i bought an acmee from linsoul(amazon) wouldnt read any cards.emailed linsoul explained problem they suggested a few things.tried them all,told linsoul. asked for a refund they replied would i like a discount. why would i keep a player that didnt work.had to insist on a refund. i really like the look of this player,was disappointed.have two sansa clips which ive had for years,no problem

Am I the only one who hasn't had problems with this DAP's SD card? I have used several and now I am with a 128GB SD from Sandisk, formatted in FAT32. Sorry, friends, if it were up to me I'd help you out.

So the questions come down to:
1) Has anyone ever successfully used a 256gb card (the manufacturer's claimed limit)?
2) If so, FAT or exFAT?
3) What were the other specs on the card?

Player is now reading the 256GB card perfectly... after I deleted the two folders named in Japanese.

I just got one of these. The feel is awesome, and the sound is wonderful through my HD6XX headphones. It's got USB-C, so it seems they made a hardware modification at some point. That's the good news. The bad news is there's a small rattle inside, which kind of diminishes the impression of solidity given off by the metal construction. The even worse news is that the player fails to charge! Maybe they haven't nailed that USB-C transition. Before the battery died, I tried using the USB DAC functionality. I put that setting on Yes, but it didn't appear as a sound output device on my Mac. Maybe again that USB-C port is having trouble. There's a Settings choice called USB Charge Yes/No. Not sure what that means. It arrived set to No, but I changed it to Yes right after I changed the menu language to English. But either way, Yes or No, it had no effect on the USB-C port's ability to actually charge the battery. It's on firmware version "G".

I forgot to mention - I used a 128 GB Samsung EVO Select card, formatted ExFAT on my Mac. There was some glitchiness. The player reported "No TF Card" when I chose the "Scaning Music" menu item (hope they fix that typo). But if I rebooted the device with the card in, and it must have done the scan during the boot up because then my music appeared. I can easily live with the single level of folders thing, but in each folder the FLAC files seem to be in random order. That's by far the biggest software flaw, IMO. They should be sorted by filename.

Bad luck with the battery problem, but it should be covered by the battery.
The bad order of the songs, is something logical in this type of DAPS. A sorting of the FAT table is required, which you can do with an external and free software like this one:
https://www.softpedia.com/get/System/File-Management/FAT-Sorter.shtml

Firmware v2.1.5H
http://www.acmee.cn/index.php?s=index/show/index&id=596

Thanks for the tip re. FAT table sorting. I got a replacement from Linsoul, no problem, and with that utility I'm now good to go! I put a 3.5mm plastic dust cover/plug into the LO port - I'm a little paranoid that I'll accidentally put my headphones into the wrong one, since they're right next to each other. I also wrote to Acmee and pointed out a typo in the menu. They said they'll fix it in the next firmware release.

Sounds great.
I'm glad.

what about it out put power ? i didn't see in spec sheet

so, it just around 320 mw @ 32Ohm load right?

Easily, even more so.
But you must take into account the output impedance, hence the voltage is not constant, measuring with different impedances.

thx for ur answer dude , it may come to me next week hope it can be sound great with my ISN H40

Just a side note ... the MF-01 does not come with a case of any kind, and its shape is somewhat unique. I happened to have a Hiby hard earphones case on hand, and discovered the MF01 fits inside it *perfectly*.
https://store.hiby.com/products/premium-leather-storage-case
It's on sale, but still costs half what the player does - so not necessarily a no-brainer. Seems pretty well made, though.

Can you talk about the line-out, please?

Believe it or not, I've never really used it, so I can tell you little or nothing about it. I'm sorry.

@eyan What is it you're interested in about the line out? I've got a Schiit Fulla I could run the Acmee LO into - but I don't have any way to take measurements or do anything quantitative.

The line output is designed to be connected to an amplifier, it has different electrical characteristics than the headphone output (different output impedance, among other things...). It usually has a fixed voltage (line output) or variable voltage (Pre-Out). But normally, it should sound the same, both one and the other, although there are times when they have different SNR or THD specifications, because the circuitry after the amplification may not be the same. The interesting thing about a line output is its voltage, SNR and THD, which will allow you to decide between one source and another, as well as the pure sound quality of each device.