few years they actually started out with the RX brand which is still with us to this day. The original of course was the iconic RX (mk1 shall we say?) and then the RX2 around 2010 followed by the RX MK3 (multiple versions) that they sell right up until today. My first actual exposure to ALO’s fabby range of amps started with the RX2 in September 2011 when I was stacking with Cypher Labs SOLO DAC back in the day when bypassing an Apple DAC was something unique and standout rather than the standard you find today in many amp manufacturers. The RX2 was the perfect physical form factor and match for the SOLO at the time, sporting a jog dial for volume much like the original, a hi/lo gain option and was a considerable size increase on the original RX portable amp partly due to the need to match the SOLO form factor for stacking purposes.

The RX MK3 went even bigger and opted for power and balanced to the detriment of IEM users because the one thing that really the RX series didn’t really cater for was the IEM crowd. The RX3, while seriously good for the planar crowd was, and still is, a bit of a noisy chap when it comes to highly sensitive Earphones. The RX range started out with the powerful RX amp but increasingly becoming all about power and headphones. Well fast forward to 2015 and the big money is now on a revitalised DAP market and ever rising custom monitor usages (and prices!). That market is all about sensitivity, low to zero noise floors, low impedance output and something very pocketable. If you are going to do an analog portable amp these days you have to bring something special to the table because convergence DAC/AMPs like Oppo’s $299 HA-2 does a hell of a lot for the price.

Modern Retro

ALO have responded to that market challenge by reintroducing the new RX as an analog amp geared to IEM users and out of the little black retail box it is clear that portability with a modern take is high on the list of features for this new iteration. The form factor is classical portable amping in its lines producing a very familiar feel to its handling and stacking capability. Measuring in at a very tidy 2.28×3.64×0.69 inches in diameter and plated with a very retro looking and stylish nickel plated CNC’d aluminum enclosure the RX is a very striking diminutive portable amp. Now you may notice in the pics that nickel plating looks like it has pulled through a bush backwards giving it a rather fetching worn look out of the box. Speaking with the guys at ALO it would seem that the Nickel plating can show up oxidization fairly easily along with smudges and smears. Personally I think it is just dandy looking but if you want a perfect look to the casing then simply apply a bit of vinegar and it will look fresh as a daisy thereafter. Otherwise leave it alone, the worn look is perfect.

DSC00099

Both sides of the RX have an array of venting holes for heat dissipation. They also produce a nice little orange glow from the LED orange power on indicator located at the front of the amp or a similar LED light at the back which turns on when charging. To carry the RX portable amp ALO have kindly included a small padded cloth type pouch with a netted design and accented with an ALO Audio label on the side and a drawstring at the top for safe keeping when the amp is inside. Along with the pouch the RX comes with the usual ALO Audio branded straps for stacking and a USB socket 5v AC charger and a lush Green Line USB Cable.

The Plastic Pot

To the front of the RX ALO have done away with any fancy gain circuitry and gone straight for a simply analog line in and headphone jack out in 3.5mm format with a silver coated metal ALO knob over a plastic element type potentiometer. The plastic potentiometer is a deliberate move by ALO away from carbon based variants which tend to have a shorter life span and. The reliability of the plastic is also normally preferred to the carbon based variants given they are traditionally a bit quieter than hot formed carbon when in use. Carbon tracks wear and tear fast and often in a very uneven manner leading to scratching and long term channel imbalance. Precisely the very issues this new RX wants to avoid if it is going to appeal to IEM users.

DSC00101The Green Line

To the back you have a touch of the modern with a micro USB charging port (5V DC from USB bus) and an orange LED light which turns on when connected to either your PC or the accompany USB charger and cable and then green when charged. This is a bit of a change from the normal 9 or 12v AC charging circuitry they had in previous units such as the RX range and the National/Continental type units and more in line with their smaller Island DAC/AMP which was also USB charged. Thank god for that actually since am I already coming down with a ton of chargers that I constantly need to label to prevent unwelcome voltage related accidents. You also get that nifty Green Line branded micro USB cable that when I checked ALO Audio’s online store sells for a whopping $149. That just makes this the second most expensive USB cable after the Kingrex splitter in my collection. Handsome USB cables are always a welcome edition and this one is no exception with a solid green sheath and gold plated micro and USB A connectors.

Page 2: Sound Impressions

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About The Author

Editor

Founder & Owner of headfonics.com. I first started reviewing in the late 80s (ouch!). Back then it was albums, rock concerts and interviews with a typewriter for the local rag. Now its desktop/portable and digital 2.1 audio on a rather nice laptop. How time flies.

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  • Cotnijoe

    Thoughta compared to the pure II?

    • headfonics

      I have the Duo not the pure 2. Different sound signatures. The Duo is Warm almost tube like tonal quality with faster transients, a coherent bass and a very slight roll on the highs. The RX is neutral, thinner, speedier and more dynamic.

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  • Boogie6301

    I would usually audition any headFi gear before purchasing. The Rx is a very rare exception and I relied a lot on the review here. The sound impressions from the review is spot on to what I’m looking for. The Rx looks great specially with my iMod.

    My excitement lasted just moments because when I powered this baby up the output was really low. I understand that it is optimized for IEMs but should have decent gain for small to medium cans like my HD25-1 II or even my LCD-3. It also says that in the review.

    With my 1964 V6-Stage my normal comfortable level is already around 3-4 o’clock. At full volume you can really hear distortion. It sounds great matched to the V6-Stage at mid volume but for all my other cans and iems it was a disappointment. I’m sure it has nothing to do with my cable or player because when I tried a stock iPod Video and LOD the volume level is the same. Interestingly, using the Fiio X1 as my DAP the volume was loud even at 12 o’clock with the HD25-1 II.

    I think I pulled the trigger on this one too early. It seems it doesn’t match well with the iPod ecosystem – I should have waited for more reviews. However If I got a dodgy Rx I really would like to know. I’ve been emailing the ALO helpdesk for 3 days already and all I got was the auto-reply acknowledgement.

    • headfonics

      It may have something to do more with your output on the iPod video than the RX as in all test I did use a DAP given this is an analog amp and will not decode anything so in effect you are double amping. Did you try the X1 into the RX?

      Try using the source volume as a pre amp so you can get the right setting which is what I basically did using the DX90 and the Ak120 and the Glove A1.

      It will power what you need to varying degrees beyond an IEM that I am 100% certain off but the volume pots on all my sources where set to different levels to compensate.

      • Boogie6301

        Thanks for the very quick reply.

        I tried your suggestion but (1) the gain was more at only the iMod max volume (I’m using Rockbox by the way), (2) it defeats the purpose of the iMod where the inferior analog output stage is bypassed and (3) yes, I used an X1 with the Rx and the volume is as expected via X1 line out setting and not headphone with variable volume.

        I haven’t made measurements but I’m assuming when you use the line out on a player, regardless if it’s an iPod, Fiio, AK or any other DAP the voltage should be at or near the standard 1Vrms. I also have the JH16/JH3A combo and my iMod works perfectly on that one – although the JH3A digitizes the analog input for its DSP before converting it back to an analog out to the JH16s.

        Oddly I’m hoping my Rx is just a case of a manufacturing defect (so I can just have it replaced) because I really like it’s sound signature similar to my Pure II. However, If this is the way it works – most likely I’ll return it.

        • headfonics

          Hmm.. my test setup was the DX90 on line out and the AK120 with the Glove A1 in line out also. In both cases I did some manual adjustment to get the right balance for using th RX.

          For the DX90 it was low gain line out, not so sure on the precise volume setting to the A1 since the A1 has not precise guide compared to the AK120.

          For the Prime match it was the AK120 and the Glove A1.

          I might give the RX a spin with my old iPod 7th gen this weekend and see what happens though to be fair I stopped rockboxing a while ago.

          • Boogie6301

            If you can test it on an iPod that’ll be great and I’d appreciate it. I had the same results on a iPod U2 5.5g as with the iMod. Testing it on a 7th gen should be close enough to validate or dismiss my observation. I’m looking forward to your tests. Thanks a lot.

          • headfonics

            I can throw on the Nad HP50, senn momentums and some of the original IEMs I had tested just to see how portable cans stack up using the iPod/RX.

          • Boogie6301

            Hi,

            I finally got a response from ALO support

            “…..The Rx is a IEM (In ear monitor) only amp, not meant for headphones so If your using the Rx with Sennheiser HD25 then yeah it will not have enough gain. The Rx page is pretty specific about that it is a IEM amp. I would use it with IEMs only”

            It still didn’t explain why when using other sources like the X1 the gain is more than enough. I asked for more specifications like input voltage and impedance because I believe this is a matching issue with the iPod rather than power.

          • headfonics

            The X1 is not that sensitive with IEM’s compared with the RX for me though, has a bit of hiss now and then and higher noise levels.

            Will be checking that iPod match up shortly after my nightly Vikings episode catch up 🙂

          • Boogie6301

            Thanks. Looking forward to your iPod+Rx impressions

          • I’m way behind in that series.

      • There is nothing wrong with double amping.

        • headfonics

          Depends on the two amps.

          • It depends somewhat. If inputs and current-to-voltage outputs are designed properly, it really doesn’t matter.

          • headfonics

            Says who?

          • It is all maths. There is no magic or synergy to it. ‘Synergy’ is all down to personal preferences. But actual performance of the output to the input of an amp, come down to simple mathematics.

          • headfonics

            What are those simple mathematics? Sources pls? Anyhow this is OTT since you misinterpreted my original statement when I did not state double amping was wrong. 😉

          • 24bit

            This is a half truth.

          • I think you’ll find electronics to be a purely mathematical thing. What you like in sound, however, is 100% personal. Properly driving signals is 100% maths.

          • 24bit

            I’d probably do the same thing, I’d keep it in the glove and output it to another amplifier, instead of taking the dap out of the amp. If the glove increases the sound quality or alters it from the player alone, then that is always the wiser choice if you need more power in a larger amp. Maybe I am not reading this right, was that the argument happening here? haha. Just curious 😛

            Synergy is a hell of an important factor in your rig and is the direct result of great “maths” as you put it. Bad “math” probably won’t result in a specific desired tone, would only happen as a fluke.

          • Synergy comes down to personal preferences and there is no accounting for them but by me saying I like A and you saying you like B.

            That aside, driving ability, ability to resolve and sustain input signals and output signals is 100% down to maths: the current sustained at a specific voltage. it is all maths.

            But manufacturers can do what they want to affect those maths: add distortion through various means, lower or raise input or output impedances, use caps, or other in the signal path.

            SQ is hardly ever what we reviewers write about. We write about what we like. And there is no accounting for personal preference. I wish we’d be more honest about that as SQ is something for which no definition exists in the audiophile world.

            The audio world is as plagued by lack of measurebators as the photo world is plagued by them. I’d prefer a better balance.

            All that is to say that ‘desire’ is the product of a specific preference. And Preference is the object of a person, not a standard.

        • headfonics

          Just thought I would mention Nathan try to re-read my first statement – it says I am double amping my glove combo to the RX rather than stating his problem is double amping.

          My contention was maybe the amp of the ipod is not a good match for the RX amp – remember the second amp just adds gain to the flavor of the first amp unless the second amp has a poor design to begin with which the RX does not.

          Through testing the RX through my own double amping with the Glove A1 I found the results more than acceptable.

  • Goggs

    Can I just ask how you paired the AK120 + A1 with the RX? From what I know, there is no lineout option for the A1, so I would supposed you took the analog out from the A1 directly into the RX, essentially meaning double amplification?

    • headfonics

      Thats correct.

      • Goggs

        Cheers. Does the RX really improve on A1 HO itself? I’d be somewhat doubtful considering the A1 is pretty good by itself, and double amping isn’t such a good idea for many people.

        • headfonics

          Its more of a difference thing and I was testing it for something else at the time so why the heck not. The RX is very transparent anyhow so you get all the goodness of the A1 with the control of the RX for more sensitive IEM’s.

  • Barry Rosekind

    how does it sound with JHA customs? more specifically the 16s?

    • headfonics

      Sadly I do not have any JH customs to test it wit h but most other high end customs I have sounded good, particularly if the custom exhibiting an already excellent soundstage and a natural response. (VE6X, Custom Art Harmony 8, UM Merlins etc)

  • stas

    hey 🙂 but have this amp also DAC?? i m looking for amp/dac betwen 180-200-250 $.. and i listen Korn and heavy stuff. i hope you will find a good amp/dac for me 🙂 . cheers from Belgium

    • headfonics

      Just a portable amp but made specifically for efficient IEMs and cans. For that budget I suggest Ibasso D14.

  • Eddy

    I have dita truth ak version and ak120ii, do I need this little amp?

    • headfonics

      No not really.

      • Eddy

        Thanks

      • Eddy

        Btw, I am always wondering how dita truth is compared to those a flagship CIEMs. Are they at the same level in terms of soundstage and tonality? I know it sounds like a stupid question, but I cannot help noticing u choose truth as the daily equipment instead of CIEMs. Your advice will be so valuable because I really want to know whether I should upgrade to ciem.

        • headfonics

          Oh i used the Truth for comparisons but in truth I use a wide range of iems and ciems for daily use chiefly the Campfire Audio Jupiter and the M-Fidelity SA-43 in the last few outings. I am always a firm believer of ciems.

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