In today’s review, we listen to the Just Audio uHA-120 and the AHA-120 which are two advanced analog portable headphone amplifiers. They have since been discontinued.
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The clue is in the Name – Just Audio. Founded in the UK by Justin Harris in 2009 who has a first-class Master’s degree in Electronics and a background in the mobile communications sector he decided to switch in 2010 to portable amp development and not long after that out popped these two fine specimens – the uHA-120 and the larger brother, the AHA-120 portable headphone amps.
Now I have gone through a ton of headphone amps in the last few years but when I took these two little guys to the big meets last month there was significant interest and I can understand why.
These have been on the market for a while so those in the know will probably have read already a few of the things I want to draw your attention to but let’s start with the more emotional responses that I got from the meet before we do the nerd fest.
Background
Just Audio amps have filtered their way into Singapore resellers this year, in fact, I saw one I think around Dec 2011 but never got a chance to play with it. This time bringing both amps with me the same people stepped up to the plate with obvious sentimental attachment crying “Oh you have these? Let me try again!”.
And off the two amps disappeared for the best part of the meet with nothing but positive comments on both of them. Hard-nosed resellers grabbed them also and remarked on the build and design quality being way above what they are used to seeing shipping in from the East.
It was fair to say the amps generated excitement and interest more than I expected and it made me stop and wonder if these amps were perhaps a tad unique or special to get that kind of level of distraction from hard-nosed audiophile guys at the two meets.
AHA-120 Design
Both amps have roughly the same form factor but could be best described as the little and large show with the uHA-120 much smaller than the AHA-120. You would be dead wrong though if you thought one was just a miniature of the other.
In fact both of them present sonic presentations that for me target two different audiences or two different needs. The AHA-120 would be classed as more transportable than portable, in fact, a miniature desktop system would have the AHA-120 right in there and nothing would be amiss.
I have seen similar sized or bigger being carried around by our more hardcore members such as the Triad Lisa L3 or a dual-stack ALO Audio combo so the AHA-120 shouldn’t be seen as something rooted to the desktop.
Battery
In fact, the AHA-120 carries a huge 4.2amp lithium battery in the housing to power the unique class A amplification circuit and hence the size which gives it oodles of playtime without resorting to a charge.
Justin’s estimates run at around max 60 hours for 600ohms and 18 hours for 32 ohms which is really long to be honest, putting it in the much vaunted FiiO playback time for a far superior and weightier design which is fantastic.
I have yet to really see a Class A portable amp implemented like this, sure a few DIY interpretations from the hardcore but nothing this mature and market ready.
uHA-120 Design
The uHA-120 is an AB portable headphone amp that uses a push-pull circuit allowing the amp to switch between the “class A and the B” depending on the demands being put on the amp and is great for minimizing crossover distortion.
Though less efficient than class B it is certainly more efficient than class A amps such as the AHA-120 hence the smaller size and smaller battery but great playback time of around 24 hours.
Gain control in the u-HA-120 is adjustable with a quick opening of the casing and changing the gain jumpers on the PCB. The kit comes complete with a gain setting toolkit consisting of a hex key and battery tool and takes but a few mins to change to your desired setting with a max setting of 10db/6db possible on the jumper settings.
Features
Both amps come with the ability to play portable or through USB through a feature called APSS which is controlled through a white selector on the rear of each amp. APSS stands for Amplified Power Source Select and in a nutshell, it basically allows you to select a USB or battery as your power source depending on your needs.
Now interestingly this is not a benign feature designed to make the amps look sophisticated. The APSS does actively change how both the uHA-120 and AHA-120 sound by giving both amps a significant high voltage swing boost.
Those using higher impedance headphones or demanding tracks might appreciate this over the standard battery selector allowing the necessary power to drive those demanding cans without risking distortion creep or losing any dynamics in their playback.
AHA-120 Differences
The AHA-120 further differentiates itself from its smaller sibling with a front plate impedance selector dial allowing you to select impedance levels from 32ohms to 600ohms to get the most out of your headphone demands and of course depending on what genre of music you are driving it with.
The AHA-120 also comes complete with a really nice high-end Vishay volume potentiometer which is a custom-made high-spec pot from France (hence Vishay right?) that specifies a tighter channel tracking over the standard volume control pot.
The resistance and turn of the pot are very silky smooth indeed and very accurate. I have tried a fair few in my time and this one really exudes confidence in its level of control.
uHA-120 Differences
The uHA-120 front fascia is a bit more simple lacking in the impedance selector of the AHA-120 and the Vishay pot but the “white velvet” pot is the first resistance type based on/off pot I have used and I am quite impressed with its implementation.
Rather than a clunky on and off you simply push through a small resistance barrier and it is on. It won’t turn on by accident due to the level of resistance but the functionality is very smooth indeed. It’s quiet, very quiet and you only really know it’s on with a combination of LED lights coming on and the resistance in the pot weakening.
Both amps have rear charge rate selectors through which you can choose between a fast and normal setting. In most cases, the fast setting for USB should suffice but those with slower USB outlets might prefer the normal setting due to the reduced power of these settings.
Sound Impressions
In short, one is more musical and the other is more neutral but still, both have a fairly thick audio signature that I am going to presume now is the house sound of Just Audio.
Both convey a more analog feel to their playback but both with their own distinct signatures. They are pretty balanced overall in their approach but the uHA-120 is the musical brother with a more pronounced tuning for bass impact than the more neutral AHA-120.
That is not to say the uHA-120 is in any way muddied or attenuated. The mids on the uHA-120 are excellent, clear, and detailed. The bass is tight, and impactful rather than sloppy and works exceedingly well with beat-centric genres that add a bit of extra oomph to some heavy rock that I am rather fond of.
Synergy
Anyone who knows me knows my love of the K550 headphone this year. One of the most articulate and responsive closed-back headphones and a marked improvement on the thin and incoherent K series.
AKG K550
Well, the u-HA-120 takes up the K550 enjoyment a big notch. AKG is famous for their frugal bass tuning in all but a few of their headphones and the K550 is no exception though certainly better than the K701/2.
The uHA-120 adores the K550 bringing in a more pronounced bass emphasis and rounded more natural feel to the highs. The K550’s slightly sparky nature is somewhat tamed with the uHA-120’s balanced reproduction and the bass extension leaps up a notch or two also.
AKG K501
So I got a bit braver and threw the K501 into the mix also. A notoriously hard-to-drive headphone with glorious mids and below-average bass extension if underpowered.
The results were almost as good as the K550. Still slightly thinner the pot was up to about 1-2 pm on the dial but the mids were just glorious as always.
Slightly less bass oomph but honestly was not surprised as anything short of a full desktop can get the absolute best out of the K550 but very impressive indeed. Everything was snappy, clean, and very transparent and plenty of sound stage. A bit of a result there I think.
Audeze LCD-2
The biggest surprise of all was how it handled the LCD-2 rev 2. Very impressive is the short answer. The uHA-120’s power should not be underestimated for its size.
The LCD-2 is not the hardest planer to drive on the market but it does need some power to shine and reproduce that slam it is so famous for. To its credit, the uHA-120 did a fantastic job of ensuring the slam strayed right on cue without losing that wonderful mid-section of the LCD-2 either.
If there is one thing though the uHA-120 can’t quite achieve which its bigger brother has and that is the sound stage. Just losing out to the AHA-120 in terms of the expansive sound stage.
If you want an amp with a dirty club feel, aggressive bass tuning, and a wonderfully transparent and lush mid-section then the uHA-120 is the ticket. Honestly, the gain on this is ridiculous for its size and capability.
So onto the AHA-120 and just because it is bigger I did say don’t expect a bigger bass monster or musical version x 2 of the uHA-120.
The AHA-120 takes us in a different direction. That Class A amp is something special and the upgrade in resolution and detail and sound stage is immediately noticeable with the LCD-2 Rev 2.
Working that Vishay pot to around 12 noon is sufficient for all but the most tone deaf to be honest so no question it has the power also for the LCD-2 rev 2.
It does not have the aggressive bass punch of the uHA-120 but it has a more detailed flowing reproduction with a much more expansive sound stage. Compared with the iBasso Pb2 which is a 26v swing and very powerful amp I found the AHA-120 to offer a richer and fuller sound that was much more enjoyable and musical than the colder thinner Ibasso signature.
It lacks the coloration of the ALO Audio range such as the National or Continental so it is not going to leap out at you but what you do get is a very competitive transparent and versatile amp that works wonderfully well with a ton of genres.
Our Verdict
These are special amps.
Understated as they look they punch hugely above their portable or transportable weight. If you are veering to bass and want a very portable setup grab the uHA-120 and if you want something a bit more detailed and resolving then the AHA-120 is going to cover a lot of genres very well indeed for the demanding audiophile.
The balanced setup of both amps makes them very likable indeed. The playback time is way above the industry average. A lot of thought has been put into these amps by Just Audio and a lot of high-grade materials are used in the process of manufacturing them also.
I like it when a manufacturer doesn’t compromise on the build and quality of materials used and the price is well worth it. Both can driver planers with ease – there was a time when that was out of the question, and still is for most portable amps to be honest.
More info on these can be found at: www.justaudio.co.uk
That’s it, I am done for Xmas, outta here, and have a great one guys! See you in the new year!!
Just Audio AHA-120 Specifications
- 60 mWrms/channel into a 32 ohm @ nominal (3.6V) battery voltage
- 10 mWrms/channel into a 300-ohm load @ nominal battery voltage
- 16 mWrms/channel into a 300-ohm load @ fully charged (4.2V) battery voltage
- 28 mWrms/channel into a 300-ohm load with a 5.2V USB power supply
- Distortion (THD): <0.002% @ 1KHz (11dBu output level, with both channels driven with 32 Ohm headphones) Dynamic range (dBA): >100dB
- Bandwidth (-1dB): 10Hz-40kHz
- Output impedance: < 3 ohm
- Output current limit: +/-250mA per channel
- Maximum Gain: 12dB
- Channel balance: <1.5dB (over entire electrical travel of volume setting)
- Battery recharge time (max): 9-hour fast charge; 21-hour normal charge
- Dimensions(approx): height: 26mm, width: 80mm, length: 126mm
- Weight: 332g +/-1g
Just Audio uHA-120 Specifications
- 60 mWrms/channel into a 32 ohm @ nominal (3.6V) battery voltage
- 10 mWrms/channel into a 300-ohm load @ nominal battery voltage
- 16 mWrms/channel into a 300-ohm load @ fully charged (4.2V) battery voltage
- 28 mWrms/channel into a 300-ohm load with a 5.2V USB power supply
- Distortion (THD): <0.005% @ 1KHz (-20dBu to 5dBu output level, with both channels driven with 32 Ohm headphones) Dynamic range (dBA): >100dB
- Bandwidth (-1dB): 12Hz-40kHz
- Output impedance: < 1ohm
- Output current limit: +/-80mA per channel
- Maximum Gain:(REV B): 10dB/6dB (Jumper selectable)
- Battery recharge time (max): 2.5-hour fast charge; 6-hour normal charge
- Dimensions (approx): height: 23mm, width: 52mm, length: 85mm
- Weight: 125g +/-1g
