How big difference is there between lossless formats like flac/wave and an ordinary mp3 file (lossy)? Is there any benefit in stuffing your iPod full of lossless audio? Will the improvement with lossless audio be significant enough to justify the larger file size? If you only got a limited amount of songs on your iPod (or if you by chance using a classic version) it might not be any concern at all. Neither if you running a USB harddrive etc etc. However if you're using a iPhone or iPod touch the disk space is kinda limited, especially if you got over 2000 songs stored on it. No way I got enough space for lossless (and I refuse using a iPod classic btw...)Alternitive 2: Using lossy formats. Mp3 and AAC are two formats that's commonly used and supported by many headunits out there. Lossy means something been taken away from the original file. A lossy format compresses the audio file with different algorithms to reduce file size, depending on compression level and format a lossy audio file might be 5-10 times smaller than a lossless (file size differs between lossless formats as well).So what's been taken away? How audible is it? There are definitely differences between lossy formats and there's a big audible difference between bitrates (higher compression = lower bitrate), at least at the lower range. For the record there are no audible or measurable difference between lossless formats. The very definition of lossless is that they have retained all available information from the source file. Some people claim to hear differences between flac and wav files, well... there are none.Using lame codec for mp3s. You can use variable bitrate (VBR) and constant bitrate (CBR). VBR is probably the better choise but I chose CBR for testing purposes now. VBR v0-v2 use bitrates around 200kbit+ and are usually 'good enough'. AAC is another format that claim higher compression than mp3 with retained sound quality. Not used it much, did try a 128k AAC vs a 128k~ avg equivalent VBR mp3. Didn't hear that much difference between them, never measured them though...Did some measurements on how different bitrates compare to the lossless source file and subtracted the 'missing' information and compared it as a waveform to the original file. Tested myself with a ABX plugin, had difficulty discerning any differences above ~200kbit/s or so. Listened through pair of "decent" Sennheiser headphones from a SB Audigy4 Xtrememusic soundcard. The test only tells you how much my hearing sucks so it's not a "fact"...Made a neat little graphs of the result, tried 5 different songs (flac vs X bitrates). Two tries with each song equals 10x A/B choices/bitrate. AS you can see results were random once I hit 224kbit/s. Now that just me, but you should do the same, test yourself and see if you can hear the difference.(Actually it was version "3.99.5", audacity lied xD)And here the measurements (Audio file: Eagles - Hotel California (Unplugged).This is a spectrogram of the different bitrates, 192k CBR/256k CBR and FLAC. The lack of "blue" stuff at the top of the mp3 spectrograms indicate that high frequency information has been removed from compression. 320k doing pretty good vs the flac.These two is another representation of the spectrogram. This shows the lowpass function of the mp3 file at ~20kHz (above - the 320k CBR codec). Note that the graphs are scaled differently ^^This is the subtracted "lost information" from a flac to 320k CBR conversion. Compared to the orginal waveform it ain't "that" much. It's very audible if you listen to the extracted audio only, but quite inaudible (IMO) once mixed with the flac (subtraction mixed).It can easily be done by phase inversion and mixing two tracks in Audacity fyi.