Knowing about digital audio files is a must for a DJ in this day and age. If you want your sets to sound as good as the pro's you must have all of your tracks in high-quality audio!
A full quality MP3 file weighs in at 320 kbps, this number is dramatically different to that of a WAV or AIFF file. However, the difference in audio isn't. BUT! As soon as you go below a full quality MP3 the quality drops fiercely. Even though an iTunes file at 256 kbps seems like a tiny drop from 320 kbps in comparison to the 1411 kbps of lossless audio files, the drop in quality is dramatic and easily noticed. MP3 files at 128 or 192 kbps (eg, Youtube rips/dodgy downloads) are significantly worse again. The difference is easy to hear! Test this out by ripping an MP3 from youtube of a track you own in high quality and play one after the other. Even the untrained ear could hear the difference between the two!
The charts below show a measured difference of the same audio file in both WAV and MP3. You can see everything is very similar, the only obvious difference is the frequency drop off above 16khz which is outside the range of human hearing.
Being sure your track collection doesn't contain any low bitrate files is extremely important. If you're playing a set containing a mixture of full quality and low quality tracks the difference between them will show when mixing between the two. Even if the low bitrate files have been gained to the same volume as the higher quality ones, you will not have the same weight in the bass, shine in the top end and generally speaking the track will sound very 'flat' making them appear a lot quieter and weaker.
Finding new music and getting hold of full quality audio files is a VITAL part of any DJ's life. So where can you head to when iTunes only offers low quality files.
Beatport is one of the most popular sources of new music and high quality tracks. This online music shop is specifically geared towards DJ's only supplying high quality audio files. They have great top charts specific to genre, playlists from named DJ's and decent recommendations when browsing the site.
Trakitdown also specialise in high quality tracks. This online music shop is again aimed at DJ's only supplying high quality audio files. These guys also run a top chart of their own which is worth keeping an eye on as it does tend to vary from the Beatport listings.
Bleep are a really great source of independent music. They tend to push the forward thinkers and innovators of new sounds (Think Jamie xx, Bjork, Kode 9 and Floating Points) making them a solid source for standout new tracks. As well as selling high quality digital files they also sell vinyl, merchandise and small amounts of equipment.
Bandcamp has to be my favourite site of the bunch. Being completely independent means that a significant amount more of the money you pay makes it to the artist. You will find independent labels such as Shogun Audio, Exit, Wah Wah 45's and Tru Thoughts, all of which have major artists signed who sell out shows globally! Independent does not mean small!
My favourite features on Bandcamp are the ability to stream tracks and albums in full before paying for the download, being able to download in whatever quality you wish (including FLAC and Ogg Vorbis for the sound nerds) at absolutely no extra cost, and the 'buy it now - name your price' option. If you come across this don't feel bad about entering 0. The artist chose for this to be an option, they could have chosen to put '50p or more,' but if you are able to support them then do! Even if its only £1 for a full album. All this makes Bandcamp one of the best places going to search for new music AND you can find a lot for free!