JustAudio µHA-120: Size Doesn’t Equal Quality! – update with AHA-120


A few months ago we reviewed JustAudio’s AHA-120 amplifier and we found it was a great amp. Now it’s time to review its little brother, the JustAudio µHA-120.

Unlike the AHA-120 (A class), the µHa-120 is the (more) portable amp of the two and it is a so called AB class amplifier. The version we received was a revision B, fitted with the optional “white velvet” pot upgrade. This more “basic” version of the AHA-120 doesn’t have the impedance selector on the front but uses jumpers to change the maximum gain setting. Ours was set at 6dB/12dB by Justin himself. Changing the jumpers is actually quite easy with the toolkit provided: with the hex key and battery tool it doesn’t even take 5 minutes to change the jumpers.

Both versions have a selectable power source (APSS). The specs for the µha and the AHA-120 are the same:

As you can see the maximum power is 56mW when using the USB power supply (32mW when battery powered). This is quite a noticeable boost when using a 300Ω headphone but even without the USB power the amplifier is still powerful enough.

Overall Sound Impressions

Right out of the box it sounded rather disappointing but that actually changed fast after a few hours and it has only gotten better. Soundstage of the µha-120 is definitely good, I’ve been enjoying it since the beginning, and as I already mentioned in the B&W C5 review, I have been using it nonstop. This little gem is neutral, it does not color the sound in any way. It’s very detailed in all layers, delivers great deep bass (it sure does have depth) and to my ears smooth nice mids and detailed highs. If I have to say anything it would have to be that it does emphasizes the bass, but I like it that way. I really can’t say anything wrong about the µHA-120, it has great resolution and it doesn’t sound airy or forced in any way. It sounds just right!

Justin insisted not to only consider this amp as a portable one and he suggested to hook it up to a stand-alone dac, and was he right… Its performance is way above what you would expect from a unit of this size, once again showing of its neutrality and driving everything from an Audio-Technica M50 to a Hifiman HE-500. Of course there is a difference between a full sized desk amp and the µha for what “body” is concerned but it does the job more than just ok.

I’ve been using this amp with my iPod, my laptop and at home and not one single combination has disappointed me in any way.  For all music styles I listened to, it was very realistic in portraying the instruments and it actually does great for all musical styles.

Comparison to the AHA-120

The A-class AHA-120, has a slightly different sound signature. The sound is much clearer and the soundstage is a lot bigger and more balanced. In lows, highs and mids everything has far more resolution and overall it is much easier and relaxing to listen to. Unlike the more portable µha-120 the focus isn’t on the bass section, there’s not really one point of focus. You get a less powerful bass as with the µha but it is far more detailed, the difference is very noticeable to say the least.

Both amplifiers have more than enough power you need and the advantage of the AHA-120 is that the impedance selector on the front allows you to slightly modify the AHA-120 according to you preference and headphone used but the differences are very subtle. The main goal of course isn’t to change the sound signature but to optimize the power supply so you get the best result for your headphone while not wasting power. (We explained this in detail before).

Since we last reviewed the AHA-120 in detail, JustAudio has modified its casing and now it has the same excellent build quality as the µha-120. The size of course is remarkably different but that’s the price you pay for an overall more qualitative sounding amplifier.

For those listening at home who prefer an even more balanced and detailed sound and a larger sound stage, I would recommend the AHA-120 which overall just has more quality. The fun award for me still goes to the more portable µha-120, it’s just great for when on the move.

Headphone Pairings

My beloved Sennheiser HD650(300Ω) was my favorite headphone at home with this amp and it was very enjoyable with good bass. The new Beyerdynamic T70 (250Ω – review coming up soon!) is easier to drive than the HD650 and the µha-120 does a great job, I’m convinced that the µha with the portable version of the T70, the T70P (32Ω) would be a killer combo! The little µha-120 performs exceptionally, even with big orthodynamics like the Hifiman HE-500 and the Audez’e LCD-2. They are the biggest challenge for this amp but at high gain it does get the job done more than just fine. Of course the volume has to go up a bit more then with the other headphones but it actually sounds very good, another positive surprise proving that this isn’t just a small portable amp for IEMs. That being said, with all the IEMs I tried, it did a great job.

Being honest I have to admit I do have some remarks as well. One I already mentioned in the C5 review and it’s about the plug. As the C5 IEMs can be used with an iPhone, the plug seems to distort the sound but by pulling it out for about 1mm it gets back to normal. The other remarks are about the volume dial. When using sensitive head/earphones, you can hear the music playing very very softly at zero volume and at very low listening levels there’s some channel imbalance, but all of this is minimal, it didn’t bother me at all. The other issue with the volume pot is the strong increase in volume between 9 and 10 o’clock which is more audible. Besides all these (for me) smaller issues the volume pot is very precise and very smooth to turn.

Design and Built

The look of the µha-120 is fairly basic, the front panel has the 3.5mm in/out, the LED and the volume dial while the back is the same as the AHA-120 with the charging and battery/usb option switches and the usb connection. It might not be as flashy as some other amps on the market but the build quality is very good and it feels great in hand, very robust. Height is 23mm, width is 52mm and length is 85mm which makes it about the same size as a pack of cigarettes, which means it fits in your pockets. Compared to something like the Fiio E11 it is twice as big, but it is also twice as good, at least. But seriously it really do is smaller as you think looking at the pictures. I like holding my portable rig in my left hand while on the move and found it very easy to adjust the volume setting when needed.

Charging the battery (only via usb) goes fast even at the normal setting and one charge lasts long! JustAudio claims up to 24 hours of operation time and I’ve been using it daily for about 5 hours a day and only after almost 1 week the LED indicator started blinking. For those always forgetting to reload their devices this is good news. Do be aware that when the LED finally does start blinking the µha will be shut down reasonably quick.

End Words

Justin and JustAudio have done it right again with this amp. It does everything you want it to, it sounds great, it is portable and it can handle about everything there is on the market. It’s pretty obvious that I love this amp and I can only recommend it. I won’t ever again say it’s “just” the AHA-120’s little brother, that’s for sure. I’m really sad to send it back to Justin. As a matter of fact I think I’ll mail him to buy it from him. I think that sums it up best: The µha-120 is a keeper.

Thank you Justin for giving us the opportunity to review another of your products and for making such a great amp within the £200 price range! More info about the British JustAudio and where to buy the µha-120 can be found on their website.

Gear used for the review: Hifiman HE-500, Audez’e LCD-2, Sennheiser HD650, Beyerdynamic T70, Audio-Technica ATH-M50, Fischer Audio Eterna Rev.2, B&W C5, Audio GD NFB3, Ipod, ZYCABLE Hi-end II LOD, iPad, Dell Laptop.


Mike has also written a review on the AHA-120.


Rate this review


Lieven is living in Europe and he's the leader of the gang. Coming from a musical family he's always been interested in good sound. Unlike his family members the only musical instruments he plays are amps and DACs. He loves playing with old tubes and discovering new products while staying faithful to the good old Sennheiser HD650.

  • Anonymous

    We will try to update this article with a short comparison to the bigger, AHA-120 amplifier from JustAudio which we have reviewed earlier.

    • Update coming very soon!

      • Dookie182

        looking forward to read it lieven. I’m more and more teased my this little unit. I guess I’ll have to start saving up!

  • Mike, try with T1 and DT1350

  • Andy Smith

    I bought one of the first uha-120 from Justin (series No. 0009) a few months ago and recommended that Mike review it along with the AHA-120. I use my uha-120 daily and it’s astonishingly good, relatively pocketable and supremely musical. Whilst it might not have the nth degree of resolution and can overdo the bass response on occasion, it’s become my portable amp of choice and is equally good playing compressed MP3 files as it is lossless music. To give you some comparison, I prefer the uha-120 to the RSA 71a, Pico Slim, ALO Rx II and the Audinst AMP-HP.

    • Anonymous

      Yes thanks for recommending it to me, Andy. 

      This review was done by Lieven, but he seems to extremely like it and he’ll add in an impression of the AHA-120 as well, perhaps next week. 

      • Correct Mike, I will be updating the article with a short AHA-120 comparison as soon as possible

        • Anonymous

          Looking forward to it, Lieven.

  • Mast3r_5ega

    Nice review! 😀

    How about compare it with, say Corda Stepdance? 😀

    • Hi, I don’t have the Corda stepdance so I can’t directly compare it. But in general the Meier devices sound much more analytical (than fun).

      • Anonymous

        Yes the Stepdance is a bit dry and analytical.

  • really nice pics. so refreshing.
    perhaps you should do more outdoor photo shoots in the future.

    • Thanks Mas, I appreciate that more as you can think
      Right Mike? 😉

    • Anonymous

      Yes, thanks. I think Lieven’s pictures are very nice and refreshing. I tried to tell that to Lieven but he wouldn’t believe me. 😉

  • Sorensiim

    My µHA-120 should arrive early next week… Can’t frakkin’ wait!!

    • I’m sure you’ll like it 🙂
      Are you joining the picture contest Sorensiim?

      • Sorensiim

        I’d love to if I can find the time – and a model 🙂

        • Anonymous


    • any early impressions?

      • Sorensiim

        Sure: IT KICKS ASS!

        I cannot believe that this little thing packs such a punch, yet manages to sound so clean. It’s a great addition to my Cowon player while on the go or at work and even better at home when hooked up to my fullsize DAC. (Yulong D100). 

        It really adds some impressive depth to the bass, but does so without blurring the rest of the spectrum. Voices sound so natural and no matter what I throw at it, it just sounds so effortless. Rammstein with the uHA-120 and Ultrasone Pro 900 is nothing short of amazing. Punchy and fast, yet very detailed and natural sounding. 

        • It’s really is nice sounding. I’m sure you’ll like the E10 soundsignature as well.
          Mental note: try E10 dac + µha-120 later

        • Anonymous

          Damn, sounds really kick ass indeed.

  • Sese

    Hi Mike, I got the uHA-120 from Singapore. I was given the Graham Slee to compare but I can’t avoid how neutral this little amp sounds. It sounded great with the UE TF10 and everything we plug into it. Very clean sounding indeed!
    Thanks for the review. You made me to be more of a proud owner. Still on burning period and am loving it. BTW, I got the revision Serial Number B041. hehe

    • Glad you like my review. Enjoy the µha-120, burn in goes pretty fast

      • Sese

        I did, Lieven! Thanks. I taught Mike wrote it. I did not see the author. Sorry.
        More than 30hours running now.
        Is the runtime 24-hours? I am surprised I made 18hours on High Gain using Philips SHP895, pot set to 1 o’clock, and another 10 hours on low gain at 3 o’clock. At the 28th hour I just had 1 blink. And opted to recharged.

        • I found battery life to be exceptional as well

  • Dookie182

    that might be a silly question, but did someone (lieven maybe) have the occasion to compare the uha 120 to the burson ha-160.
    I’m currenlty having a pair of denon ah-d2000 headphones and listen to lost of music type, but still with a thing with fast paced, rock punk ska or hardcore music.
    I bet both amp deal nicely with prat and bass handeling.
    maybe the burson will tend more to the warm/bodily/analogue side of musical and the uha 120 more on the natural side of musical?
    any comment is welcome 

    • The Burson is ahead of the µha at all levels, you can’t really compare them. I think the µha is warmer and the burson more musical. The µha is good too, but smaller soundstage, less detail, etc. There’s a huge price difference between the 2 as well, it’s only normal. If I had to choose and had the money then I’d go for the Burson, if you want something cheaper, good but very fun go for the µha. The Burson is also better for faster music imo. hope this helps

      • Dookie182

        thanks a lot lieven, at least it makes things clear,
        I’ll start saving up for the burson.
        kindest regards

  • Kowloonmotorbus1933

     HI, may I ask how does it perform comparing to TTVJ slim? Thanks.

    • I didn’t have the opportunity yet to listen to that one, sorry

  • Hey Mike, curious comparison but compared to the more recent Alo National, which of these is better in terms of musicality and warmth? Would also like to know if the uha120 would be a better pairing with a senn hd650 than the alo national, thx again!

    • Hi Nick,
      I can’t say as I’ve never compared the uHA to the National side by side. Reading from Lieven’s impressions, and extrapolating it *somehow* to the bigger AHA-120, I think the uHA-120 should be comparable to the National.

  • Damián Bonadonna

    Hi Lieven/Mike,

    How does it compares to the C421? As they are similar in price and portability.

    Thay about JDS CMoy?

    I also wonder why the C421 is not in the recommended amp section.


    • I will have to let Lieven answer this.

      The C421 should be in the recommended amp section. I just haven’t updated that article in a while.

    • L.

      It’s been a while since I listened to the µha but if I remember correctly, the soundstage on the C421 is a bit wider. ùha is more compact with a bigger focus on the bass. It’s a bit more expensive but it does have a better volume pot. Overall the C421looks to be the better buy but I really loved the Just audio Amps too. Tough choice but I’d go for the JDSLabs, if not only for it’s size 😉

      • Damián Bonadonna

        Thanks L.

        I’m waiting for my Dacport LX to arrive :). I will see how it behaves without an amp. I have HD598, EPH-100, SE215 and HTX7. So all easy to drive cans/IEMs.

        I am reading that a lot of people says that I don’t need an amp for those. So I was thinking if maybe something inexpensive like a CMoy (I don’t like that it doesn’t charge by USB) or an E11 would have the same effect on my set up as they are all easy to drive.

        What do you think?

  • Ryan

    How much more refined is the AHA 120? Is it a big noticeable difference?

    • L.

      yes, the difference is pretty huge