I recently bought a DANE-ELEC DA-MP3-S0000 zMATE MP3 player. It sort of works, but the design seems to have problems with the internal power supply circuitry. Like many portable devices, it uses a DC-DC converter to step up the voltage from one AAA cell to provide about 3 volts to the rest of the electronics. What happens is the thing eats a AAA in a very short time and then stops. It behaves just like a sick DC-DC converter. For example, when I feed the device a little bit more voltage, it uses a lot less current. But when it is running on a AAA battery, it consumes peaks of 250mA, which causes voltage of the AAA cell to dip, which causes the DC-DC converter to suck more current, and so on, in a downward spiral. Maybe I will bring this one back to the store. I could live with the fact that it is USB 1, but the power supply problem makes the device useless.

Update: I now have a Panasonic SV-MP010 MP3 player. It runs on one AA battery and Panasonic claims 80 hours battery life. According to my measurement, the device consumes 23mA from a AA battery that is about 50% used. Alkaline batteries are useful for about 2Ah (reference) assuming that the DC-DC converter in the device can operate down to 1V. About 87 hours would be expected if the current stays at 23mA, but one expects the current draw of the DC-DC converter to increase as the battery voltage decreases. So 80 hours of battery life seems like a reasonable estimate. This is quite impressive. And the player sounds good. One odd thing was that FreeBSD didn't want to mount the Panasonic as a USB mass storage device until I formatted it using newfs_msdos. But after that it has been fine.