@bjd1, thank you very much for your support.
A discussion, without wanting to stir up controversy, should be positive. Apart from writing reviews, I also try to answer questions. It's still a matter of respect for the readers.
On the other hand, I feel privileged as a reviewer, because it's not an obligation, it's doing something I like, in the best way I can. I learn from all the comments and some of them indicate that I need to improve... I'll take it as another challenge. For now, I'll keep writing and taking note of those comments to keep growing.
Regards.

@NymPHONOmaniac, I follow up on your answer.
From my trained electronic point of view, I look for a kind of rigour in DAPS: I look for a flat response and a low output impedance. Perhaps these are the most important elements for me, apart from the sound. A high impedance changes the frequency response of some connected headphones, as does a non-flat response. What I like least is a frequency response of a DAP that has a considerable loss in the low end. In the trebles I am more permissive. The MF02s has a 1.5dB roll-off at 20kHz, I don't like that either. But the Ziku has a drop of 6dB at 20Hz, that's a lot for a bass lover like me.

And that's something that happens with other DAPS, like the F.Audio, of which I only still use the S1 and I don't use the XS03 or the FA3.

Thanks for the review mate.
have you tried the ACMEE Magic Sound 4?

Yes, I received it a few days ago and I must say that it is a clear heir to the MF02S. So much so, that its frequency response is the same, as well as its output impedance. The sound has the same colour and I can affirm that it is a dongle version of the MF02S. I think that ACMEE has been inspired by many things from their DAP, to offer a sound in that line, saving the distances, of course.

@cqtek thanks for the review, and your voice to MF02S limitation. The latest firmware update solve some of them, such as slow SD card scanning.

thats good to know...since you praised the mf02s for its sound. I don't know how true it is but 500mw @32ohm for a dongle is crazy. Looking forward for your review of the dongle. Thanks for your impressions mate.

I think the power specifications are too optimistic. If the MF02s doesn't reach that value, giving, according to my RMS measurements, 190mW at 32 Ohms through the BAL output, I don't think the dongle will reach that power delivery either. The problem is never voltage, it is likely that the dongle will reach 4V on the balanced output, as other dongles do. The issue is with the current delivery, which in conventional operational circuits, hardly exceeds 90mA.
In any case, we will find out when I make the measurements.

I agree, I have the same doubts since dongles are made keeping mobile phones and their battery life in mind and mobiles usually top out at 100ma, especially iPhones. I think L&P w2 is the only one to pull around 120ma . Even the mf02 with battery does only well at high impedances (100ohms and above) to reach the power level through higher voltages as per your measurements.
xDuoo recently announced their Link2 Bal which apparently puts out 250ma, which is again skeptical.
Anyway I will wait for your assessment of the sound 4.

Last week I also received the xDuoo Link2 BAL, so once I have taken the measurements I will know for sure. But I have a lot of work ahead of me with other reviews.
As for power, the Hidizs S9 Pro, according to my measurements, can deliver 230mW at 32 Ohms per BAL. My review of that dongle is also here or on my blog.
Another Hidizs, the DH80s, delivers 220mW at 32 Ohms per BAL. From my experience, Hidizs usually delivers what it specifies. Tempotec is also very reliable, but the E44 delivered less power than specified. The Earmen Sparrow delivers what it specifies, but is below the S9 Pro.

We'll see how the ACMEE Magic Sound 4 AK4493EQ and the xDuoo Link2 Bal perform, although I think their measurements will be below specification. In reality, though, the most important thing is the sound. In a quick comparison between the two, the SE output of the Magic Sound 4 AK4493EQ sounds very good, while the performance of the Link2's balanced output is better than the same output of the ACMEE. Don't take this as a reference, it was just a quick test.

Yes, Hidizs measures true to specs among all your reviewed dongle dacs. It is good that E44 provides some competition for the S9 Pro, in fact it betters the S9 Pro according to your review. I believe Its the first with a dual dac in its segment and seems like it paid off well. I am not sure regarding its power though, because OspreyAndy states that his unit is the most powerful dac he tested, besides the DACport HD. May its just your particular unit, or may be it's sound characteristics cause it to be perceived as powerful — I don't know. Anyway you both agree on its SQ.

Thanks for the quick impressions mate. Looking forward to your full review on both of them. I am more excited for the Link2 since its a dual dac, I guess it could have an upper hand in terms of soundstage and seperation. Not sure though, just my theory. Lets see.

That's right, in terms of sound, the E44 is one of my favourites. Tempotec has managed to get the best out of this dual DAC on this occasion. They tried it twice, with the E35 and also with the BHD. The E35 is quite good and the BHD is inferior.
I see you have read a lot about the E44 and what Andy says about it. I even commented in his review that it wasn't that powerful by my measurements and he commented that his tests with hard to move IEMS say otherwise. It's not all numbers and there is also empirical testing with real loads, like our headphones.
In that sense, I connected my TinHifi P2s to the balanced output of the Magic Sound 4 AK4493EQ and also the xDuoo Link2 Bal and I could see that the xDuoo is more powerful, because it was able to move the demanding P2s better. I did not test with the E44.
By the way, the Link2 Bal uses the same dual DAC as the E44.

Yes, if you do have the E44, I'd love to see it compared to the Link2 in your review — Dual Dac Battle .
I did read a lot, infact your review and comparison with s9 pro got me interested in them and especially considering they cost less than the s9 pro.
Considering P2s low sensitivity of 90db, glad to see it performing better with Link2. Low sensitivity does require higher current so can't wait to see your measurements. I have read almost all your reviews on dongles. Your measurements are incredibly helpful. If possible, please do test out the P2 with E44 aswell. Just trying to understand whats going on with E44.....just read your comments on Andy's site.

Coming to dual dac dongles, Shanling announced UA5. Daul DAC and dual independent amps. Seems pretty interesting!!

Hmm...
I'm sure properly modded Z4 will beat this... ridiculous something

do you compare it with z4 balance output? people said its SE is terrible and use only balance output

I sent my Z4 to a good friend of mine, to make some improvements on it. There have been some problems during shipping and it is still travelling. I don't know when I will get it back. But my intention is to make a comparison between the two, once I get it back in my hands.

I read your recent review of the V6. While I'm not interested in Android and all that, how would you say the MF02s compares to one of those Fiio/Cayin/Shanling-style-ect-ect mid-range touchscreen DAP's... sound-wise?

I can only compare the MF02S with the V6, because I do not own another mid-range DAP. It is a difficult choice in sound. But there are two or three details that make me go for the V6. First, output impedance close to zero: This is something I appreciate above many things, because the DAP will not alter the sound of the connected headphones. Another thing is if you like to experiment with those changes, you can choose the MF02S.
Second, the battery life is superior on the V6. Third, there are little things, like the V6 has a touchscreen, you can use Tidal, it's a newer product susceptible to improvements, it comes with a case, it doesn't heat up as much, the use of Android ensures a superior handling experience...
In terms of sound, both are very good for their price. I think there's a bit more scene and depth in the V6, while the MF02S is a bit more neutral.
The MF02S is more powerful per SE for impedances above 33 Ohms and the same goes for BAL.