For as long as I can remember, I have always wondered why DAPs don't have a mono setting for those one-ear moments, whether I want to share an ear with a friend or take a phonecall whilst still listening to my music. I can't see why this is not possible for even the humble cpu's of ipods to achieve on the fly. After all, it simply requires the software to add the music headed to the left and right ears together and send the resulting signal to both channels. I have a vague recollection of tape walkman's actually having this setting (altho the vagaries of analogue may have made this easier, since it would have been a hardware solution).
If nothing else, it would diminish the number of kids who travel in pairs from playing music over their phone speakers...
If nothing else, it would diminish the number of kids who travel in pairs from playing music over their phone speakers...