i export my tracks from rekordbox to an sd or usb device but when i mix two tracks the same bpm 0.00% pitch they stay good in time but when i mix two tracks with different bpm s 123 two 125 and i pitch the slower track to 125 + 1.60% they don t stay in time for then seconds and then i have make  corrections and when i set an quantize loop 8 or 16 beat loops then stay only for 5 seconds in time why i have this problems and are this  the cdj 2000 (are they not so precise?)or is the audio format  what i use the problem?

Any CD Player device will have a digital pitch control which only offers a finite level of precision.  In the case of Pioneer, the best precision we can attain is to the 0.02% increment (on 6% range setting).  By nature of this fact, a CD Player will require more manual adjustments than a vinyl turntable (in theory) because of the limitations of digital vs. analog pitch control.

Secondly, it is entirely possible that the tracks you are attempting to mix have a slightly variable tempo.  I come across music like this fairly frequently, where as the track progresses, the BPM may change.  For example, a track might start out at 125.00 BPM, but by the end of the track it has slowed to 124.97 BPM.  I have confirmed that this does happen sometimes, and my solution has been to process these tracks in Ableton Live.  I warp the track to a constant tempo and then render it to a new audio file which has a perfectly stable BPM.

This does not happen all the time, but I promise you that I do come across tracks which exhibit this kind of behavior.  It drove me nuts until I figured out what was happening.  You might want to inspect your tracks for unstable tempo.  To check for this, do the following:

1.  Load new track in Rekordbox and analyze with Normal mode.

2.  Open the grid adjustments drop-down arrow so that you can see the blue beat grid on the waveform.

3.  Find the first down beat of the track and make sure the blue beat grid is aligned to it correctly.  There is a metronome feature which you can use to hear the beatmatching of the grid to the beats of the music.  I use this as a fine-tuning guide in combination with the visual marker.

4.  Once you have lined up the first beat, you need to skip ahead to the middle of the track and check that metronome and see if it is still on-beat.  If it is one beat, then click ahead to the end part of the track and check again.  If the grid is not on beat when you skip ahead in the track, then you should use the tempo adjustment buttons to stretch or squeeze the blue grid either wider or tighter to make it line up to the beats again.  Once you have lined up the blue grid, skip ahead to a future point in the track and see if the tempo drifts off beat again.  If it is still on beat, then you have a track with stable tempo.  But if it goes off again, you will know that the track is changing tempo over time.

If you get to the end of step 4 and you have a track which seems to drift in tempo over time, then you have 2 choices for how to handle this situation.

Choice 1  -  Use Rekordbox to make incremental adjustments to the tempo at several points in the track.  There is a button on the grid adjustment section which will allow you to freeze the grid for all points BEFORE that point, and then allow adjustments only to later portions of the track.  So you can use this feature to line up the beat grid on the first part of the track, and then go to the next part and adjust the beats again until they line up, then lock down another beat marker and adjust some more after that..... until you have all the blue beat markers lined up.  If you do this, just keep in mind that Rekordbox is not changing the tempo of the track.  It is just changing how to BPM display shows the tempo rate.  So as you plat your track on the CDJ, you will see the BPM display change the tempo reading as the track plays over time.

Choice 2  -  Use software like Ableton Live (or any production suite which can change the tempo of the music) to create a copy of your music file with a constant BPM.  By doing this, you will be fixing the errors in the tempo and there will be no need to make incremental adjustments to the blue grid in Rekordbox.  Once you have loaded the new audio file, the blue grid should line up perfectly without needing any of those Stretch or Squeeze adjustments to the blue grid.  This means that when you play your music on the CDJ, the BPM display will stay constant throughout the track.... and in theory, you should need fewer platter adjustments.  (Fewer, but you will probably still need to correct some)  Like I said above, the CDJ players have digital pitch controls which cannot always give you perfect beatmatching with zero need for corrections.  There will almost always be a need to correct some, especially if you have a long-mix style.

@ gavin  sorry i mean i allways look that the bpm is 123.0 bpm  pitch range 0.00% and the other track 123.0 bpm pitch down from 124 bpm - 0.80% and so i mix my set but when i go and want to mix 2 tracks with 123.0 bpm and 125.0 bpm pitch the faster track at 123.0 bpm pitch range -1.60% i need to make few more corrections then with 1 bpm different  i play tech house and deep house and i like to make very long transitions but  i don t like when i hear in my recorded set allways the correction it sounds very ugly and what i notice that when you make quantize beatloops the track very fast go off beat 

@fuse promote hey thank you for the answer i try this with rekordbox to adjust the beatgrid but in abelton this with the wraping story feels better i wraped my hole playlist in abelton mp3 320 kbps and exported to aiff 24 bit then in rekordbox analysed in normal mode and than to my sd card it feels little bit better but its not perfect  :-) the tracks are warped and on a constant bpm this little bit maybe are the cdj 2000 who drift ? i don t now? and why is the best precision on 6% pitch range 0.02% better where we can go 0.01% 0.02% 0.03% and not 0.02% 0.04% 0.06% maybe with the next cdj 2000 update,i started playing with technics 1210 mk2 and it fell s better  that the tracks who i mixed stay more in time than when i mixed with  the cdj 2000 and the are moderner and more expensive 

i have the new update on the cdj 2000 but i don t use the master tempo is it better to mix with master tempo on the master tempo was not usabel be four  

and jet with  the new firmware is it better ?

I have tested Master Tempo with the new firmware and do believe it works better now than on previous firmware versions.

However, I personally do NOT use the Master Tempo feature.  In fact, I have never used Master Tempo on any previous Pioneer CD player.  It's just not a feature that I find useful at all.  I have always noticed over the years that the Master Tempo feature causes distortion to the audio quality when used at the far extreme range of the pitch control.  To me, preserving the audio quality is more important than having the pitch of the music perfectly locked.  I never had this option when I learned to mix on vinyl, so I don't feel like I've lost anything y not using the feature with CDJ players.

i don t mix with master tempo on and i choose only track with  max +2bpm  -2bpm bigger different i notice the cdj can hold the tracks in time for 5 sec. without correction 

@jambapark > I don't want this to sound rude at all, but if 2 tracks fall out of sync after 5 seconds, then they aren't correctly beat matched. Using the BPM readouts should only be used as a reference, and you should always mix with your ears overall. :)

The short answer to the original question in this thread is WAV or AIFF are the best formats to use with the CDJ-2000.  Period.

I just spent nearly an hour testing another forum member's MP3 files which had glitches in them that caused instant trainwrecks when attempting to mix them.  After making copies of those MP3 files and rendering them as AIFF files from Ableton Live, the music mixed perfectly and the glitches were gone.  I don't know what the cause of the problems were with those MP3 files, but I do know for an absolute fact that rendering those files to AIFF solved the problem.

In addition to the above-mentioned glitch issue, I also had my very first CDJ-2000 player freeze up on me while playing one of those MP3 files.  I have always used AIFF or WAV files for many, many years and I had never seen my CDJ-2000s lock up like that.  I am very confident that again it was the fault of the audio file and not the CDJ-2000.

The bottom line is that MP3 files can easily be corrupted or compromised in quality.  My best suggestion for everyone is to use uncompressed audio formats for your DJ music.

@jambapark > +/-2BPM @1.60% means you're using 10% Tempo adjustment, correct?

Which I'm not sure why you use +/-10% when you only ever mix tracks +/-2BPM's apart. The 6% Tempo adjustment would provide you with greater accuracy.

Anyways, I've noticed sometimes it takes an adjustment of +/- 0.10% at the 10% Tempo adjustment in order to change the BPM by 0.1. That being said, just because the BPM's display the same number to the decimal point, doesn't mean they are both exactly the same. Such as what @Gavin mentioned "which obviously, is very close, but not equal".

@jambapark > My apologies about that first part of my last post. I wasn't talking about the same thing. lol I need sleep. ;)

Can't comment on what's happening with the looping.  I have never used looping on any Pioneer player.  It's not a feature that I have any use for.

There are 2 reasons why I use Repitch mode in Ableton Live when I am warping my full-length tracks:

1.  Repitch mode offers the highest sound quality for all of the warping methods in Ableton Live.

2.  Since I am not trying to drastically change the tempo of the track, then Repitch mode is best suited.  For example, I am only using Live to make a minor correction to an unstable tempo.  I am not trying to take a 105 bpm track and make it 125 bpm.

Beats and Transients modes are not acceptable for warping entire tracks.  Those warping methods are designed for short clips, like a 4 bar loop.  They cause excessive, audible distortion to the sound when used on longer clips or full-length tracks.

Repitch mode is the highest sound quality warp method for Ableton Live, and it is the best to use with a full-length track.

Complex Pro & Complex modes can also be used with full-length tracks.  If you are trying to change the tempo of a track by a large amount, then these two modes will preserve the pitch of the track while adjusting the tempo.  These modes are essentially Live's version of Pioneer Master Tempo button.  If you need to warp a track to a different tempo but want to preserve the pitch of vocals, then use one of these two modes.