On Friday, November 15, 2013 12:30:52 PM UTC-5, Beloved Leader wrote:
Hi. The RioS50 mp3 player was on the market some ten years ago. The owner's manual and reviews are easily found online.
.....

Although the owner's manual and reviews are online, I have not found the details for the recharger.

I just wasn't looking hard enough. The correct voltage is revealed he

http://transistor-man.com/Altoid%20MP3.html

"The power source was 1 AA / AA NIMH battery, which was dc-dc converted to 3.3V for the devices operation."

So that's the trick. I don't think it's a new page, but I've never seen it come up before in a search.