FLUX FCN-10 Review

Power and finesse

Pros: + Reference sound performance
+ Excellent as a standalone DAC
+ Excellent as a standalone amplifier
+ Excellent as a combo unit
+ Power house
+ Discrete RPi streamer included
+ Stepped attenuator
+ Silent
+ Sturdy build quality
+ 4 pin XLR output embedded

Cons: – No coaxial input
– A variable line out could be useful
– Old school appearance

The Flux Lab Acoustics FCN-10 was kindly loaned for the purpose of this review.
This is my honest and subjective evaluation of it.
All links provided are not affiliated and I don’t earn anything by clicking on them.
You can buy it directly from their website.
https://fluxlab-acoustics.com/product/fcn-10/

Introduction

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 pure headphone amplifiers and dac / amp combos, some of them with streaming capabilities.

FCN-10 Technical parameters

The FCN-10 is a streamer DAC with a full scale fixed analog output and a pure class A headphone amplifier.
There are two variants available , the FC-10 with a second USB 2.0 port and the FCN-10 without it but with an added extra built-in 2.4GHz WiFi receiver.

The FCN-10 is a modern combo device for sophisticated owners of high-quality, demanding headphones. It combines a high quality DAC, a streamer and exactly the same class A powerful amplification circuit design as in the much acclaimed FA-10 amplifier.
This is not the usual do it all in one device but rather a combination of three different and discrete high end components.
A high-quality implementation of the digital board and interfaces, combined with the amplifier enclosed in a classic design compact chassis.

So if we have a look at the inside we can identify the three main boards powered by a large custom made – low noise – toroidal transformer with separate linear regulated power supplies for all the critical digital and analog circuits.

The transformer and the power PCB are isolated inside an extra department with a thick metal wall so that they don’t interfere with the rest of the boards.
Unfortunately the streamer board is housed inside the same compartment but to be honest we haven’t detected any noise attributed to it.

The digital to analog converter is built around two AKM AK4493 DAC chips that they work in a dual mono configuration in order to squeeze out 3dB more of dynamic range and better crosstalk.
This is not a balanced design and the two DAC chips are used together in order to provide the best available performance at the single ended output.
The analog outputs of the DAC and the headphone amplifier are single ended and the 4-pin XLR jack is there for convenience only in order to accommodate balanced cables without the need of an adapter.

The USB receiver is from Amanero combined with three different clocks and the unit supports LAN input, up to 384 kHz sampling and up to 32-bit, DSD64, DSD128 , USB 2.0 input, up to 384 kHz sampling and up to 32-bit, DSD64, DSD128, DSD256 (Win only), DSD512 (Win only).
The FCN-10 digital inputs are LAN , PC USB input / USB 2.0 for external drives and 2.4 GHz WiFi with an external antenna while the FC-10 ditches the WiFi for an extra USB 2.0 input.
Sadly a coaxial input is not available so we couldn’t use our CD transport.

The streaming service is not handled by a generic IC as is the common case with most of all in one streamers but rather is well implemented with a discrete RPi computer board that runs under the moOde OS.
If we open the chassis we can easily spot the micro SD card and then we can burn a different OS of our preference.

The amplifier circuit used is essentially the same as the FA-10 or if you prefer the FCN-10 is the FA-10 with an added DAC and a streamer board above it.
This is one of the most powerful amplifiers in the market with the huge power output of 16 Watt into 32Ω loads.
We can even run easy speakers with it!
The amplifier circuits are employing J-Fet input stages and high power Toshiba bipolar transistors at class A mode with a supply voltage of 80 volts of output stage.

High transparency at any volume level and absence of even minimal unbalance of the channels, allows you to more accurately set the volume level thanks to 64-step relay volume control attenuator.
Three GAIN modes give you unique flexibility to use the amplifier with a wide range of headphones without loss of sound performance quality.
Large rectifier capacitance is used for best performance with a total of 4×6800μF capacitors.

All the components that are employed inside the unit are of high quality and only from well established brands.

Build quality and layout

The unit is housed inside a simple metal chassis with only the faceplate being made from CNC milled high quality aluminum.
The overall design is quite ordinary and outdated with a clean and simple look that minimalists should love but others might hate.
The dimensions are 46x42x18cm and the weight is a whole 6.6kg.

At the middle of the front face we have the volume pot while at the right we get single ended and balanced XLR headphone outputs and at the left side three simple small and rather uninspiring switches.
One is for on/off duties , the other one to select input between AUX – USB – LAN and the third one for gain control between high/medium/low.
At the back lies the iec plug , the wireless antenna , the USB 2.0 and LAN inputs , the AUX RCA input and the DAC RCA output.
All the used plugs are of good quality.

Operation

Operation is very simple and we can choose to run the unit as a stand alone DAC or as a separate headphone amplifier from the AUX input or as a combo DAC/amp unit.
For digital input we can use either the LAN or the WiFi or the PC USB input or even plug an external hard/flash drive at the available USB 2.0 ports.
Under PC USB DAC mode the operation is the usual one but if we opt for the LAN/WiFi/USB 2.0 input then it gets a little more complicated.

We must have knowledge of RPi and moOde OS in order to operate the streamer or play files from an external drive.
Surprisingly there is no manual included inside the box and even more surprisingly not an online tutorial at the Fluxlab Acoustics website.
The user must contact the Fluxlab support to ask for a tutorial or search online to find an available one.
Thankfully there are quite a few comprehensive ones and with a little reading and a small learning curve we can finally run the steamer with an app like the BubbleUPnP.
So after we master the moOde OS then we can easily have access to online streaming services , free webradios , our local network and play music from external hard/flash drives.

Sound quality

Since the FCN-10 is essentially a separate DAC and a headphone amplifier supporting single or combined use we are going to split the sound impressions into three parts.

Headphone Amplifier

We fed the amplifier with various external Dacs from the high end Denafrips Venus mkii to the Cambridge Audio 851N or even the entry level SMSL M100 mkii.

The amplifier plain and simple is a truly excellent performer without any downsides.
It is ultra linear and flat with a great transparency to it while it poses very musical characteristics without altering the frequency response.
It is a class A full bodied presentation from top to bottom adding great substance to the notes that sound perfectly natural with lifelike timbre.
Bass is thick and very controlled with extra astounding dynamics while maintaining excellent layering and definition.
The amplifier is such a powerful beast that can drive every available headphone at the market without even sweating with the ability to respond instantly and lightning fast from silence to powerful outbursts and vice versa.
Mids and highs are crystal clear and detailed, full of energy and still full bodied.
Everything is under control and balanced with a smooth and easy going nature without any hint of extension loss.
Despite being uber powerful the amplifier is surprisingly silent even with higher sensitivity headphones.
The silent background adds greatly to the transparency and helps all the fine nuances to emerge and integrate with the whole.
The soundscape is very holographic offering combined depth and width with pinpoint accuracy making for a very persuasive and lifelike rendering of the recording venue.
The stepped volume attenuator performs miracles regarding channel imbalance and fine control while the gain switch is very useful and allows full pot use even with very sensitive headphones.
With all the headphones at our disposal we didn’t need to reach for the high gain.
A performance par excellence and we certainly would recommend the FCN-10 for the amplifier section only.
Fortunately users that need a separate amplifier can buy the FA-10 for a lower price with the exact same performance.

Standalone DAC

The DAC section retains more or less the same sound characteristics.
It is neutral and balanced with a great emotional depth and an R2R kind of flavor to it.
We have heard a lot of AK4493 implementations but this is one of the best with excellent extension to both ends and ample dynamics.
It is a full bodied and well controlled sound that can do justice to all musical genres.
Bass is deep and controlled well defined and detailed while the mid region clarity is very good.
The notes are rounded and engaging with linear transition to the higher register that is still smooth but very detailed and full of energy.
Timbre is natural and the DAC can draw a well proportioned picture of the recording.
The FCN-10 DAC section can easily stand strong against the competition and be used as a standalone DAC with external headphone or speaker amplifiers.
We would like to have a variable line output in order to use the FCN-10 with active speakers but we perfectly understand Flux Labs ditching it for a purist approach.

Amplifier and DAC combined

Not much left to talk about here because as you can very easily understand the combination of the two great performers results in an awesome combo unit with an upgraded performance to match.
The FCN-10 is an excellent standalone DAC and amplifier but when combined the result is a heavenly experience.
This is the most powerful DAC/amp unit in the market with truly exceptional performance and you will be hard pressed to find something better at this price point.
And we are not talking only sheer power but rather pure musical enjoyment with every headphone that you can think of.

At the end

The Fluxlab Acoustics FCN-10 is easily the most powerful DAC/amp/streamer in the market.
But power is useless without quality and this unit it sure delivers in spades.
Excellent as a headphone amplifier/DAC combination the FCN-10 is equally competent as a standalone DAC making for a multi talented device to form the centerpiece of a combined headphone and speakers system.
Consider the extra embedded high quality streamer as a free bonus.
The FCN-10 simply put it, is one of the best high end multi purpose headphone systems in the market right now that can easily count as an end game piece of gear.

Test playlist – http://open.qobuz.com/playlist/5669033

Copyright – Petros Laskis 2021