hi allsorry for the question:(but when i convert an MP3 from 128 to 192 or 256 kbps i'll have effective Kbps or i lost the quality?
There is absolutely no point in converting UP in MP3 bitrate - all it will do is make the 128k quality file take more space, and risk additional encoding loss and artifacts.
Oh, it's not just a risk.
The file will be larger and will be inferior to the original. It's not just pointless, it's a big no-no.
never ever convert a file unless its flac or wma lossless format then convert it... i stick with vbr(0) which saves space in my book same quality as 320bitrate song but the size of a 192bitrate song
FLAC and WMA lossless aren't the only safe ones.
Any lossless codec is good to transcode from. So the list is at the very least: FLAC, Monkey's Audio, LPAC, WMA Lossless, Apple Lossless...