Uhm … not quite 😛
1) DVS. You use timecode (actually built-in to the 3900, so no need for timecode CD) to control the track in your DJ software. In this setting the routing is:
3900 to soundcard input -> soundcard USB to PC -> soundcard output to mixer. The soundcard has a through switch, which let’s you play regular CD’s on the 3900 as well. Your SC3900 don’t have to be connected by USB.
2) Midi. You connect your 3900s with USB to your PC. You connect the sound output from the 3900s directly to the mixer. In your DJ mixer you set the output channels to both the 3900s (depending on mac or windows, you have to “aggregate” both 3900 built-in soundcards so the OS sees them as one 4-channel soundcard). Now you control the DJ software entirely with the 3900s. The tracks that are loaded into the DJ software decks is played back out through USB into the 3900 and then to the mixer.
If you use the 3900s in midi, you don’t need the soundcard. If you want to go DVS you do.
To complicate matters, the 3900 has a so-called Hybrid mode. In Hybrid mode, you use timecode to control the platters (thus doing the DVD routing, but you add USB connection too, so you can use all the other buttons (loop, cue, etx.) that are normally not available in DVS only mode.
So, it’s up to you which to pick. Midi is simplest and gives most functionality. You’ll have to see if the response from the jogs is ok for you though. Hybrid would be my second choice (find the jogs on the sc2900 to have good enough responsiveness in midi mode). Pure DVS would be my third option.
Having said that, I am sure there are plenty of others on the forums that have other preferences. I hope this made some sense and was helpful in some way.
Greetinx.
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