FLUX FA-12 Review

FLUX FA-12 Review

19 September 2021 0 By Petros Laskis

The Equilibrist

Pros: – Natural and organic timbre
– Inherently musical and warm
– Transparent
– Smooth and relaxed
– Technically refined
– Powerful
– Three gain settings
– True balanced
– 64-step relay volume control attenuator
– Only premium components

Cons: – Can be used either balanced or single ended only
– Could do with a little more dynamics
– Not full aluminium construction

This review is dedicated to the suffering people of Ukraine with the wish for the war to end as soon as possible.

The Flux Lab Acoustics FA-12 and FCN-10 were kindly loaned for the purpose of this review and this is my honest and subjective evaluation.
All links provided are not affiliated and I don’t earn anything by clicking on them.
You can buy directly from their website


Flux Lab Acoustics is a Ukrainian company dedicated to the design and manufacturing of high-end audio products.
Fully designed and manufactured in Ukraine.
Flux Lab Acoustics is devoted to developing best-sounding audio equipment.

They have an unrivaled experience in the high-end audio industry covering both digital & analog board design, software developing as well as mechanical design.
The company strongly believes that correctly applied technology confirmed by in-depth measurements at the lab and finally a thorough listening is the way to improve the art of audio reproduction.

They produce headphone amplifiers and dac / amp combos with embedded streaming capabilities.
Their current flagship is the Volot a Dual Mono Class A headphone amplifier.

Technical specifications

The FA-12 is the only true balanced headphone amplifier from Flux Labs designed to deliver a warm, engaging character of the sound for the most sophisticated listeners.
In order to achieve this they have utilized a JFET input stage to drive the MOSFET output stage in a fully balanced topology without any kind of conversion along the signal path.


A large 60W toroidal transformer, wound in house, is feeding the linear power supply with a total filtering capacity of 60000μF, featuring separate regulations for all critical parts of the circuit.
The transformer with the first filtering stage board is housed at the left side of the chassis where it is isolated by the means of a large metallic bar in order to protect the main board from electromagnetic interference.


There is a 64-step relay volume control attenuator for precise adjustment and excellent channel matching even at the lowest setting.


All components used are top quality and they are sourced from famous brands such as Nichicon, TAKMAN, NIPPON, FUJITSU-TAKAMISAWA etc.


The rated power output is 300Ohm: 360mW RMS per channel (balanced mode), 32Ohm: 2600mW RMS per channel (balanced mode), 50Ohm: 1700mW RMS per channel (balanced mode).

Build quality and layout

The unit is a full desktop size measuring 46×42×18 cm with a substantial weight of 6.6kg.
The appearance is rather minimal and old school, someone might call it dull.
The left side is occupied by three simple switches for on/off – input selection between single ended/balanced – three gain settings (low/mid/high).
At the middle there is a high quality aluminium volume knob with good feedback and rotation while at the right part there are the two headphone outputs (6.35mm and 4-pin XLR).
At the backside there is the power plug followed by the RCA and XLR analog inputs.
All plugs are heavy duty and of high quality.
The front face plate is CNC milled aluminium and can be ordered into seven different colors while the rest of the chassis is made from a rather thin, black painted metal sheet.


Sound impressions

The FA-12 can be used either in single ended in/out or balanced in/out mode with the combination not being possible.
We can have both analog inputs plugged together but when we select the balanced in, the amplifier will output only the balanced signal and vice versa.
Great from a technical point of view but not very practical.
When using the single ended mode then we are practically utilizing half of the amp circuit.
Since FA-12 is a fully balanced design, our opinion is that buying makes greater sense only if we plan to use the fully balanced circuit.
For single ended only sources there are other great options within the Flux Labs brand, like the new FA-22 or the budget FA-12s and the powerhouse FA-10, where all outputs and inputs can be used in combination.


The main source of the listening tests was the Denafrips Ares II fed from the iFi ZEN Stream.
The Denafrips Ares II is an extended loan kindly provided from their EU official distributor www.denafrips.eu
We have used various headphones including the Sennheiser HD660s/650, HiFiMan Ananda, Focal Clear Mg, the HEDDphone and Meze Empyrean.

The FA-12 amplifier is not our first experience with Flux Labs since we have already tested the wonderful FCN-10 as you can read here
Both units share some common characteristics and it is not that difficult for the listener to find out that there is a well thought philosophy regarding the sonic approach.
It is pretty obvious that Flux Labs team are well after an engaging and highly musical sound that focuses on texture qualities.
The FA-12 possesses that nice class A warmth that imbues sound with sentimental and emotional depth leading in a constant communication with the listener rather than a mechanical and monotonous amplification.
No, it has nothing to do with frequency fluctuations since this is an absolutely flat and linear measuring amplifier, it is more about the harmonics blending with fundamentals adding this pleasing analogue timbre.

This is a fairly balanced amplifier and we are not talking circuit design here but rather about sound characteristics and the way they are presented by FA-12.

Balanced as a little laid back but not too much, not too fast nor too slow, just in the middle, playing music in a calm and relaxed manner never lacking nerve when it is needed.

Balanced as highly resolving but not analytical, aided in the task by the dead silent background to reward the listener with all the necessary micro details without becoming obsessed with the duty.

Balanced also in the bass that is extended and full bodied but not too thick, tight and controlled but not clinical, dynamically contrasted but not overly hard hitting, also layered and very clean with excellent separation when the bass line becomes densely populated.


Mids stand out for the naturalness of the timbre and the finest articulation, qualities that extend well into the higher frequencies.
The high frequencies are again balanced as they sound smooth and fatigue free but without lacking in energy and extension.
Transients are neither too fast nor slow while timing is great and there is an excellent coherency throughout the whole frequency range when it comes to note weight and body.
The soundstage is fairly extended, quite deep, with accurate positioning and great sense of space.
The listener sits rather close to the performers enjoying the performance with an intimate view.
This doesn’t mean that the presentation isn’t suitable for large symphonic works on the contrary it never feels congested but the real treat is with medium sized and small ensembles.

Comparison with the FA-10

For the comparison we have used the FCN-10 with the analogue input which is essentially the same amp portion as the FA-10.

Both amplifiers share the same DNA and they sound immensely musical, engaging, with the same analogue timbre and organic texture.
And if the FA-12 is the well tempered, phlegmatic brother, then the FA-10 is the brutal, sanguine one.
The FA-10 is muscular, raw power unleashed, the bass sounds heavier, fuller, hitting with greater dynamics and impact pushing the drivers to their limits.
Mids textural quality and timbre is the same on both amps as is the smooth, fatigue free and extended treble response but transient attack is faster and snappier on the FA-10 while general presentation is weightier.
The soundstage on the FA-10 is slightly more expanded and the listener is moved a couple of seats back, it takes a little more time for the notes to reach him adding more reverb.
Depth is a touch more stressed and holography stands out as a little better making the FA-10 great for large scale works.
Another thing of note is that FA-12 is more silent with a considerably blacker background, making it more resolving, the master of micro detail and better suited for sensitive headphones.
Two excellent amplifiers that are both equally enjoyable, the one a little relaxed, sweeter, smoother and intimate and the other grander and agile, will suit different systems and preferences.


At the end

The Flux Labs FA-12 strikes the perfect balance between technical refinement and a smoothly musical presentation awarding the buyer with excellent performance at a moderate price.
Highly recommended you just have to sit back in your chair, choose your favorite headphone and forget about the amplifier.
Press play on the source and get lost into your beloved tracks, not forgetting to place the “do not disturb” sign at your doorknob.

Test playlist

Copyright – Laskis Petros 2021.