Total Bet On Pure Sound
- Above all, the enormous sound quality.
- Powerful, high output voltage.
- Very good construction and level of finish.
- Volume control and button operation.
- Large display.
- Simple operation.
- Constant development.
- Battery life.
- High output impedance.
- Can get quite warm.
- Although the screen is large, it is underutilised, the playback screen does not display the cover art and the lettering in this mode is small.
- When switched on, the system can take a long time to start up, because it is scanning the memory card. At this time, there is no warning of what is happening.
- There is no instruction manual in English.
Link to the Store
ACMEE Audio is once again releasing a new DAP, in the line of the so-called «obscure» players from China. The MF02s is the successor and big brother of the great MF01 and shares some similarities with it in its external design, although the differences are more than obvious. Starting from the beginning, this model was intended to be called MF02 and was initially designed with an AKM DAC, if I remember correctly, it was the AK4497. I guess the fire at the AKM factory changed the plans of this brand, as well as many others, in favour of choosing Sabre chips. My guess is that the tables will soon turn and AKM chips will flood back into the market. I think Sabre would do well to bear in mind that this is entirely possible and I hope they are also designing new models. Although I have strayed off topic, I wanted to stress that the ES9038Q2M chosen is nothing new. And, although only one has been chosen, ACMEE wanted to enhance the other components of the circuit, which invest in a Dual-DAC model. For example, the motherboard uses a 5V power supply, 2 LT3529 low noise power chips, 3 TI TPS735 ultra-low noise LDO power supplies and the audio board uses 2 TPS375 to provide digital and analogue power to the ES9038Q2M. 2 LT3042 provide audio power. The power supply to the operational amplifiers is fed from ±7V, which is boosted by the LT3471 to ±8V and then regulated to ±7V by 2 very low noise LDO power supply chips respectively, which achieves low power supply noise while providing fast response. At the headphone amplification level, the normal version of the MF02S uses 2 OPA1612 + 2 HDAM9988 + 2 OPA1622, of which the OPA1612 takes care of the IV conversion. I say normal, because there is a «special» version that uses 2 HDAM2627. The version reviewed here will be the «normal» one and I already say that the sound is good enough not to miss the special version. Or, perhaps, yes.
- Colour: clear grey.
- Body material: 6060 aluminium.
- Display: 3-inch 480×854 IPS non-touch screen.
- Audio formats: WAV, FLAC, APE, MP3, AAC, M4A, ALAC, DFF, DSF (with firmware update, continuous update)
- Input: USB Type-C
- Bluetooth: 5.0/APTX-HD
- Output: 3.5mm PO/LO, 4.4mm balanced.
- Output level: 3.5mm single-ended: 3.5Vrms. 4.4mm balanced: 7Vrms.
- Output power: 3.5mm single-ended: 142mW(32Ω). 4.4mm balanced: 284mW(32Ω).
- SNR: 3.5mm single-ended : 112dB. 4.4mm balanced: 118dB.
- Frequency response: 15Hz-45kHz.
- DAC: ES9038Q2M.
- MCU: STM32H743IIT6.
- Main frequency: 480Hz.
- IV Op Amp: OPA1612x2.
- Main Op Amp: HDAM9988x2.
- Amplifier: OPA1612x2.
- Audio power supply: ±8V + ultra-low noise LDO at ±7V.
- DAC power supply: ultra-low noise LDOx4.
- Size: 115mmx52mmx21mm.
- Weight: 178g.
- USB DAC: supported.
- Firmware upgrade: supported.
- Battery capacity: 3000mAh.
- Playback time: 6.5 hours.
- Charging time: 2 hours.
- Built-in memory: 32GB.
- Expandable memory: supports up to 256GB
The MF02s comes in a small dark box with dimensions 147x89x51mm. On the top of the main side is the brand logo and below it the name of the model, in silver ink. At the bottom is the brand’s web address, written in the same way. Near the left edge, a clear blue stripe is visible through a slit. This means that the box is pulled out sideways, stretching to the right. On the back side there is little else, some logos of the certifications they comply with, as well as other descriptions written in Chinese in silver letters, on the base of the box. After sliding the lid sideways, you can see the DAP inside a whitish pouch, inside a thick black foam mould. After removing it, with some difficulty, you can access the rest of the accessories, some of them inside white cardboard boxes. This is the complete contents:
- The ACMEE MF02s.
- One screen protector.
- One USB to USB Type-C long charging cable.
- One USB Type-C male to USB Type-C male short cable.
- Instruction manual in Chinese.
- Warranty certificate card.
There is no case, although a screen protector is appreciated. As is typical of obscure DAPS, the instructions are only in Chinese, which is a terrible thing if you want to sell in the rest of the world. In conclusion, the presentation is sober, with the minimum number of accessories and little respect for the rest of the world that does not understand Chinese.
Construction and Design
The DAP is a very solid 6060 aluminium tablet, with a 3 inch IPS non-touch screen, with a resolution of 480×854. The screen is large, but the lettering is small. So far no cover art is displayed, using firmware v1.1.2.B, although at least the complete name of the songs can be displayed. The size is 115mmx52mmx21mm, with a weight of 178g. It really feels dense, even though the size is not very large. On the top left edge there are some slots, reminiscent of the MF-01. Between them is the power button. On the right side is the large potentiometer, which is also a button. It moves in steps, showing a very nice, yet precise opposition to adjust the volume with maximum definition. On the right edge, from top to bottom, is the back button, the (larger) play button and the forward button. All buttons are round. Finally, on this side, there is the slot to insert the microSD memory, which is compatible up to 256GB. On the bottom edge, from left to right, is the balanced 4.4mm output (gold-plated), the 3.5mm SE output, which in turn is the line output. Finally, there is the USB Type-C port. On the right edge there are only two buttons, the mode button at the top and the back button at the bottom. On the back there is only the brand logo, the name of the model, at the top and at the bottom the logos of the certifications it complies with, as well as the web address. Everything is written in a very subtle white ink, which makes it difficult to read.
The external design is simple, with a few signature touches, keeping a parallel line with the previous DAP. Despite this simplicity, the MF02s stands out for its presence, its slots, its edges, the large volume wheel, its buttons and the large screen. However, the screen is very unused and the letters are very small, with no possibility to make them bigger.
Internally the MF02s uses the Sabre ES9038Q2M DAC, 4 OPA1612 for the different amplifier stages and two HDAM9988 for the main amplifier circuit.
The battery is 3000mAh.
ACMEE’s philosophy has been to use the best components around a single DAC, to get the best out of it. It is clear that the emphasis is on delivering the best sound, with other issues taking a back seat. The construction is very good, although the back cover does not appear to be easily removable, with no screws visible and appears to be glued on. One of the issues, on a secondary level, is the utilisation of the screen. In my opinion, it is still insufficient, basically because of the size of the letters and the small amount of information displayed on the playback screen. For now, not much more than the MF-01’s display, which is the basics.
One last, insignificant detail, but the 4.4mm output is silkscreened as «4.4BLA».
The MF02s has a balanced 4.4mm gold-plated connection. A shared 3.5mm output, for single ended headphones and for line, selectable from the interface. It also has a USB Type-C port for charging, use as a DAC, external memory card communication and internal memory. All of these are also selectable from the interface. It can be used as a Bluetooth source, version 5.0 and supports APTX-HD. It can also be used as a Bluetooth receiver.
The level of connectivity is not bad, it is surprising that everything can be activated from the interface and that some modes are not immediate. Use as a DAC or as a USB disk may require a reboot of the DAP itself.
This is where the MF02s acts as a true obscure DAP. Although the operation is very simple and intuitive, there are only two screens dedicated to the options, there is no explanation in English, and no manual can be downloaded from the website. There is a manual for updating the Bluetooth, which is not at all easy. It is, of course, in Chinese. I’m not going to spend the whole review explaining how the DAP works, when the brand itself doesn’t care about it.
The first contact with the DAP is not the most pleasant. I inserted my 128GB micro-SD memory card and it took a long time to switch on. The reason for this is that the MF02s scans the card the first time. This can be a long process, depending on the number of songs. There is a limit though: 4500 songs. I think the MF-01 does not have this limit. At least it safely recognises two levels of folders and navigation between them is easy and fast. Once the entire card has been read, the next power-up is faster, although it is relatively slow compared to other DAPS. If you want to add more songs, you can connect it as a USB disk or you can add it to the SD, in the traditional way. The DAP creates a folder in the root of the SD, called «MF02S_OBJ_INFO», where it stores the contents of the folders. To update the list of folders and songs, the memory card can be scanned manually, via an option. Actually, I don’t recommend this DAP if you are a person who constantly updates the memory card, because the scanning and start-up times are slow and sometimes not entirely safe. Sometimes it has been necessary to delete the folder «MF02S_OBJ_INFO», so that the DAP reads the card again, correctly, all the songs. I hope this process will improve and become more robust. Fortunately, firmware updates are common, but I don’t know how far they will go. In my opinion the MF-01 model was unfinished, with inefficient reading of two levels of folders. In its defence, ACMEE says that it puts all its efforts into producing the best sound and using the best components. But all that is of little use if their product is unwieldy to the point of being unusable. I don’t think the MF02s is like that, but I do think it is very «special» and, at times, a little bit desperate. Fortunately, the sound is worth it, as they say. We’ll have to be patient with those firmware updates.
Another thing that happens when the MF02s is new is that the battery needs to be calibrated. This process is simple, just let the battery run down by using the DAP and perform a complete charge cycle. After this process, the indicator asking you to calibrate the battery will disappear.
As mentioned before, the connectivity options may require a restart of the DAP itself to be effective, which is to be expected.
Believe it or not, the Bluetooth menu surprised me, because it is very explicit and contains a lot of information. Pairing is quick and devices can be chosen from a list. Bluetooth is bi-directional and to the point of using it, I was surprised that it was also a receiver, which is unusual and a big plus.
Access to the different screens is via the «M» button, first disk explorer (internal and external), then options screen, where the last option is an extra screen of system options. The last screen is the favourites screen. As with the MF01, pressing the volume wheel adds or removes the «favourite» property to the current song.
The screen is very large and when in play mode, the letters are small. Otherwise, they are somewhat larger. With firmware 1.1.2.B, the texts are now displayed complete, because they slide across the screen, although the cover art is not displayed. According to my information, they will be shown in future firmware updates.
In the end, the handling is simple. The use of volume and buttons is very effective and pleasant. It is not gapless, but the skip/pause between songs is very small. But I am sure this can be improved with future firmware updates.
Battery life is as short as specified, just over 6 hours. Even more so, if you turn it off and on a lot, perform card scans or consult the song list a lot. To maximise battery usage, little interaction with the DAP is recommended.
There is a special firmware for .wav files, which tries to increase the sound quality. I don’t use this format regularly, so I haven’t tested it, the current sound quality is sufficient for me.
The DAP gets hot, it doesn’t burn, but the temperature is high for a portable device, both on the screen side and on the back side. It is clear that generating the best sound requires an expenditure of energy and the heat is a clear symptom of this.
All in all, there is no doubt that ACMEE has created a DAP with sound quality clearly in mind, leaving other issues in the background. Personally, I think that better handling, less heat and longer battery life would be great allies in increasing the virtual value of this good DAP.
Starting with the output impedance, my results are as follows:
- Zout SE = 10Ω
- Zout BAL = 22Ω
For my taste, I have always been clear in this regard, they are too high. I am an advocate of a low output impedance, around 1Ω. I must say that ACMEE is aware of these values and they will have their reasons. The real result, though, is that the frequency response in headphones with BA drivers will suffer from alterations. The curious thing is that these are not always bad, in the case of one of my favourite IEMS (Rose QT9 MK2), it is for the better. This is not to say that the sound produced is bad, it is simply different from other sources and normally, the tendency is to smooth out the mid-highs and highs of these headphones, although, sometimes, the bass is also boosted, slightly. Dynamic drivers are not usually harmed in this respect, this effect is more prevalent in IEMS with BA, low or medium impedance drivers.
No Load SE
ACMEE indicates that the SE output goes up to 3.5V, in reality it goes higher (3.75V), but the Zout has to be taken into account.
The maximum output without visible distortion is 1.2V. This implies a power of 96mW.
Maximum output without visible distortion is 2.35V. Power is 170mW, well above the claimed 142mW.
Maximum output without visible distortion is 3.3V. Power is 110mW.
No Load BAL
ACMEE indicates that the BAL output goes up to 7V, here it also goes higher, 7.34V.
The output power is similar to that of SE, approximately 90mW, which is about 80mA. This seems to be the maximum current the ACMEE can provide.
Maximum output without visible distortion is 2.5V. The power is 190mW. As the current limit is around 80mA, it is not possible to provide 284mW at 32Ω. This figure would imply a current of 94mA and a voltage of 3V. In reality, it is not far from these values, making it clear that the MF02s is very powerful. If the Zout were lower, it is possible that it could be even more powerful.
The maximum output without visible distortion is almost 6V, which is a very high value indeed. In this respect, the MF02s is a savage, but it also heats up on par. We are talking about 360mW, a very high figure.
The MF02s is a warm sounding DAP, there is a slight roll-off, approximately 1.5dB at 20khz. There is no roll-off in the low end, reaching linearly down to 10Hz. The frequency response extends beyond 40kHz.
And finally we come to the sound section. So far the MF02s have survived my comments with better or worse marks. But in this section I have no doubt, it is a machine for making music. And in a very natural way. I recently tried the Hiby R5 Saber and I was not convinced, because of a somewhat unrealistic recreation of the high end, as if it was forced to provide a greater sense of three-dimensionality. None of this happens in the MF02s. The sound is eminently big in its own right, with a very powerful and energetic low end, which does not obstruct the upper ranges. It is true that this is a warm profile, with a smooth representation of the mids and treble. And this is real, it’s not just an assessment, there is a subtle and progressive drop from 10kHz onwards. But this effect is not very important, as the Zout can have more impact on the final sound. Again, I am against this particularity, but sometimes I get tired of fighting against the elements and proclaiming to the four winds the advantages of a low Zout. And this occasion was one of them. So I plugged in my favourite headphones and chose to enjoy. The result is a sound that possesses a high musicality and also spatiality. It is soft, but defined, very pleasant, you can turn up the volume without anything sounding shrill, forced or unreal. Everything occupies a good place and nothing is dismantled in the process. There are times when the music comes on top when the volume is turned up. Here it doesn’t. On the contrary, a greater energy expands the sound and the scene becomes even fuller. The sense of three-dimensionality is excellent and the sound spreads out in all directions with astonishing ease, even giving an intimidating, enveloping feeling. The pressure that the MF02s’ energy brings to the sound seems to be felt, adding an almost oppressive physical sensation due to the grandeur of its sound. This kind of sensation is only elicited by very select sources. Although the sound has great expansive capacity, this sense of energy is greater. This characteristic of size and power is felt at the first contact, generating a very high feeling of attraction and sound immersion, from which it is difficult to get out and which is not found in other inferior sources.
Making a distinction between the SE and BAL output, the sound from both is very good, but that feeling of power and greater amplitude is perceived more easily and in a more pronounced way from the balanced output. That’s why, practically, all the headphones used have been through this connection; when you try it there is no turning back. Even so, the ISN H40s connected via SE are capable of delivering even more than I expected of them, as an example of the great quality that this output treasures.
In general, the stage is vast, the low end acquires a special dimension, whose depth becomes abyssal, generating a bass with a soft and smooth texture, which can be tasted throughout its journey, recognising all its phases, the initial strike and how it decays over time, while its surface is distinguished as rough, until it disappears. This very descriptive level of the lower zone, this quantity of planes, this level of separation, of depth, of definition, generates an enormous lower zone, very rich, of great resolution, very open and uncongested. And yet, full of power and that warm feeling that doesn’t hide or camouflage anything. Definitely, the MF02s is a great DAP for bass lovers.
The mid-range is equally enjoyable, very rich and detailed. Thanks to the great sense of openness and separation, nuances are very easy to appreciate, but without losing the smoothness and excellent musicality. The sound in the mid-range is sweet, melodious, full-bodied and soulful, very airy and clean. The sense of power is not lost, but the delicacy with which the energy is displayed is noteworthy and praiseworthy. There is plenty of punch, but no stridency whatsoever. I don’t find the MF02s offer any favours towards instrumentation or vocals. Throughout the midrange, the level of realism is extreme, very natural. The expressiveness of nuance and micro detail is overwhelming, the level of resolution makes it easy to expose small elements and they are presented with the space they require, without overlapping or hiding behind anything. Each note has its space, its place and there is a suitable position for all of them. There is no congestion and the space, the separation, generates a level of transparency and clarity, which further enhances the stage, by way of mutual feedback.
The sound is not analytical, as the representation falls on the soft and sweet side, with a timbre that has a warm and natural tendency. This does not detract from the very high level of resolution and detail, as I have already mentioned.
Moving on to consider the upper range, it persists in the idea of smoothness, definition and a high level of resolution. The treble is described with dexterity, skill, speed and eloquence. They have the capacity to be explicit in those headphones with enhancement in this zone, without hiding their capabilities, exposing them with total naturalness and without falling into a clinical or unrealistic representation. The upper zone has a very slight attenuation, without it being clearly perceptible, beyond a warm tendency of the DAP profile. By this I mean that the absence of air is not perceived, but quite the opposite.
Concluding, as usual, with the considerations of staging, separation, instrumental recreation and positioning, I have provided ample detail on the level of these technical characteristics throughout this description. Above all, I have mentioned, in no uncertain terms, that the scenery is outstanding, as is the separation. The recreated scenery is larger than a hemisphere, although this sensation can be improved depending on the headphones used, increasing the perceived three-dimensionality, as I mentioned at the beginning. I don’t think of the image as ethereal or volatile. Although the amount of air and the distance is very great, there is a good level of energy that allows the elements to be brought closer to the listener, placed in the centre, adding an extra body, but without any congestion. It is as if the elements enjoy a more physical representation, occupying a real space in the scene. In that sense, the level of authenticity and naturalness reaches a higher level, generating a representation that distances it from any impostured or artificial sensation, adding a presential ability difficult to notice in other DAPS I have tried. Needless to say, with such good separation and distance between elements, the background is as dark as the connected headphones can get.
All in all, ACMEE has used all its know-how to deliver the best sound for the price of the MF02s. It is clear that there are no compromises for the sake of appearances and that all the energy used is fully transferred to the music, with all that this entails, in terms of power, technical features and musicality, without losing sight of the smoothness and sweetness of an undoubtedly exceptional sound.
The Zishan Z4 is another paradigm of obscure DAP. Zishan tries to make high-end circuits available to everyone. This time it uses a Dual DAC ES9038Q2M. But he uses very common electronic components, to complete the rest of the circuit. Thus, the end result is a product that may sound very good, but whose sound is penalised by the inferior quality of these electronic components. This is why many hobbyists modify this type of DAPS, in order to improve the sound.
It is very similar in size to the MF02s and also has its firmware imperfections, but the price/performance ratio is superior, because it is worth a third of the price. It is very powerful and the handling is a bit better, although I must comment that it sometimes crashes. It is faster, does not require card scanning, the display shows more information, including the cover and the battery life is longer. It even weighs less and doesn’t get as hot. Now, does it sound as good as the ACMEE? I’ll discuss it below.
In the low end of the MF02s I find more depth, air, texture and descriptiveness. In the Z4 the punch seems more concise, but simpler. The MF02s’ bass fills the soundstage more, and the scene is enlarged with it, appearing wide, broad and spacious; whereas in the Z4, the soundstage expansion seems more limited. The MF02s’ greater bass depth provides a more sensory perception of the sub-bass, feeling more physical and corporeal. Even the timbre and execution is more realistic, natural, especially in very complex and complicated bass lines, which is where the MF02s brings out its greater skill and resolution in representing bass more delicately, faithfully and accurately. In these situations, the Z4 takes the middle road, demonstrating power, but not the control or fidelity that the ACMEE brings.
The differences in the mids of the two DAPS follow the same script as explained in the lower area. The simplicity of execution is maintained in the Z4, while the MF02s offers a clearly palpable superior richness. The wide scene, transparency, level of complexity, expansiveness, definition, resolving power, precision, naturalness, timbre, depth, descriptive talent and, ultimately, greatness of sound, is lost when switching to the Z4. The elasticity, the range, the texture, the amount of nuance that comes through in the voices of the MF02s become mundane and imperceptible in the Z4. The same is true of the instruments, the richness that exists in their development is overlooked in the Zishan. The MF02s conveys soul, passion and warmth, the Z4 is more earthy, cold and sober.
In the upper range, the profile of each comes to the fore: the Z4 is cooler and more analytical, the MF02s is warmer, softer and more controlled. While the Z4 is more expressive, incisive and penetrating in this zone, the MF02s shows its delicacy and a more subtle, quiet, gentle and less rebellious timbre than the Z4. But that doesn’t detract from the ACMEE’s lack of resolution by any means. Its descriptive level and sheer resolution highlight the greater energy provided by Zishan in this band, without it being able to unravel all the music that the MF02s does generate in the upper range.
As one of the clearest differences, as I have discussed in each range, the scene level is different in both DAPS. The MF02s, from the low range, already offers a higher level of depth and width. In the mid-range, the distance between elements is perceived as superior and the body of both voices and instruments expands the scene and develops it in a more three-dimensional and voluminous way. The upper zone adds the necessary air to extend it to that higher point and the result is clearly perceived. The descriptive level and the higher resolution add an ornamental richness, incorporating more complex elements to the details, such as a more palpable texture, a more recognisable path in the execution of the musical notes, more elaborate and complex nuances, which give the sound produced by the ACMEE that soul that I mentioned before. Really, despite the fact that the price is three times higher, it is at another level. Which, on the other hand, should be quite normal.
As a defence of the Z4, it is quite likely that in the future there will be a second round… Let’s see if it is possible to repeat the battle, but with a Z4 in other conditions…
ACMEE has created the obscure DAP paradigm: pure and imperfect. Pure in sound, imperfect in some issues such as handling, battery life and a firmware that is not too polished, but has room for improvement. Aesthetically, there is no doubt that the MF02s is attractive. It is a good rectangular piece of aluminium, with a large and somewhat wasted screen. Perhaps it would have been better to use a smaller screen, given the amount of information displayed on it, if this would have increased autonomy. The aesthetics follow in the footsteps of its predecessor, with a large volume wheel/button, in addition to those flaps and slots. It is accompanied by 6 buttons that work perfectly, quickly and efficiently. On the flawed side is the short battery life and slow card scanning, among other aspects already reviewed. But on the pure side is the sound. And here there is no room for doubt: ACMEE has gone all out to deliver the best sound with the MF02s. If other issues have to be sacrificed for this, it doesn’t matter. It doesn’t matter that the battery drains after a few hours, it doesn’t matter that the Zout is relatively high, it doesn’t matter that it gets warm, it doesn’t matter that the firmware is slow and unfinished. It matters the purity of the sound, it matters the scene, it matters the (very big) power, it matters the amount of energy transferred to the music, it matters the definition, the resolution, the details and the micro nuances, it matters the naturalness, the realistic timbre and a sound with body, soul and feeling, sweet, smooth and controlled. If you care about all this, the MF02s is for you. Everything else is relative.
Earphones Used During Analysis
- Dunu Falcon Pro
- NiceHCK Topguy
- NiceHCK Lofty
- NiceHCK EBX21
- Smabat M0+Super Point Driver
- LZ A2 PRO
- Ikko OH1s
- Ikko OH10
- Reecho SG-01
- Rose QT9 MK2
- ISN H40
- NS Audio NS5 MKII Extra Bass
- Takstar Pro 80
- SoundMagic HP150