cause a mp3-player (standard!) handles both - vbr and cbr - in the same way:
a song is divided into frames and every frame has a constant bit rate and a constant length of 0.026 seconds
so there is no difference between e.g.
128kbs,frame1;192kbs,frame2;... or

so i can only suggest to check the quality of u recordings or u mp3-player
) does it sound better on pc?
) does cbr sound really better on the mp3-player?
) are u headjacks working?

i know it - everything sounds stupid - but normally it can't be the player