The audio conversion field is extremely crowded, many audio converters are not free of charge, or have significant limitations, the audio quality of the output file converted by them are very poor. On the other hand, there’re lots of free even open source ones that can get the jobs done without any fuss.
1, Kastor Audio Converter

Kastor Audio Converter is a small utility that will help you to convert avi, aac, ac3, ape, flac, m4a, mp4, mov, flv, mp3, mp2, mpc, ogg, wav, wma, wmv, asf, mkv and alac files to mp3( supports VBR-0 to VBR-7 ), wma, ogg( 10 quality levels ), flac( level 0 to level 8 ), wav, aac files.
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Besides that it can also rip your audio CDs to music files, it works on Windows 2000, XP / XP X64, Vista / Vista64 and Windows 7 / 7 x64. You can download it from http://www.kastorsoft.com/index_en.html.
2, WinLAME
WinLAME is a free and open source audio encoding and conversion utility. It let you to follow a step by step wizard to convert your favorite songs to most popular audio formats like mp3, wav, ogg, etc.

Features
- Support various input audio formats: WAV, MP3, MPG, MP2, OGG, FLAC, WMA, ASF, MOD, S3M, XM, IT, MTM, MO3, UMX, M3U, PLS, CUE, AIFF( Apple/SGI ), AU( Sun/NeXT ), AVR( Audio Visual Research ), CAF( Apple Core Audio File ), HTK( HMM Tool Kit ), IFF( Amiga IFF/SVX8/SVX16 ), MAT4( GNU Octave 2.0/Matlab 4.2 ), MAT5( GNU Octave 2.1/Matlab 5.0 ), PAF( Ensoniq PARIS ), PVF( Portable Voice Format ), RAW( header-less ), SD2, SDS, SF, VOC, W64, WVE, XI, etc.
- Support multiple encoders and output audio formats: MP3, WMA, WAV, Apple AIFF, SoundForge W64, OGG.

- Allow to customize the sound quality, bitrate( 64KBPS, 128KBPS, 160KBPS, 192KBPS, 224KBPS, 256KBPS, 320KBPS, etc. ), sample format, variable bitrate, average bitrate and constant bitrate depending on the encoder you selected.

- Support batch conversion.
- Allow to pause and resume the conversion process.

WinLAME works on most mainstream 32-bit Windows platforms.
WinLAME is a 4.13MB download available from SourceForge.net and SoftPedia.com.
