Closer-where is the momentum?

Unfortunately the bass is somewhere when converting to MP3 gone a little lost and the ups apparently also. The dynamics of several MP3 files is somehow not great and is not far to the quality of MP3 CDs, which I, with Windows-board resources, from the original in MP3 with only 192 kbits s have / converted. Too bad the prices at Amazon, I found good, but the quality leaves me but grab back to the original to convert these yourself for use in the car well.
Is solved in other online stores better ???