Any "copying," including ripping a CD you own, transcoding an audio cassette you own, etc. is, strictly speaking, in violation of copyright. You don't have a license to the music, you only own the medium. There's nothing in the purchase of a CD, LP, nor cassette, including printed on the medium, packaging or inserts, granting you any type of license. The copyright holder (author) holds an exclusive license and only they can transfer or grant additional licenses.

Even playing a digital recording on an MP3 player or computer is technically copying the song - it's being cached at least to memory which is a copy of the file on disk. Playing in a browser might further leave you with multiple disk-based cache copies as well.

In the US you have "Fair Use" which can allow an individual to do "things" with the copyrighted work that have not been expressly permitted to them by way of a license. Such a concept may exist in other countries, but I suspect some countries don't have any such provisions, backed by case law or not. The fair use concept doesn't expressly cover making digital copies of your analog recordings (format shifting).

Copyright and Fair Use FAQ (US)

Converting tapes to MP3 - mainly for a few links to EFF etc..

Between Lawyers Blog: Fair Use, Personal Use and the Digital Copyright Morass