S1 MP3 player
S1 MP3 player tech specs
- Company: Various
- CPU: Actions ATJ2085[1] (Z80 clone)
An S1 MP3 player is a vague term for several MP3 players made in China, based on the Actions ATJ2085 microcontroller.[1]
They can usually do a few other things too (such as playing an included FM radio, and even recording from it or from an external microphone to a custom format), but playing MP3 files is the main one. If you're looking for something complex and featureful, an S1MP3 player isn't it.
As noted back in 2005, the specs then were pretty limited.
The internal NAND flash memory was typically between about 256 MB and 2 GB.[2] The filesystem should be formatted as FAT or FAT 16, not FAT 32 or anything else.[3] Files are listed and played in the order of when they were copied to it, not alphabetical order.[3]
It supports up to 130 directories, each of which can contain up to 99 files.[1] Subdirectories are not supported.[3] These aren't especially restrictive limitations, given the typical volume sizes.
It supports 8 — 448 kbps, 8 — 48 kHz, CBR and VBR MP3 files, and displays ID3 tags.[3]
In the twenty-first century
S1 MP3 player circa 2025
The PCB inside
Jerry Chip AK24BP2D054-51C8
NS8220 2431Y1
I bought one in 2025, and it seems slightly more advanced. The firmware identifies itself as version "1.20 2020/12/09". Instead of having its own internal memory formatted as FAT 16, it takes a microSD card formatted as FAT 32.
The shop I bought it from claims it can use a maximum volume size of 32 GB, but only play 128 kbps MP3 files in the root directory. Experimentation quickly proved all of this incorrect.
32 GB was too much. I didn't try 16, but 8 was fine. I managed to copy more than 750 songs to it before running out of space, and it could queue up the whole lot. As with the older players, the files are still played in the order they're copied onto the microSD card (at least mostly, at any rate), not alphabetical order. Files with long names will load, but those names will be displayed in truncated FILENA~1.MP3 style.
As with its older siblings, it can play all manner of MP3 files. It could cope with anything from LAME that I threw at it, from 8 kbps to 320 kbps, including both constant and variable bitrates. Curiously, the display insisted every file was 128 kbps, even when it clearly wasn't. It can't play AAC, FLAC, Ogg Vorbis, or wave files, which is to be expected. I couldn't get ID3 tags working at all, whether V1, V2, or both combined.
I'm not sure what the exact filesize or track length limit is. It could cope just fine with a 320 kbps, 48 kHz copy of my hour long "Alien Ocean (Day)", which clocks in at well over a hundred megabytes for a single file. That's far better than I expected.
It can go several subdirectories deep just fine, although this has little point, as all the songs are treated as one long, linear playlist. The sole reason for grouping each album's tracks together in a separate directory seems to be the "folder repeat" option, which confines track playing and skipping alike to the current directory only... although you still need to skip ahead a lot to get to those later albums in the first place.
The biggest problem with such a linear, non-hierarchical song menu is that without the ability to skip a whole album at a time, you can't reasonably navigate to more than the first few albums. You end up either listening to Adamski more than Hans Zimmer (or Albedo 0.39 more than Zoolook), or switching to random play and treating music like a commodity, as with radio stations, the iPod Shuffle, and streaming services, just chucking more content onto the hopper. At least it doesn't have adverts or charge you a monthly rate.
The case's labelling claims there's a microphone inside, which there isn't. It seems that, to save money, the microphone was removed, but the labelling wasn't updated. The firmware doesn't seem to have the option to record anything, either from the missing microphone or the FM radio.
Alas, none of that mattered much, as for me the whole enterprise was marred by a very distracting constant background noise. If it wasn't for that single very important detail, this would be a fun little MP3 player. I believe the issue is that my earphones and I can only handle the volume on 1 or 2 out of 31, suggesting that I just need some really high impedance headphones. My closed-back headphones had the same issue.
I tried to record a demonstration of this issue on my trusty Edirol R-09, via its line in socket, but in order to record the MP3 player, I had to crank its volume up to 31, which completely resolved the issue. It seems that needing the volume on a ridiculously low setting is quite naturally skewing its signal to noise ratio, but I don't know how to easily avoid that issue. So it seems this is fine when plugged into the line in of, say, a hi-fi, but not when plugged into headphones. At least, that was the case with my own experimentation. None of the other customers seemed to mention this issue, so it's possible my unit was a dud.
Taking it apart revealed two ICs. The largest is a Jerry Chip AK24BP2D054-51C8; the smallest is an NS8220 2431Y1 headphone amplifier. It seems the ATJ2085 days are long gone.
In short, if they can fix the volume, add the ability to skip a directory at a time, and remove the vestigial microphone label, this would be a nice, simple MP3 player. It's a widely supported format, and taking a single AAA battery, you don't have to worry about having to throw away an otherwise perfectly functional device in ten years just because its internal hardwired battery died. So that's one of Apple's more questionable decisions avoided, at least.
References
- "Hardware Specs" S1mp3.org, Oct 2005
- "S1mp3 Device Database" S1mp3.org
- "Basic User Guide" Cho, S1mp3.org, Oct 2005
MP3 players: A case for MP3 players | S1 MP3 player | iPod Mini
