Since brand new, both players have not played the same track at identical speeds. To illustrate this I used tractor and hooked up both decks. With vinyl mode turned off or on and no pitch slider adjustment it should play the same track at the same speed. It shows one deck running at 121.99 and the other plays at 122.02. Its the same way when used without DVS… One deck is faster than the other. I know it seems like a small difference but its enough for the mix to not sound correct to my ears and to require a lot of adjustments keep in time. Of course the problem gets bigger when you start to deal with songs of different bpms and move the pitch slider because I can never get the decks to match in pitch. What do i have to do to correct this? I had a electronics technician replace the pitch sliders on both players. He thought that would solve the problem.
Kev, SC3900 are so similar to turntables that they also share the same issues: wow and flutter affects the playback speed.
Try this … label the platters eg: A and B
Try swapping platter A into deck B and vice Versa… see if the speed fluctuations follow the platter or stay on a particular player.