Just Audio


portable Class A Headphone Amp

© Just Audio Ltd.

Product Description

The AHA-120 is a portable pure class A headphone amplifier, suited to driving most full size headphones and IEMs.
Intended for the most discerning listener, the AHA-120 incorporates a discrete class A output stage, whilst the front panel features an additional high quality NKK rotary selector, enabling the end user to select the optimum amount of class A bias for a given headphone impedance. This feature extends operating time when using higher impedance headphones; and even when using the most class A bias, the high capacity internal rechargeable battery still enables up to 20 hours[1] of operation.
Like the µHA-120, micro jumpers are fitted to the PCB as standard, so that the AHA-120 can be configured to either 6dB (x2) or 12dB (x4) maximum gain to suit headphones and IEMs[2]. In addition, the same careful attention has been placed on the layout and choice of the electronic components, with particular emphasis on ensuring the very best audio quality and excellent immunity from unwanted noise sources.  
As standard the stereo analog volume potentiometer is a specially in-house graded and modified part. This process involves only selecting parts with the best channel balance and then applying our ‘White Velvet’ modification, creating a near perfect passive analog volume control with a premium smooth and consistently weighted rotary movement.

Dec 2012:

headfonics logo

The clue is in the Name – Just Audio. Founded in the UK by Justin Harris in 2009 who has a first class Masters 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 lets start with the more emotional responses that I got from the meet before we do the nerd fest.
Just Audio amp’s 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 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.

Technical Specs:
60 mWrms/channel into 32 ohm @ nominal (3.6V) battery voltage
10 mWrms/channel into 300 ohm load @ nominal battery voltage
16 mWrms/channel into 300 ohm load @ fully charged (4.2V) battery voltage
28 mWrms/channel into 300 ohm load with 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