I have an 8GB Sansa Fuze with 01.01.15F Firmware. I did not use the Sansa earphones, I use some better ones from AIWA and SHURE.
With some 128kbps CBR MP3 music files I get a low frequency popping sound at playback some seconds after the backlight goes off.
When I press the middle button to turn the backlight on, the popping sound disappears until the backlight goes off again.
The popping sound is like pop-pop-pop-pop… with approximately 131.5ms between the pop’s.
It looks like during the pop the Sansa held its headphone output at a constant level for a duration between 1.8ms and 3.8ms.
This constant level is far away from clipping and it seem it is random respectively it is the actual music level when the phenomenon occurs. (I got this values with the help of a LeCroy oscilloscope.)
When I play the music files on a PC with Software MP3-players (foobar2000 or media monkey) and the same earphones, there is no popping sound during playback.
I have downgraded the Sansa Firmware back to 01.01.11F and the popping sound disappears on the Sansa.
So it looks like there is a bug in the actual 01.01.15F Firmware.
I make a big effort to investigate this effect and have tried a lot of thinks with this kind of music files.
The popping sound also appears with a fresh Sansa self-formatted memory with only one file at the Sansa.
I tried 5 seconds and 15 seconds backlight turn off time.
I have a lot of 128kbps CBR MP3 files which show this effect. These MP3’s are compressed with different encoders.
The files have only ID3v2.3 ISO-8859-1 Tags, but with other Tags the behaviour is the same.
Today I have already send one MP3 music example file and some oscilloscope screen-shots with this description to email@example.com.
(Remark: firstname.lastname@example.org is not working, I got an error message back.)
The message subject is: “Sansa Fuze FM 8GB Bug with 128kbps CBR MP3”
I hope you will fix this bug in the next, hopefully coming soon, Firmware release because it is really annoying also at louder music passages.
I am German so please excuse my English.
There is also an bug in the German translation for “Empty”.
Instead of the correct translation “Leer” the wrong translation is “Leeg”.
(I think this is the Dutch translation, not the German.)
It is used e.g. in Playlists (Wiedergabelisten), GoList (Wiedergabeliste) when the list is empty.