FLUX M-Field Class-A MOSFET headphone amplifier
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Flux Lab Acoustics
Flux Lab Acoustics is a “boutique” Ukrainian company dedicated to the design and manufacturing of high-end audio products. Flux Lab previous products, like the FA-10 and Volot headphone amplifiers, received an unanimous reception by the headphone community and are now considered as benchmarks.
After a long time of silence because of the violent Russian invasion into Ukraine, Flux Lab Acoustics resumed business and made a strong comeback by presenting a class leading solid-state headphone amplifier, the Mentor that has already been reviewed here.
Flux Lab M-Field
The Flux Lab M-Field is a powerful headphone amplifier that was developed together with the Mentor but was released a couple of months later. So it doesn't come as a surprise that these two amplifiers share some common characteristics. However they also have some notable differences both in their internal circuit and their sound profile.
Technical highlights
The M-FIELD model uses MOSFET transistors in the output stage, instead of bipolar, so it has its own unique sound signature as we are going to find later on. Now let's check the technical characteristics of the M-Field.
The Power Supply
The power supply of the M-Field might look of a simpler design than that of the Mentor, which uses two transformers instead of one, but it is certainly not. The sophisticated power supply uses a single power transformer specially designed for this amplifier model, which has separate windings for powering the right and left channels. This transformer is larger than the ones found in the Mentor, it has an advanced design and is much more expensive to produce. The power transformer has a very low dissipation field and noise that permits the amplifier circuit to function without any apparent hum, even when using high-sensitivity headphones.
The power supply also uses four high-capacity capacitors produced by Cornell Dubilier, which can provide dynamic and detailed sound. Flux Lab also uses an Ultra Pure Oxygen Free Copper (UP-OFC) power cable by Neotech from the AC inlet socket to the power transformer. This allows it to achieve a more focused sound in the low-frequency range and more punch in the mid/high range.
The Power Amplifier
The output stage operates in class A, which allows transmitting signals of small amplitude with the highest accuracy. The amplifier circuitry uses J-Fet transistors at the input and MOSFET transistors at the output. The power supply for the amplifier circuitry is as high as 70 volts to ensure uncompromising dynamic performance with the most demanding headphones on the market.
By refining the heat sink design, the amplifier circuitry is promptly prepared for utilization, and subsequently shares its greatest sound quality only after a mere 15 minutes of warming up. In addition, the heat sink is partially placed under some of the PCB components, which allows the amplifier circuitry to start up faster and provides better thermal stability for the entire circuitry.
High quality, Ohno monocrystalline copper (UP-OCC) cable is used at the output to allow the amplifier’s circuitry to unfold to its full potential without compromises.
The Volume Control
The volume control is based on a relay attenuator and contains 64 steps of fine adjustment. The control circuit uses Panasonic fast signal relays with low contact resistance. The analog signal is fed to the relay attenuator located next to the input sockets, and the ALPS variable potentiometer (Blue Velvet series) is used for control only. This arrangement allows the classic potentiometer to be used for volume control, with the analog signal going to a relay control located next to the input jacks. This allows for high sonic transparency even at low volumes. The M-Field features an enhanced volume control program for better system response and improved overall usability. This volume control eliminates the problem of volume imbalance between channels and enables to finely tune the level even on high-sensitive headphones.
Electronic components and PCB
Flux Lab uses only high quality components for making the M-Field, like Takman resistors (Rex series), PRP resistors, Cornell Dubilier, Nichicon, Wima, and Epcos capacitors etc. You don't have to be an electronic engineer to admire how well assembled the internal circuit is, the PCB looks like a fine piece of art.
The Mono input module
The M-Field features the unique mono input module that was introduced with the Mentor and allows the synchronization of two amplifier units in a dual-mono mode for an even greater power output. When two M-Fields are connected in dual-mono mode, each channel of the amplifier operates in a fully balanced mode. You simply select which unit is the master and which is the slave. The synchronization system also allows you to control the operation of the second amplifier, so that when the master unit is switched on, the second unit is also automatically switched on. Flux Lab guarantees complete adherence, including the tone of the front panel, only when the two units are bought together.
The optional remote control
You can conveniently adjust and mute the volume of the M-Field with the aid of the remote control which is available as an optional purchase. You have the option to choose between a $15 plastic or a $50 full aluminum remote control. The latter might be a little expensive but it is a high quality and durable remote control crafted from CNC machined aluminum with a black anodized finish. A stylish and minimalistic remote control that matches well with the appearance of the amplifier.
The remote is not included as a standard to keep costs low and save some money for people who intend to use the M-Field in a desktop scenario. Since the volume controller is a relay stepped attenuator you are not going to see the volume knob rotate during adjustment but every time you touch the knob, the volume automatically reverts to its given position.
Power cable upgrade
Flux Lab suggests using a high quality power cable in order to enhance the audio performance of the M-Field. Actually they sell their own custom-made cable which is based on the NEP-5002 conductor from Neotech. The cable features thick conductors (0.42mm) of ultra-pure oxygen-free copper (UP-OFC). The ground conductor’s smaller cross-section (1.43mm) results in a slim and flexible cable for a better user experience. The cable provides complete protection from external electromagnetic radiation, thanks to an internal aluminum foil shield and a drain wire. Filling the free volume with synthetic fiber ensures comfortable flexibility and a “memory” effect, allowing the cable to be easily positioned and maintained in the desired position.
Each cable is hand-crafted and equipped with high-quality Viborg or Supra mains plug connectors with gold-plated brass and copper contact groups. The cable is supplied in a length of 1.8 meters (6 feet). You can select one of the available configuration options at the product page during check out. The cable with the Supra plugs will cost you $95 and $130 with the Viborg ones.
Non Audio stuff
The M-Field is identical looking with the Mentor, the only way to tell them apart is from the aluminum volume control knob which is of a slightly different design. Both of them look unique and stylish, it is difficult to decide which one is the most appealing, subjectively speaking I prefer that of the M-Field.
The front face of the M-Field is a solid, thick plate of CNC machined aluminum with an anodized smooth finish while the rest of the chassis is made from plain steel sheet with a black painting. The faceplate is available in coal black and titanium gray colors. Four anti-vibration feet are factory attached at the bottom of the chassis to ensure stability and vibration control.
The M-Field weights 6kg and measures 342x397x82mm thus making it more deep and less wide than the industry standard so you might have a problem placing it above or underneath other audio components.
The Flux Lab M-Field is a pure headphone amplifier without a preamplifier function or a digital section. It features both balanced XLR and single ended RCA line inputs that are located at the back of the unit. You can have them simultaneously plugged in and select the desired one from the corresponding switch at the front. The back also houses the AC input and the synchronization interface.
The minimalist looking front panel has power on/off, input and gain switches located at the left, the dominating volume control knob at the middle and two headphone outputs at the right. The first is a combined 6.35mm jack and 3-pin XLR for the mono mode while the second is a 4-pin XLR plug.
Power output and noise
The power output of a single M-Field is 9.6W (32Ω) and 1.6W (300Ω) per channel making it one of the most powerful headphone amplifiers in existence, albeit slightly less powerful than the Mentor.
A dual mono M-Field stuck will produce 26.1W (32Ω) and 5.1W (300Ω) per channel, an enormous amount of power that can drive with ease every headphone in existence. But it is not only about more power because a dual M-Field set-up will produce upgraded sonic performance and mainly better separation and imaging, larger soundstage and greater dynamics.
The amplifier has three gain settings (low, medium and high) for better matching with various loads. You can select the desired gain from the corresponding switch at the front panel. Output impedance is also very low (0.1Ω) so it can drive low impedance loads, even sensitive earphones because it has a low noise floor. Pretty amazing if you consider how powerful it is.
The relay attenuator adjusts the volume in 1.5dB increments with a total of 64 steps so you can do fine adjustments without getting loud too fast. The M-Field can drive the Hifiman Susvara at just 40-50 steps of the medium gain setting. The only part of the M-Field that gets mildly warm, even under stress conditions, is the back side of the bottom so it will not be a problem to place it in a poorly ventilated area like a shelf.
Audio stuff
Have you ever dreamed about getting yourself a tube amplifier but you were always hesitant to do it because you were afraid to mess with tubes and their associated hassle and potential drawbacks? Well, now you can experience some of the so-called tube magic without buying a tube amplifier. How is that possible? Just get the Flux Lab M-Field, a solid state amplifier that sounds surprisingly tube-like without involving any tubes.
MOSFETs have always had this unique ability to replicate tube sound when properly implemented and in the case of the M-Field we are talking about genius engineering not imagined before at this price point. The M-Field is soulful and musical, its sound is exceptionally real and alive, the music has a natural flow that simulates the senses of the listener in a way that only the best tube amplifiers can do.
The M-Field is immersive and holographic, it produces natural and organic timbres with the most colorful harmonies that have a rich saturation reminiscent of tubes but without the usually associated negatives, like background noise, haziness, bloom or lack of control. Someone will usually have to buy an expensive tube amplifier to get rid of these negatives. The truth is that no solid-state amplifier can match a high-end tube amplifier but the M-Field can get you very close without involving any tubes or having to spend a fortune.
The M-Field is slightly warm and smooth but not dark sounding. The mid-range especially, is expressive, articulate, musical and engaging with impressive timbre quality. The sound is organic and analog-like, instruments and voices sound eerily lifelike with exceptional tonal accuracy. No op-amp artificiality, no fakeness or sterility, no metallic sheen or harsh treble. Rest assured that the M-Field is just like a musical instrument that plays music with all its realism and sentimental depth.
Technicalities
Like said, the M-Field can get you very close to high quality tube sound and at the same time is as technically proficient as the best solid-state amplifiers.
The Flux Lab M-Field ideally combines stunning musicality with supreme fidelity and transparency. Frequency response is flat and linear, the M-Field doesn't use any kind of bass boosting, treble recession or any other kind of frequency response manipulation tricks to shape the sound. The amplifier has excellent technicalities and precision close to that of the Mentor. Don't think that its warm and inviting character is going to alter the frequency response of your headphones. Bright headphones will still sound bright and warm will remain warm.
A few notes about matching
The M-Field is a good match for brighter and lean sounding headphones not because it lowers their treble amplitude like an equalizer but because it doesn't highlight their brightness and strengthens their lean nature by adding the missing weight and fortifying the bass. Some of you might think that warm and thick sounding headphones are not going to pair well with the M-Field but this is far from the truth or at least I didn't have any problem enjoying the Meze Empyrean which didn't sound that thicker or warmer because the stellar technicalities and transparency of the M-Field counterbalanced its other characteristics.
In a similar fashion, the M-Field proved equally at home with more technical D/S DACs as well as with more musical and analog sounding sources like the Laiv Harmony DAC.
More Audio stuff
The bass is full bodied and weighty, visceral and thick with exceptional layering and definition. You can easily follow the most populated bass lines and easily discern between the faintest notes, nuanced pluckings or gentle bowings on the strings, staccato or legato passages. Deep and impactful with realistic dynamic swings, the bass also perfectly captures the natural reverb of the recording hall. It is elastic but not loose, far from sounding dry or lean and at the same time is tight and as fast as the music demands. The amplifier is very dynamic and powerful but it doesn't throw the bass at the listener's face, as it perfectly harmonizes with the rest of the frequencies without drawing attention to itself or causing low-end fatigue.
The treble might be relatively smooth, mildly forgiving and devoid of any sharpness but at the same time it has plenty of energy and light, as well as extension and sparkle to avoid darkness or sluggishness while staying polite. Detail retrieval and resolution are stellar but not class leading as in the case of Mentor. The M-Field is tuned on purpose to sound less analytical and magnifying than its brother, a different kind of approach that focuses on intimacy and increased musicality rather than absolute technicalities and resolution.
The soundstage is rather unique in its presentation, not as expanded and big as in the Mentor but with amazing spaciousness despite its relatively compact size. The overall feeling is quite intimate, the listener feels like sitting closer to the performers but at the same time the depth layering is so impressive that you never experience the music as a wall of sound despite the proximity to the stage. The soundstage is extra holographic and immersive with excellent separation between individual performers and different blocks of instruments while you can always perceive the ambient information as captured in the recording.
Comparison with the Flux Lab Mentor
Some differences regarding the sonic presentation between the Flux Lab M-Field and the Mentor were described in the main course of the review but let's summarize them. Except for being slightly more powerful, the Mentor is the natural leader when it comes to transparency and overall technicalities without sacrificing much musicality. The Mentor is undeniably more dynamic and impactful, the M-Field sounds a bit softer in comparison but it has more weighty and visceral textures. The bass on the M-Field sounds fuller and more elastic with greater amounts of reverberation, it is less dry than the Mentor but the latter takes the lead when it comes to control, layering, definition and the complexity of the textures structure while it is more accurate and precise.
The Mentor is musical and engaging in its own right but it can't match the tube-like character of the M-Field which is more organic and soulful in comparison, with slightly more natural timbre and saturated harmonies. The M-Field sounds warmer, more expressive on the mid-range and smoother on the treble but the Mentor outclasses it in resolution, refinement and the quality of the textures.
The soundstage of the Mentor is larger and bigger than the M-Field, with notably better separation and class leading imaging. The M-Field is more intimate but also more holographic, however the Mentor offers a grand hall listening experience.
The Mentor has class leading neutrality, fidelity and transparency without lacking in musicality and engagement but the M-Field is undeniably one of the most musical, natural and organic sounding solid-state amplifiers ever made.
Comparison with the Aune S17 Pro
The humble Aune S17 Pro is maybe the best solid-state headphone amplifier under $1K for anyone who values musicality and timbre realism above anything else. Just like the M-Field, the Aune S17 Pro is an amplifier with a tube-like sound character while having a good level of solid-state technicalities. The M-Field is the S17 Pro on steroids, it takes from where the Aune has left and improves merely everything. From timbre realism to the quality of the textures, transparency, definition, resolution, clarity and all technicalities. If you own and love the Aune S17 Pro, then think of the Flux Lab M-Field as the natural upgrade path you have been dreaming about.
Comparison with various Violectric amplifiers
The Flux Lab M-Field is more musical and tube-like sounding than every Violectric amplifier I can think of. It's more visceral and weighty, slightly warmer and more soulful with an overall technical performance somewhere between the V222 and the V330 but can't reach the V550 which is only comparable with the Mentor.
Comparison with the Cen.Grand 9i-906
A rather unfair comparison as the Cen.Grand 9i-906 retails for $4190 so it will not sound too odd if you read that this amplifier successfully combines the best characteristics of the M-Field and the Mentor. However, it doesn't have the personality of the M-Field, not of the Mentor, which both have their own unique sound character that many people will prefer over the Cen.Grand 9i-906. Additionally let's not forget that the Cen.Grand is out of reach for most people out there when both the M-Field and the Mentor are affordable and some of the best bargains in the audio industry.
Conclusion
The Flux Lab M-Field and the Mentor are like variations on the same musical theme and people familiar with music synthesis will definitely know how difficult it is to write inspired variations of the same theme.
I could end this review by just copying the conclusion of the Mentor review and replacing the word “Mentor” with “M-Field”. It would read like this:
“With the introduction of the Flux Lab M-Field, high-end quality has become more affordable than ever before. Undoubtedly, the Flux Lab M-Field reigns as the most cost-effective high-end headphone amplifier available, featuring outstanding value for money and securing its position as one of the top bargains in the audio industry.”
Flux Lab Acoustics has cleverly made two high-end headphone amplifiers with slightly different sound signatures in order to cater for the two larger audiophile groups. The ones who desire the best possible technical performance but are not willing to sacrifice much musicality and the others who most value unparalleled musicality but are not willing to skip on technicalities. Whether you belong to the first or the second group, Flux Lab Acoustics have you covered and without the need to spend a fortune. Be it the M-Field or the Mentor, rest assured that you are buying an exceptional high-end headphone amplifier at an unbeatable price.
The review sample was kindly provided free of charge in exchange for an honest review.
The price of a single M-Field is $1299 and you can buy it from Flux Lab online shop. You can take advantage of the pre-sale offer price which is $1199. The amplifier ships from the EU so buyers within the EU zone will not have to pay import fees and tax. The M-Field is currently in production and will be available for sale very soon.
Flux Lab Acoustics is a “boutique” Ukrainian company dedicated to the design and manufacturing of high-end audio products. Flux Lab previous products, like the FA-10 and Volot headphone amplifiers, received an unanimous reception by the headphone community and are now considered as benchmarks.
After a long time of silence because of the violent Russian invasion into Ukraine, Flux Lab Acoustics resumed business and made a strong comeback by presenting a class leading solid-state headphone amplifier, the Mentor that has already been reviewed here.
Flux Lab M-Field
The Flux Lab M-Field is a powerful headphone amplifier that was developed together with the Mentor but was released a couple of months later. So it doesn't come as a surprise that these two amplifiers share some common characteristics. However they also have some notable differences both in their internal circuit and their sound profile.
Technical highlights
The M-FIELD model uses MOSFET transistors in the output stage, instead of bipolar, so it has its own unique sound signature as we are going to find later on. Now let's check the technical characteristics of the M-Field.
The Power Supply
The power supply of the M-Field might look of a simpler design than that of the Mentor, which uses two transformers instead of one, but it is certainly not. The sophisticated power supply uses a single power transformer specially designed for this amplifier model, which has separate windings for powering the right and left channels. This transformer is larger than the ones found in the Mentor, it has an advanced design and is much more expensive to produce. The power transformer has a very low dissipation field and noise that permits the amplifier circuit to function without any apparent hum, even when using high-sensitivity headphones.
The power supply also uses four high-capacity capacitors produced by Cornell Dubilier, which can provide dynamic and detailed sound. Flux Lab also uses an Ultra Pure Oxygen Free Copper (UP-OFC) power cable by Neotech from the AC inlet socket to the power transformer. This allows it to achieve a more focused sound in the low-frequency range and more punch in the mid/high range.
The Power Amplifier
The output stage operates in class A, which allows transmitting signals of small amplitude with the highest accuracy. The amplifier circuitry uses J-Fet transistors at the input and MOSFET transistors at the output. The power supply for the amplifier circuitry is as high as 70 volts to ensure uncompromising dynamic performance with the most demanding headphones on the market.
By refining the heat sink design, the amplifier circuitry is promptly prepared for utilization, and subsequently shares its greatest sound quality only after a mere 15 minutes of warming up. In addition, the heat sink is partially placed under some of the PCB components, which allows the amplifier circuitry to start up faster and provides better thermal stability for the entire circuitry.
High quality, Ohno monocrystalline copper (UP-OCC) cable is used at the output to allow the amplifier’s circuitry to unfold to its full potential without compromises.
The Volume Control
The volume control is based on a relay attenuator and contains 64 steps of fine adjustment. The control circuit uses Panasonic fast signal relays with low contact resistance. The analog signal is fed to the relay attenuator located next to the input sockets, and the ALPS variable potentiometer (Blue Velvet series) is used for control only. This arrangement allows the classic potentiometer to be used for volume control, with the analog signal going to a relay control located next to the input jacks. This allows for high sonic transparency even at low volumes. The M-Field features an enhanced volume control program for better system response and improved overall usability. This volume control eliminates the problem of volume imbalance between channels and enables to finely tune the level even on high-sensitive headphones.
Electronic components and PCB
Flux Lab uses only high quality components for making the M-Field, like Takman resistors (Rex series), PRP resistors, Cornell Dubilier, Nichicon, Wima, and Epcos capacitors etc. You don't have to be an electronic engineer to admire how well assembled the internal circuit is, the PCB looks like a fine piece of art.
The Mono input module
The M-Field features the unique mono input module that was introduced with the Mentor and allows the synchronization of two amplifier units in a dual-mono mode for an even greater power output. When two M-Fields are connected in dual-mono mode, each channel of the amplifier operates in a fully balanced mode. You simply select which unit is the master and which is the slave. The synchronization system also allows you to control the operation of the second amplifier, so that when the master unit is switched on, the second unit is also automatically switched on. Flux Lab guarantees complete adherence, including the tone of the front panel, only when the two units are bought together.
The optional remote control
You can conveniently adjust and mute the volume of the M-Field with the aid of the remote control which is available as an optional purchase. You have the option to choose between a $15 plastic or a $50 full aluminum remote control. The latter might be a little expensive but it is a high quality and durable remote control crafted from CNC machined aluminum with a black anodized finish. A stylish and minimalistic remote control that matches well with the appearance of the amplifier.
The remote is not included as a standard to keep costs low and save some money for people who intend to use the M-Field in a desktop scenario. Since the volume controller is a relay stepped attenuator you are not going to see the volume knob rotate during adjustment but every time you touch the knob, the volume automatically reverts to its given position.
Power cable upgrade
Flux Lab suggests using a high quality power cable in order to enhance the audio performance of the M-Field. Actually they sell their own custom-made cable which is based on the NEP-5002 conductor from Neotech. The cable features thick conductors (0.42mm) of ultra-pure oxygen-free copper (UP-OFC). The ground conductor’s smaller cross-section (1.43mm) results in a slim and flexible cable for a better user experience. The cable provides complete protection from external electromagnetic radiation, thanks to an internal aluminum foil shield and a drain wire. Filling the free volume with synthetic fiber ensures comfortable flexibility and a “memory” effect, allowing the cable to be easily positioned and maintained in the desired position.
Each cable is hand-crafted and equipped with high-quality Viborg or Supra mains plug connectors with gold-plated brass and copper contact groups. The cable is supplied in a length of 1.8 meters (6 feet). You can select one of the available configuration options at the product page during check out. The cable with the Supra plugs will cost you $95 and $130 with the Viborg ones.
Non Audio stuff
The M-Field is identical looking with the Mentor, the only way to tell them apart is from the aluminum volume control knob which is of a slightly different design. Both of them look unique and stylish, it is difficult to decide which one is the most appealing, subjectively speaking I prefer that of the M-Field.
The front face of the M-Field is a solid, thick plate of CNC machined aluminum with an anodized smooth finish while the rest of the chassis is made from plain steel sheet with a black painting. The faceplate is available in coal black and titanium gray colors. Four anti-vibration feet are factory attached at the bottom of the chassis to ensure stability and vibration control.
The M-Field weights 6kg and measures 342x397x82mm thus making it more deep and less wide than the industry standard so you might have a problem placing it above or underneath other audio components.
The Flux Lab M-Field is a pure headphone amplifier without a preamplifier function or a digital section. It features both balanced XLR and single ended RCA line inputs that are located at the back of the unit. You can have them simultaneously plugged in and select the desired one from the corresponding switch at the front. The back also houses the AC input and the synchronization interface.
The minimalist looking front panel has power on/off, input and gain switches located at the left, the dominating volume control knob at the middle and two headphone outputs at the right. The first is a combined 6.35mm jack and 3-pin XLR for the mono mode while the second is a 4-pin XLR plug.
Power output and noise
The power output of a single M-Field is 9.6W (32Ω) and 1.6W (300Ω) per channel making it one of the most powerful headphone amplifiers in existence, albeit slightly less powerful than the Mentor.
A dual mono M-Field stuck will produce 26.1W (32Ω) and 5.1W (300Ω) per channel, an enormous amount of power that can drive with ease every headphone in existence. But it is not only about more power because a dual M-Field set-up will produce upgraded sonic performance and mainly better separation and imaging, larger soundstage and greater dynamics.
The amplifier has three gain settings (low, medium and high) for better matching with various loads. You can select the desired gain from the corresponding switch at the front panel. Output impedance is also very low (0.1Ω) so it can drive low impedance loads, even sensitive earphones because it has a low noise floor. Pretty amazing if you consider how powerful it is.
The relay attenuator adjusts the volume in 1.5dB increments with a total of 64 steps so you can do fine adjustments without getting loud too fast. The M-Field can drive the Hifiman Susvara at just 40-50 steps of the medium gain setting. The only part of the M-Field that gets mildly warm, even under stress conditions, is the back side of the bottom so it will not be a problem to place it in a poorly ventilated area like a shelf.
Audio stuff
Have you ever dreamed about getting yourself a tube amplifier but you were always hesitant to do it because you were afraid to mess with tubes and their associated hassle and potential drawbacks? Well, now you can experience some of the so-called tube magic without buying a tube amplifier. How is that possible? Just get the Flux Lab M-Field, a solid state amplifier that sounds surprisingly tube-like without involving any tubes.
MOSFETs have always had this unique ability to replicate tube sound when properly implemented and in the case of the M-Field we are talking about genius engineering not imagined before at this price point. The M-Field is soulful and musical, its sound is exceptionally real and alive, the music has a natural flow that simulates the senses of the listener in a way that only the best tube amplifiers can do.
The M-Field is immersive and holographic, it produces natural and organic timbres with the most colorful harmonies that have a rich saturation reminiscent of tubes but without the usually associated negatives, like background noise, haziness, bloom or lack of control. Someone will usually have to buy an expensive tube amplifier to get rid of these negatives. The truth is that no solid-state amplifier can match a high-end tube amplifier but the M-Field can get you very close without involving any tubes or having to spend a fortune.
The M-Field is slightly warm and smooth but not dark sounding. The mid-range especially, is expressive, articulate, musical and engaging with impressive timbre quality. The sound is organic and analog-like, instruments and voices sound eerily lifelike with exceptional tonal accuracy. No op-amp artificiality, no fakeness or sterility, no metallic sheen or harsh treble. Rest assured that the M-Field is just like a musical instrument that plays music with all its realism and sentimental depth.
Technicalities
Like said, the M-Field can get you very close to high quality tube sound and at the same time is as technically proficient as the best solid-state amplifiers.
The Flux Lab M-Field ideally combines stunning musicality with supreme fidelity and transparency. Frequency response is flat and linear, the M-Field doesn't use any kind of bass boosting, treble recession or any other kind of frequency response manipulation tricks to shape the sound. The amplifier has excellent technicalities and precision close to that of the Mentor. Don't think that its warm and inviting character is going to alter the frequency response of your headphones. Bright headphones will still sound bright and warm will remain warm.
A few notes about matching
The M-Field is a good match for brighter and lean sounding headphones not because it lowers their treble amplitude like an equalizer but because it doesn't highlight their brightness and strengthens their lean nature by adding the missing weight and fortifying the bass. Some of you might think that warm and thick sounding headphones are not going to pair well with the M-Field but this is far from the truth or at least I didn't have any problem enjoying the Meze Empyrean which didn't sound that thicker or warmer because the stellar technicalities and transparency of the M-Field counterbalanced its other characteristics.
In a similar fashion, the M-Field proved equally at home with more technical D/S DACs as well as with more musical and analog sounding sources like the Laiv Harmony DAC.
More Audio stuff
The bass is full bodied and weighty, visceral and thick with exceptional layering and definition. You can easily follow the most populated bass lines and easily discern between the faintest notes, nuanced pluckings or gentle bowings on the strings, staccato or legato passages. Deep and impactful with realistic dynamic swings, the bass also perfectly captures the natural reverb of the recording hall. It is elastic but not loose, far from sounding dry or lean and at the same time is tight and as fast as the music demands. The amplifier is very dynamic and powerful but it doesn't throw the bass at the listener's face, as it perfectly harmonizes with the rest of the frequencies without drawing attention to itself or causing low-end fatigue.
The treble might be relatively smooth, mildly forgiving and devoid of any sharpness but at the same time it has plenty of energy and light, as well as extension and sparkle to avoid darkness or sluggishness while staying polite. Detail retrieval and resolution are stellar but not class leading as in the case of Mentor. The M-Field is tuned on purpose to sound less analytical and magnifying than its brother, a different kind of approach that focuses on intimacy and increased musicality rather than absolute technicalities and resolution.
The soundstage is rather unique in its presentation, not as expanded and big as in the Mentor but with amazing spaciousness despite its relatively compact size. The overall feeling is quite intimate, the listener feels like sitting closer to the performers but at the same time the depth layering is so impressive that you never experience the music as a wall of sound despite the proximity to the stage. The soundstage is extra holographic and immersive with excellent separation between individual performers and different blocks of instruments while you can always perceive the ambient information as captured in the recording.
Comparison with the Flux Lab Mentor
Some differences regarding the sonic presentation between the Flux Lab M-Field and the Mentor were described in the main course of the review but let's summarize them. Except for being slightly more powerful, the Mentor is the natural leader when it comes to transparency and overall technicalities without sacrificing much musicality. The Mentor is undeniably more dynamic and impactful, the M-Field sounds a bit softer in comparison but it has more weighty and visceral textures. The bass on the M-Field sounds fuller and more elastic with greater amounts of reverberation, it is less dry than the Mentor but the latter takes the lead when it comes to control, layering, definition and the complexity of the textures structure while it is more accurate and precise.
The Mentor is musical and engaging in its own right but it can't match the tube-like character of the M-Field which is more organic and soulful in comparison, with slightly more natural timbre and saturated harmonies. The M-Field sounds warmer, more expressive on the mid-range and smoother on the treble but the Mentor outclasses it in resolution, refinement and the quality of the textures.
The soundstage of the Mentor is larger and bigger than the M-Field, with notably better separation and class leading imaging. The M-Field is more intimate but also more holographic, however the Mentor offers a grand hall listening experience.
The Mentor has class leading neutrality, fidelity and transparency without lacking in musicality and engagement but the M-Field is undeniably one of the most musical, natural and organic sounding solid-state amplifiers ever made.
Comparison with the Aune S17 Pro
The humble Aune S17 Pro is maybe the best solid-state headphone amplifier under $1K for anyone who values musicality and timbre realism above anything else. Just like the M-Field, the Aune S17 Pro is an amplifier with a tube-like sound character while having a good level of solid-state technicalities. The M-Field is the S17 Pro on steroids, it takes from where the Aune has left and improves merely everything. From timbre realism to the quality of the textures, transparency, definition, resolution, clarity and all technicalities. If you own and love the Aune S17 Pro, then think of the Flux Lab M-Field as the natural upgrade path you have been dreaming about.
Comparison with various Violectric amplifiers
The Flux Lab M-Field is more musical and tube-like sounding than every Violectric amplifier I can think of. It's more visceral and weighty, slightly warmer and more soulful with an overall technical performance somewhere between the V222 and the V330 but can't reach the V550 which is only comparable with the Mentor.
Comparison with the Cen.Grand 9i-906
A rather unfair comparison as the Cen.Grand 9i-906 retails for $4190 so it will not sound too odd if you read that this amplifier successfully combines the best characteristics of the M-Field and the Mentor. However, it doesn't have the personality of the M-Field, not of the Mentor, which both have their own unique sound character that many people will prefer over the Cen.Grand 9i-906. Additionally let's not forget that the Cen.Grand is out of reach for most people out there when both the M-Field and the Mentor are affordable and some of the best bargains in the audio industry.
Conclusion
The Flux Lab M-Field and the Mentor are like variations on the same musical theme and people familiar with music synthesis will definitely know how difficult it is to write inspired variations of the same theme.
I could end this review by just copying the conclusion of the Mentor review and replacing the word “Mentor” with “M-Field”. It would read like this:
“With the introduction of the Flux Lab M-Field, high-end quality has become more affordable than ever before. Undoubtedly, the Flux Lab M-Field reigns as the most cost-effective high-end headphone amplifier available, featuring outstanding value for money and securing its position as one of the top bargains in the audio industry.”
Flux Lab Acoustics has cleverly made two high-end headphone amplifiers with slightly different sound signatures in order to cater for the two larger audiophile groups. The ones who desire the best possible technical performance but are not willing to sacrifice much musicality and the others who most value unparalleled musicality but are not willing to skip on technicalities. Whether you belong to the first or the second group, Flux Lab Acoustics have you covered and without the need to spend a fortune. Be it the M-Field or the Mentor, rest assured that you are buying an exceptional high-end headphone amplifier at an unbeatable price.
The review sample was kindly provided free of charge in exchange for an honest review.
The price of a single M-Field is $1299 and you can buy it from Flux Lab online shop. You can take advantage of the pre-sale offer price which is $1199. The amplifier ships from the EU so buyers within the EU zone will not have to pay import fees and tax. The M-Field is currently in production and will be available for sale very soon.
