An m3a file extension is related to the Enhanced M3U playlist file format used by JukeBox Decoder.
M3A file extension - Enhanced M3U playlist
What is m3a file? How to open m3a files?
The m3a file extension is used by JukeBox Decoder for a special kind of M3U playlists enhanced by some additional data.
The JukeBox Decoder seems to be obsolete product without support from developer or producer.