Review of the Just Audio µHA-120 – Don’t let its size fool you

Pros: Sound quality, excellent transparency, well built, small size, battery life
Cons: Price, volume knob

Build Quality: 10/10
Design & Look: 9/10
Functionalities and ease of use: 8/10
Audio Quality: 10/10
Value: 8/10
My final Rating: 9/10

Purchase Date: September 2012
Purchase Price: £220

In September 2012, I was extremely lucky to win a raffle prize during an audio meet. When I went to pick up my prize, I had to choose between headphones I wasn’t too keen about. Then a little brown box was pointed out to me, and I wondered what was inside. I went ahead and opened it and after seeing what was inside, I immediately claimed the prize. What laid inside the box was this little amp called the Just Audio µHA-120 (JA uHA-120). At first I didn’t know what to expect, but after plugging it in with excitement, my face lit up in joy. The company behind the amp is called Just Audio, and the name of the owner of JA is called Justin, who runs everything that relates to the amp.

The JA uHA-120 can be purchased from HiFi Headphones for £220
More in-depth information of the amp can be found on Just Audio’s website, where a full description of the amp and a guide on how to change the jumper settings can be found.

Just Audio µHA-120 - Side View

For my initial impressions and unboxing video – Click here

The amp comes in a small box, where there is included a hex key, a plastic tool to change the jumper settings, four rubber stickers to affix at the bottom of the amp, a usb cable and a card from Just Audio. Please note that the 3.5mm to 3.5mm interconnect that is pictured isn’t included, however was included in the raffle prize I received.

Just Audio µHA-120 - Package Contents

Build Quality

The build quality of the uH-120 is very good indeed. It has a solid metal casing, that is sturdy and well built. The amp can be taken apart, in order to replace its battery, or to change its jumper settings. The front and back panels of the device are coated in order to protect it from long term wear and tear.

Just Audio µHA-120 - Side View

At the front of the device an input and output jack are present, with a little yellow LED light to demonstrate when the amp is on. To turn on or off the amp, it is as simple as turning the volume knob.

Just Audio µHA-120 - Front View

To the back of the device, the USB input in order to charge it is present (note that this is not the DAC version, although there is a DAC version available for purchase separately), and there are two switches, one to denote how fast the charge should be (normal is usually used for those with slower USB slots, and thus fast charge is the best way to charge your device with speed) and finally there is an APSS (Amplified Power Source Select) switch with it written BATT (for battery) and USB – this switch effectively denotes where the power should be drawn from: either the USB wire that would be connected to a charging port, or its internal battery. The APSS also denotes how much power the uHA-120 can produce, thus meaning if you need something to be powered a bit more efficiently, then the APSS on USB whilst it is connected to a power supply, will give you that extra bit of power to drive those high impedance headphones.

Just Audio µHA-120 - Back View Just Audio µHA-120 - Back Angled View

Finally, a note should be made about the battery life: I found the battery life to last long, much longer in fact, when the device was charged via the “normal” pace of charging. The average battery time, of it being in constant use at around 60% volume was around 10hrs (after being fast charged), and a phenomenal 20hrs (after being normal charged). The charge time is up to around 6 hours on the normal charge setting, and around half that on the fast charge cycle.

Just Audio µHA-120 - Screw inputs Just Audio µHA-120 - Battery Cable Just Audio µHA-120 - Battery

The only little drawback about the JA’s build quality is the volume knob. As this headphone amp is supposed to be partially an on the go amplifier the volume knob I feel is a little loose. By that I mean it can be mistakenly turned without the intention of changing the volume. Although this isn’t a huge issue, it is one to note down for the portable users that want to use this amp on the go, and might have the amp moving around quite a lot in their setup.

Just Audio µHA-120 - Front View

Overall, the build quality of this amp is brilliant and with its solid construction is an amp that can withstand quite a lot of wear and tear. I love Justin’s attention to detail throughout the amp too, which shows care and professionalism.

Functionalities and Ease of Use

As explained above the APSS is the main functionality that changes the way the uHA-120 is used, but apart from that it is as simple as plugging in your input and headphones/earphones tot he amp, and enjoying the music.

Just Audio µHA-120 - Back View

Thus meaning the ease of use is extremely easy, and anyone can work out how to use it.
I should mention that within the functionalities the jumper settings can be changed, and this is to effectively change the amps gain settings from high to low gain. It isn’t as simple as it should be on some other amps to change the gain settings, which is a slight shame, however if you’re one not to constantly change settings, then it shouldn’t be a problem. However that’s the reason why I dropped the rating a little on it as, even though we have the option to open up the amp and change the jumper settings, it isn’t something that can be done with a simple click of a button, for example like on the EHP-O2D desktop amp. The procedure, after doing it once, becomes something one can do in a matter of minutes, where the longest part of changing the jumper comes from tightening the screws.

Just Audio µHA-120 - Jumper Settings on Low Gain Just Audio µHA-120 - Board Just Audio µHA-120 - Rear board Just Audio µHA-120 - Screw inputs

Overall, the functionalities are as simple as it gets and the ease of use of the product are quite simple, apart from when you want to change the settings of the amp.

Sound Quality

The sound quality of this amp, is what really surprises me. It provides an absolutely transparent sound, that I’ve never come across before. It beats the EHP-O2D, in the respect of being truly transparent and more so not tainting the music you’re listening to in any way. The way Justin created such a marvel, in such a small casing is beyond me. It does so much right, and absolutely nothing wrong. I couldn’t find a single flaw in the sound, and more so without the uHA-120 plugged in, I felt like something was missing with my music. The crisp, transparent sound the amp outputs is just splendid, and makes you think: “How does something so small, produce this?” It is indeed a small device, but as some might say, size isn’t everything. I can’t have imagined a small amp like this to really improve the sound quality in that respect. It is only something you have to hear in order to understand its pure brilliance. Designed from the ground up, Justin at Just Audio, knew what he was doing, and this uHA-120 ticks all the right boxes and more. It actually got me curious as to what its bigger brother, the AHA-120 sounds like!

Just Audio µHA-120 - Connected & Playing

The key defining term for this amp is transparency, no colouring of the input sound, clear and crisp reproduction, and more so 0 distortion at MAX volume. Its ability to drive headphones is extremely good, and I’m quite confident that this can drive high impedance headphones, although maybe not as well as my EHP-O2D can do, but going past the 80% volume mark on the uHA-120 becomes ridiculously loud, to the point that if you’re listening to music that loud, you are most probably deaf!

Just Audio µHA-120 - Dimensions Just Audio µHA-120 - Dimensions Just Audio µHA-120 - Dimensions

Overall, the sound quality is perfect, I can’t stress that enough and just like with any amp, it is hard to explain the sound quality and all round goodness without you actually going out and hearing it for yourself.

Conclusions and final thoughts

Just Audio µHA-120 - Connected to my SGS3 Just Audio µHA-120 - Connected to my SGS3

The sound quality is by far the strongest point of this amp, it does exactly what it is supposed to do. However at an extremely high price for what it offers, I find this amp in a niche market, for people looking for portable transparent sounding amps. Amps like the E11 for example, would satisfy most users at around 1/4th of the price of the uHA-120. Which thus means that this amp appeals to people who are really picky about the sound they are getting. That said, this is the best amp I’ve heard to date, that is portable and small sized, but all that comes at a substantial price of £220, which I personally wouldn’t be able to justify, if I were purchasing it myself. To give you an example of the competition, the FiiO E11 is around £60 and the EHP-O2 is only £100 (DAC version £190). So, this gives you an idea of the extra premium you are paying for that extra bit of transparency and build quality.

Just Audio µHA-120 - Connected to my SGS3 Just Audio µHA-120 - Connected to my SGS3

If you are serious about audio, then you shouldn’t look any further than the Just Audio uHA-120, for a very worthwhile purchase of an amp.

I should also note that Justin made me aware that since, the product has had some modifications done to it:
“newer batches have adopted improved (weightier feel and tighter tracking specifications) parts”
Which just goes to show the commitment Justin has in his products!

Hope you enjoyed my review!

4 thoughts on “Review of the Just Audio µHA-120 – Don’t let its size fool you

  1. Beaver

    thank you for the review i needed to research the Just Audio uHA 120D before i purchased it to addon to my Astell & Kern Mp3 MQS player.
    I noticed in your youtube video review the battery part number was blacked out for obvious reasons !
    I have managed to remove the marker pen masking to reveal the battery part number & thought i update you & others who wish to locate a spare for future use.

    Direct Link To Picture If The Embed Code Fails:

    Keep up the excellent reviews

  2. thatperson

    “The sound quality of this amp, is what really surprises me. It provides an absolutely transparent sound, that I’ve never come across before. It beats the EHP-O2D, in the respect of being truly transparent and more so not tainting the music you’re listening to in any way.”

    That makes no sense whatsoever. The O2 was built to be absolute transparent to the end-user and thus from the audio chain; there’s a whole blog dedicated to the design of the O2 and why specific components were used and tested with double blind tests. How can something be more transparent than transparent itself?

    1. TotallydubbedHD Post author

      It makes sense if you hear both. The O2D is an excellent amp and is very quite transparent itself – but has a slight “warmth” and “tone” to it, when compared to the Just Audio uHA-120.


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