If your RAR file comprises MP3 files, for example, you could open the RAR file, not convert it, to get the MP3s.
Ọ bụrụ na faịlụ RAR gị nwere faịlụ MP3 , dịka ọmụmaatụ, ị ga- emepe faịlụ RAR , ọ bụghị igbanwe ya, iji nweta MP3.